IB RARY . F -TH E U N IVLR-S I'f-Y' OF ILLINOIS 630.7 Utt no.49-60 AGRICULTURE NOTICE: Return or renew all Library Materials! The Minimum Fee for each Lost Book is $50.00. The person charging this material is responsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for discipli- nary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN L161 O-1096 UNIVERSITY OF ILLINOIS Agricultural Experiment Station URBANA, JULY, 1898. BULLETIN NO. THE CHEMISTRY OF THE CORN KERNEL 1 . . INTRODUCTION. The object of these studies on the chemisty of corn 2 is to trace its historical development, to bring together from many sources the existing knowledge of the subject, and, if possible, to add thereto in certain lines where our present knowledge seems most defi- cient, omitting fields wherein other investigators are known to be engaged. With the single purpose of being faithful to the history of the subject, I have felt equally free to point out misconceptions, erron- eous conclusions, or real advances of past investigations. The subject has naturally divided itself into two parts: i st. The proximate composition of corn, which has a very prac- tical significance as indicating its value as food for man and domestic animals and as raw material for various manufacturing purposes. 2nd. The complete and exact composition of the different groups of substances found by proximate analysis, a matter of more purely scientific interest, though not without phases of economic importance. ACKNOWLEDGMENTS. I acknowledge with pleasure and gratitude my indebtedness to the Department of Chemistry of Cornell University for the opportunities and privileges which have been freely accorded to me. I am especially grateful to Professor G. C. Caldwell, under whose direc- tion these studies have been carried on, and who has been to me a con- stant source of counsel and encouragement. 1 Presented to the Faculty of Cornell University as a thesis for the degree of Doctor of Philosophy, June, 1898. 2 Indian corn, maize; Ger. IVillschkorn, J fat is; Fr. metis: Sp. maiz ; from Hay- tian tnahi's. (Zea Mays L.) 132 BULLETIN NO. 53. Bizio found corn to contain oil, which had not been discovered by Gorham. The substance, hordein, was so called by Bizio because of its similarity to the substance which had been obtained from barley by Proust 1 and so named by him; which, however, was after- ward shown by Guibourt 2 to be merely a mixture of hulls and cellular tissue; and the hordein as found by Bizio was doubtless a mixture of these fibrous substances with considerable amounts of adhering starch and protein. Probably the first work from the record of which the total amount of nitrogenous matter can be very approximately calculated was that of Bousingault, published 3 in 1836 upon the total nitrogen content of corn. By combustion with copper oxid .617 grammes of corn (con- taining 18 per cent, of water) were found to yield 10.3 cubic centi- meters of nitrogen gas measured at 9 degrees and 738 millimeters. By computation I find this to be equivalent to 2.39 per cent, of nitrogen in the dry matter, and by using the factor 6.25, this gives 14.9 per cent, of protein. In 1846 Horsford reported* a complete ultimate organic analysis of corn and then by an ingenious use of the formula which had been worked 5 out for the average composition of several proteid bodies, as egg- albumen, gluten (Kleber) of wheat, rye, etc., he calculated the ultimate composition not only of the nitrogenous matter, but also of the nitro- gen-free organic matter. Using the factor 6.375 for converting nitrogen into protein, and having determined the percentage of mineral matter he gives corn the following composition: Carbon , 8 . 07 Hydrogen i . oo Nitrogenous matter 14.66 Nitrogen 2.30 Sulfur 16 Oxygen 3.13 Carbon 37.38 Non-nitrogeuous organic matter. 84. 52 Hydrogen 5.61 Oxygen 41.53 Mineral matter 1.92 1.92 ^nnales de Chimie et de Physique (1817), [i] 5, 337. 2 Jahresbericht [Berzelius] iiber die Fortschritte der physischen Wissenschaften (1831) 10, 202. 3 Annales de Chimie et de Physique (1836) [2] 63, 239. 4 Annalen der Chemie und Pharmacie (1846) 58, 182. "'Soberer, ibid. (1841) 40, i; Jones, ibid. (1841)40, 65; Heldt, ibid. (1843) 45, 198. 1898.] CHEMISTRY OF THE CORN KERNEL. 133, A very extended article by J. H. Salisbury on the general subject of corn was published 1 in 1848. It included a report of considerable chemical work, done by such imperfect methods as nearly to deprive it of permanent value, as will appear from the following analysis of two* samples of corn kernels : I. 2. Albumen 9.29 4-64 Zein 6.73 3.98 Casein i . 44 .09 Dextrine or gum 5-94 3-53 Fiber 12.09 .96 Matter separated fromfiber by weak potash solution, 7.80 6.48 Sugar and extract 13.27 14.42 Starch 38.28 60 . 92 Oil 5.18 4.98 The methods employed by Salisbury were in the main similar to those of the earlier investigators and are briefly indicated as follows : The powdered corn was washed with water which was decanted. The residue extracted with alcohol and dilute potash water gave the fiber. The matter held in suspension in the water was collected, washed with alcohol and noted as starch, the residue from the evaporation of the alcohol became a portion of the "sugar and extract." The turbid water from the starch determination was heated and the coagulated matter called albumen. In one portion of the filtrate the "casein" was precipitated by acetic acid, and the "dextrine or gum" by alcohol after partial evaporation. In a second portion the "casein" and "dextrine or gum" were together removed by alcohol and another portion of "sugar and extract" obtained by evaporating the filtrate to dryness. The zein and oil were extracted from the corn by alcohol and separated by ether after evaporation of the alcohol. Following Salisbury's work proximate analyses were reported by Poison 2 , Poggiale 3 , Stepf , Payen 4 , and also by the renowned and but re- cently deceased R. Fresenius 5 . 'Transactions of the New York State Agricultural Society (1848) 8, 678; Ameri- can Journal of Science and Arts (1849) [2] 8, 307. -Chimic. Gazette (1855) 211 ; Journal fiir praktische Chemie (1855) 66, 320. 3 Jahresbericht [Leibig und Kopp] fiber die Fortschritte der Chemie (1856) 809. 4 Journal fiir praktische Chemie (1859) 76, 88, 5 Landwirtschaftliche Versuchs-Stationen (1859) 1, 179; Jahresbericht [Hoff- mann] uber die Fortschritte auf dem Gesammtgebiete der Agricultur-Chemie (1859) 2, 7 6. 134 BULLETIN NO. 53. [/"6'> The following will serve as illustrations of the results : Poison. Poggiale. Fresenius. Water n.8 dry 13.5 dry 13-46 dry Ash 1.8 2.04 1.4 1.62 1.58 1.83 Protein 8.9 10.09 9-9 xl -44 10.04 11.60 Oil 4.4 4.99 6.7 7.75 5.11 5.90 Fiber 15.9 18.03 4- 2 4.62 1.58 1.83 Sugar 2.Q 1 3.29 2.33 3 2.69 Starch 54-3 61.56 64.5 74-57 65.90 76.15 In 1869, Atwater reported* the following results from a study 5 of the proximate composition of corn : Early Button. Common yellow. King Philip. Ash 1.66 1.46 1.77 Protein 10.46 10.86 13.16 Fat 6.16 4-94 4-93 Fiber 2.74 2.68 2.45 Sugar 3.26 5.34 3.38 Gum 4-59 2.64 5.32 Starch 7 1 1 3 72.08 68 . 99 The protein was estimated by multiplying the total nitrogen by the factor 6.25, a method which had come into general use, and which has already been referred to under Horsford's work. Sugar was estimated by Fehling's method from the aqueous extract, and the gum is the difference between the sugar and the dried aqueous extract. The oil is the ether extract. Fiber was determined by extracting with dilute acid and alkali, essentially the method employed by Gorham nearly eighty years ago, and in general use among agricultural chemists of to-day, having been known under various names, as PeligotV, Henneberg's, or the Weende 7 method, the last being common at the present time. Starch was estimated by difference. Closely following Atwater's work numerous analyses were reported by European chemists. In the group of carbohydrates only the fiber was determined, the remainder being estimated by difference and re- ported under the negative and indefinite heading "nitrogen-free extract" for which I have recently proposed 8 to substitute the more definite and logical term carbohydrate extract. *and gum. 2 and loss. 3 dextrine. 4 W. O. Atwater The proximate composition of several varieties of American maize Thesis for the degree of Doctor of Philosophy, Yale College (1869) ; Ameri- can Journal of Science and Arts (1869) [2] 48, 352. 5 The analysis of a sample of sweet corn also reported is omitted. e journal fiir praktische Chemie(i85o) 50, 261, 7 Landwirtschaftliche Versuchs-Stationen (1864) 6, 497. 8 University of Illinois Agr. Exp. Station Bulletin (1896) 43 1898.] CHEMISTRY OF THE CORN KERNEL. 135 The following table gives a number of the results obtained, all being reduced to the basis of dry matter : Carbohydrate Analyst 1 , Ash. Protein. Fat. Fiber. extract. Dietrich 3. 19 13.88 5-59 2.86 74.48 Nessler 4-53 8.81 5.87 6.24 74-55 Nessler 3.20 6.41 6.17 6.54 77-68 Nessler 3.98 10.01 6.25 5-35 74-4 1 Kreuzhage 1.70 13-03 4-79 i-74 78.74 Honig und Brimmer 1.50 9.00 4.16 1.58 83.76 Honig und Brimmer 1.42 10.35 4-36 1.55 82.32 In 1883 Richardson 2 made a compilation of analyses of corn grown in various parts of the United States during the years 1877 to 1882. The following table shows the number of samples analyzed and the aver- ages of the analyses from each state represented. All dry matter other than ash, protein, and oil I have grouped under the general term carbohydrates. This is done for several reasons, i. We are consider- ing not complete but proximate analysis. 2. Ash, protein, fat, and carbohydrates constitute distinctly different groups with well known in- dividual properties or characteristics as to use, value, etc. 3. The amount of fiber in corn is too small to warrant its determination ordi- narily, even if it were known that its value differs slightly from that of other carbohydrates, the pentosans, for example. 4. The limit of error in fiber determination is wide and not only appears in the fiber itself but also in the carbohydrate extract (so called nitrogen-free extract.) 5. These data become more readily comparable with my own analyses which are herein reported without fiber determinations. Samples. Ash. Protein. Fat. Carbohydrates. New Hampshire 1 1 Vermont i Connecticut 13 Pennsylvania.- 5 North Carolina 2 Kentucky i Tennessee i Indiana.. . i .76 12.98 6.10 79-i6 .59 ii. 10 6.16 81.15 73 n-75 5-27 81.25 55 9-65 5-67 83.13 ,50 12.03 5-43 81.04 .62 10.62 5.77 81.99 33 10.05 5-51 83.11 .44 11.84 5-49 81.23 Michigan 12 1.67 12.83 5.70 79-8o Missouri 26 1.83 11.48 5.75 80.94 Kansas 6 1.69 n-53 5-53 81.25 Colorado i 1.68 10.95 6.32 81.05 Texas 20 1.59 11.61 6.09 80.71 Oregon i 1.61 8.68 7.80 81.91 Washington i 1.67 9.36 6.39 82.58 Mexico 3 J .75 IJ .44 6.06 80.75 General average 1.69 11.63 5-78 80.90 ^ahresbericht [Hoffmann] iiber die Agricultur-Chemie (1872) 15, 10; (1876) 19, 7. 2 U. S. Dept. of Agr., Division of Chemistry Bulletin (1883) 1. 136 BULLETIN NO. 53. The following are some of the conclusions which Richardson draws from his data : "There is apparently the same average amount of ash. oil, and albuminoids, [protein] in a corn wherever it grows, with the exception of the Pacific Slope, where, as with wheat, there seems to be no facility for obtaining or assimilating nitrogen. "Corn is, then, an entirely different grain from wheat. It maintains about the same percentage of albuminoids under all circumstances, and is not affected by its surroundings in this respect. "Only two analyses have been made from the Pacific Slope and more are needed for confirmation, but as the two analyses, like those of the wheats grown there, are low in albuminoids, it may safely be assumed to be a characteristic of that portion of the country." These conclusions scarcely appear to be warranted from the data. By computation from the 114 analyses of corn, I find the total varia- tion in protein to be 63.6 per cent, of the average amount determined; while from the 260 analyses of wheat referred 1 to by him it is only neces- sary to exclude 5 analyses to bring the total variation in protein to 60. i per cent, of the average amount determined. Or if we take the averages of the 10 highest and the 10 lowest results on the protein of 1 14 samples of corn, 12.34 per cent, and 8.19 per cent., respectively, we find the difference, 4.15 per cent., to be 40 per cent, of the general average; while with the averages of the 25 highest and the 25 lowest results on the protein of 260 samples of wheat, 14.97 per cent., and 9.28 per cent., respectively, the difference is 5.69 per cent, or 48 per cent, of the general average (11.95 P er cen t.). In other words the variation in the corn is only one-sixth less than that in the wheat. It may be noted that if we include the analyses of sweet corn (all varieties of wheat are considered) the variations in the protein content of corn exceed those in wheat. Jenkins and Winton's compilation 2 shows the protein content to vary more in 208 samples of corn than Richardson found in 260 samples of wheat. As to the assumption regarding the Pacific Slope it may be pointed out that the table of analyses from the different States shows the average of 5 analyses of Pennsylvania corn to agree well in percentage of pro- tein with the single analyses from Oregon and Washington. The aver- age of 12 analyses of corn from California reported in 1884 by Richard- son 3 shows practically the same percentage of protein as the general average for the United States. In 1886 Flechig 4 made analyses of 14 different varieties of corn, 'U. S. Dept. of Agr., Division of Chemistry Bulletin (1883), 1. 2 U. S. Dept. Agr., Exp. Station Bulletin (1892) 11, 100. 3 U. S. Dept. Agr., Division of Chemistry Bulletin (1884) 4. Landwirtschaftliche Versuchs-Stationen (1886) 32, 17. 1898.] CHEMISTRY OF THE CORN KERNEL. 137 all grown under uniform conditions of weather, soil, and fertilization. If we omit a variety of sweet corn 1 the following are his results:'' Variety. Ash. Protein. Oil. Carbohyrates. Jaune HStif d'Antonina 2 9 12.63 S 4O 80 68 Rother Hiihnermais .43 1 1 06 S 80 80 71 Weisser steirischer si 10. so c 32 82 67 Weisser ungarischer .63 q 88 6 21 82 28 Canquatino .48 9.88 S S2 8^ 12 Tiirkischer vierzigtiigiger 73 9.69 s.88 82.70 Canadischer aus Ungarn .58 q CQ 6 oo 82 Q2 Bunter Augustmais .44 Q. SO s 02 84 O4 Friih. Amerik. Bernsteinmais .42 9 J 9 S .7S 8s 64 Friiher Badischer .46 9.06 S.43 84 .OS Blanc hiitif des Landes .60 9.00 6.22 83.18 Improved King Philip 54 8.95 S.43, 84.08 PaDaeeienmais. . . is 8.60 s.88 84.08 In view of the fact that reference has already been made to the wide limit of error in fiber determinations, it may be noted here that the total variation on the final results for fiber as reported by Flechig on the 13 samples of corn is from 1.23 per cent, to 1.86 per cent., while the variation in the separate determinations made on a single sample is from 1.26 per cent, to 1.83 per cent. It is also observed that Flechig's results indicate protein as the most variable constituent of corn grown under uniform conditions. Since the establishment of the experiment stations in the United States the number of proximate analyses of corn has been greatly increased*, but in the main the analyses have been made for special pur- poses (as in feeding experiments) other than a study of the corn itself, and upon samples whose history was unknown or unnecessary for the object in view. Only one series of these analyses will be discussed in this connection. ^n 1893 the Connecticut Experiment Station published 4 the analyses of 90 samples of corn grown in 1892 in various parts of the state from about 75 differently named varieties, and under exceedingly varying conditions of weather, soil, cultivation, fertilization, etc. If we omit one sample of sweet corn, and one sample which was injured by hail before maturing, the following are the five highest and the five lowest results from all determinations of each constituent; also the general average of all analyses: 'Sucre ride'. '*A few errors were found in Flechig's summary which I have corrected from his analytical data. Fiber is included in the column headed carbohyrates. 3 Especially by U. S. Dept. of Agr. and Stations of Conn., Mass., 111., Vt. and N. J. 4 Conn. Agr. Exp. Station Annual Report (1893). '38 BULLETIN NO. 53. Ash. ist highest 2.10 2nd i .go 3rd " 1.86 4th " i. 80 5th " 1.79 ist lowest 91 2nd " 98 3rd " i .00 4th i .01 5th i .04 General average i . 39 Protein. Fat. Carbohydrates M-53 6-39 85.93 14.04 5-97 85-14 13.86 5-95 85-07 13-33 5-95 84.67 13-29 5-95 84.63 8-33 3.15 78.56 8.69 3-55 78.85 8.79 4.21 78.99 8.82 4.28 79.26 8.25 4-31 79.85 II .63 5-27 81.71 The compilation 1 of Jenkins and Winton gives the average compo- sition of dent and flint corn as follows: Samples. Dent ................. 86 Flint .................. 68 General average ........ 154 Ash. Protein. .S ii. 8 ii. 6 Fat. 5-6 5.6 5-6 Carbohydrates. 81.2 80.9 81.1 By mechanical means the corn kernel has been separated into four different parts. These may be designated (fig. i 2 ) as (a) the coat, or hull, of the kernel, (b) the hard glutenous layer underneath the hull, much thicker at the sides than at the crown, (c) the chit, or germ, and (d) the starchy matter constituting the chief body of the kernel. It has never been found possible to make such a separation with even approximate accuracy, the separation of the glutenous layer from the starchy portion being especially difficult. On this basis Salisbury 3 gives the following percentage composi- tion of the kernel with the proximate composition of the" different parts reduced to the dry basis: 'U. S. Dept. of Agr., Exp. Station Bulletin (1892) 11. 2 l am indebted to Director Voorhees, N. J. Agr. Exp Station, for the use of this cut. 3 Trans. N. Y. State Agr. Soc. (1848) 8, 678. FIG. i. Glutenous Starchy layer. portion. Germs. 66.63 18.04 ii .03 43 .61 14.05 7.65 2.74 21-39 2.87 3-07 30.26 89.05 93.58 34-30 1898.] CHEMISTRY OF THE CORN KERNEL 139 Hulls. Percent 4.30 Ash 4 . 56 Protein 1 Oil Carbohydrates 2 In a microscopic study of the corn kernel Haberlandt 3 observed that the germ contained a large amount of oil while- in the remaining por- tions of the kernel no oil was apparent. Acting upon this Lenz 3 under- took an analytical investigation of these portions. The germs were carefully removed from the kernels by mechanical means and the oil and protein in the two portions determined. His results on a sample of American white flint corn are as follows : Kernels less germs Germs. Percent 88.18 11.82 Per cent Oil 4 i . 57 32 . 83 " " Protein 4 13.09 19 .93 Lenz expressed the opinion that the small quantity of oil found in the kernel after the germ had been removed was really due to particles of the germ which had not been removed or to traces of oil deposited on the remainder of the kernel during the mechanical process of remov- ing the germ. This was further investigated by Atwater 5 who removed the germ together with a considerable portion of the kernel immediately sur- rounding the germ in order to insure the separation of all oil properly belonging to the germ. Following are his results : Outer portion Inner portion free from germ. including germ. Percent 76.43 23.57 Per cent. Oil 4 i .63 - Recently Voorhees 6 and Balland 7 have published the following re- sults : Glutenous layer Hulls. and starchy portion. Germs. 5.56 84.27 10.17 Voorhees. 12.40 74-iQ 13.50 Balland. 'This is given here as the sum of the zein, albumen, and casein reported by Salisbury. 2 By difference. 3 Allgemeine land- und forstwirtschaftliche Zeitung (1866) 257 ; Jahresbericht [Hoffmann] iiber die Agricultur-Chemie (1866) 9, 106. 4 In the dry matter. 5 Thesis, Yale College (1869) ; American Journal of Science and Arts (1869) [2] 48, 352. e New Jersey Agr. Exp. Station Bulletin (1894) 105. 7 Comptes rendus des Sct'ances (1896) 122, 1004. 140 BULLETIN NO. 53. The following table shows the composition 1 of the separate parts Carbohydrate Ash. Protein. Oil. Fiber. extract. 1.25 6.52 i-57 16.24 - 74.42 Voorhees. 1.44 8.20 J.33 ii .25 76.78 Balland. .68 12.15 I.-33 -65 84.99 Voorhees. .68 8-53 i. 08 .40 89.31 Balland. IO.02 ' 19-54 26.65 2.59 41 .20 Voorhees. 7.87 15.32 39-85 1.99 34-97 Balland. (dry). Hulls. Glutenous layer and starchy portion. Germs. These data confirm the earlier results, showing the germ, which constitutes only about 12 percent, of the kernel, to contain nearly twice as much mineral matter and three or four times as much oil as all of the remaining portions of the kernel. It is also rich in protein. Voorhees states that the portion richest in protein is the glutenous layer. In the manufacture of starch and glucose-sugar from corn these different portions of the kernel are separated much more perfectly than it is possible to do by hand although their original composition is some- what altered. Various methods 2 have been employed, but the following will indicate briefly a common process : The corn is steeped in warm water containing a little sulfurous acid and then reduced to a coarse powder. The germs together with a part of the hulls are recovered by floating and separated after drying. The material remaining in the water in suspension is passed through sieves arid the remainder of the hulls and some other coarse matter can thus be separated from the starch and the more finely divided gluten. The starch is finally allowed to settle and then the water containing the larger part of the gluten is run off. After further purification the starch is sold as such or is manufactured into other products, as glucose-sugar. The by-products, hulls, "gluten," and germs, separate or mixed, are sold as food stuffs, the larger part of the oil usually having been expressed from the germs. The mineral matter is, of course, largely removed from these products by the solvent action of the water. The analyses of corn oil cake was reported 3 by Moser as early as 1867 with the following results : Carbohydrate Ash. Protein. Fat. Fiber. extract. 8.07 I 7- I 9 ^2.58 11.41 5-75 The following is believed to fairly represent the composition (dry) of the several individual products, not as usually found on the market but in their purest condition : J As published Voorhees' results are evidently given on the basis of ash -free organic matter. They are here calculated to the basis of total dry matter. 2 Journal Society Chemical Industry (1887) 6, 84. 3 Jahresbericht (Hoffmann) iiber die Agricultur-Chemie (1867) 10, 259. Cf. ibid. (1872) 15, 21 ; (1874) 17, 15 ; (1876) 19, 15. }.] CHEMISTRY OK THE CORN KERNEL. 141 Carbohydrate Hulls' Ash. . . . . i . 02 Protein, ii. 18 Fat. 4- X 3 Fiber. 11.98 extract. 71 .60 Gluten 2 . . 1 . 14 44 .03 7.60 2 26 44 88 Germ cake 1 ..2. "58 27.2^ M. 84 7.41 47 . Q4 Starch 3 . . . .O. ^0 QQ.70 4 The correctness of Voorhees' statement that the portion of the corn kernel richest in protein is the glutenous layer is plainly apparent. Richards 5 has recently made proximate analyses to determine the heating value of the corn kernel. Calorimetric determinations were also made, being reported in terms of the British thermal unit 6 . Following are the results : Volatile Fixed Fuel Moisture. matter. carbon. Ash. value. Yellow dent 8.45 78.10 12.18 1.27 8202. White dent 8.88 77.22 12.90 i.oo 8338. EXPERIMENTAL. Ih the following work on the proximate composition of corn the total dry matter, the ash, the nitrogen, and the fat were determined directly. The protein was estimated by multiplying the total nitrogen by 6.25 and the carbohydrates by subtracting the sum of the ash, pro- tein, and fat from the total dry matter. In each single determination of the several constituents 2 gms. of air-dry substance were regularly taken. PREPARATION OF SAMPLE. All samples were air-dried, ground to pass through a sieve with circular perforations i millimeter in diameter, and then preserved in air-tight vessels, being thoroughly mixed just before being analyzed. DETERMINATION OF DRY MATTER. The air-dry substance was placed in a glass tube 10 cm. long and 2 cm. in diameter over one end of which a piece of hardened filter paper had been firmly tied with nickel wire, the tube with paper bottom having been dried and weighed in weighing tubes before being charged with the substance. The substance was dried with the tube lying in a horizontal position in a current of dry hydrogen at a temperature of 105, maintained by a boiling aqueous solution of glycerol in a double-wall bath provided with a return con- denser. The gas entered the bath at one end near the top and passed out at the bottom near the opposite end. 'N. J. Agr. Exp.. Station Bui. (1894) 105. 2 Conn. Agr. Exp. Station Report (1895)231. 3 Journal Society Chemical Industry (1887) 6, 84. "Starch. 5 U. S. Dept. of Agr., Exp. Station Bulletin (1898)49, 95. "Heat required to raise one pound of water from 50 to 51 F. 142 BULLETIN NO. 53. To determine the error in obtaining the weight of the empty tubes with the paper bottoms, 10 tubes were dried for one hour, cooled in desiccators and weighed in weighing tubes, then dried again for two hours and again weighed, with the following results : First weight. Second weight. i 47-7552 2 49-0332 3 46.1074 4 48 . 9842 5 48.6642 6 45-4501 7 4 8 -546i 8 47.8516 9 44-8934 10 46.2726 47-7550 49.0328 46. 1074 48.9843 48.6641 45.4500 48.5455 47.8518 44.8930 Decrease. .0002 .0004 .0000 .0001 .0001 .0001 .0006 .0002 .0004 .0001 46.2727 To determine the length of time required under the conditions mentioned to reduce the substance practically to a constant weight the following data were obtained, 2 gms. of air-dry substance being taken from 12 different samples : Weight of substance after drying 4 hours. Difference in weight between drying 4 or 8 8 or 16 hours. hours. .0120 .0039 .0117 0033 .0115 .0041 .0113 .0036 .0112 .0037 .0115 .0037 .0113 .0041 .OIIO .0038 .0113 .0045 .0114 -0035 .0118 .0048 .0106 .0039 16 hours. 1.7600 .7512 7413 .7489 .7513 .7483 7435 .7503 I .7387 1-7457 1.7411 After drying 4 hours the average decrease in weight for four hours more is 0.0114 gms. or 0.6 per cent, of the amount determined, and then for 8 hours more it is 0.0039 S ms - or - 2 P er cent, of the amount determined. This is a much narrower limit of error than can be main- tained in the determination of the constituent groups of the dry matter, and all dry matter determinations which follow were made by drying the substance 8 hours. It is noteworthy that during the second and third periods of drying all of the samples lost weight and in very nearly equal amounts, showing that for comparative results a very high degree of accuracy is attained. The following work was done to test the agreement of duplicate determinations on the same sample. Twelve different samples were selected, and the 24 portions of 2 gms. each were all dried together: i8 9 8.] CHEMISTRY OF THE CORN KERNEL. Weight of dry matter. Variation. i . . . . 1.8276 1.8273 .0003 2 . . . . i .8230 1.8238 .0008 3-- ..1.8218 i .8222 .0004 4-- ..1.8319 1.8314 .0005 5-- . . i .8244 i .8249 .0005 6.. ..1.8198 i .8194 .0004 7-- . .1.8264 1.8267 .0003 Weight of dry matter. . i .8240 .1.8243 . i .8202 .1.8176 . 1.8150 i 8242 i .8240 i . 8209 i. 8186 1-8155 Variation. .0002 .0003 .0007 .0010 .0005 Average 0005 From these results and those preceding it is seen that determina- tions made in the same bath and at the same time show a remarkable degree of accuracy when compared only with themselves, and among themselves they are strictly comparable. To determine the variation which might be caused by unavoidable differences in temperature, hydrogen current, etc., the following 36 duplicate determinations of dry matter were made, in every case the duplicate determinations being made at different times, /. 45 11.49 11.48 4.26 4-25 82.80 82.79 49J 1.42 1.42 8.36 8-43 4.87 4-94 85.35 85.21 32-j; : g 11.78 11.77 4-84 4.82 82.00 82.01 50-j 1.65 1.65 12.28 12.28 4.76 4-75 81.31 81.32 It must be admitted that these results are far from being uniform. Indeed, they are quite the opposite, and seem to bring out and clearly to establish the fact that there are extreme variations in the chemical composition of corn grown from the purest seed of a single variety and under markedly uniform field conditions. Then the results given in the experiment preceding this are to be considered merely as averages from a large number of small samples of widely varying composition. 152 BULLETIN NO. 53. \_J li ty> Following are the maxima and minima of all constituents as shown by the 50 duplicate analyses : Ash. Protein. Fat. Carbohydrates. Maximum 1.74 13.88 6.02 85.79 Minimum 1.09 8.35 3-95 78.92 Difference ..0.65 5-53 2.07 6.87 With every constituent the variation is greater than Flechig found; with 13 different varieties, and it is nearly as great as found by the Con- necticut Experiment Station with about 75 different varieties of corn grown under 90 presumably different conditions. This comparison is facilitated by the following table which gives the number ot samples containing the different constituents in amounts above and below certain specified percentages; columns I. and II. give the numbers of such samples 1 from my results and those of the Con- necticut Station, respectively: Percent. I II Percent. I. II. Ash above 1.70 i 5 below i.io i 9 Protein " 13.75 x 3 " 9.00 2 4 Fat " 6.00 i i " 4.00 i 2 Carbohyrates " 85.00 5 3 " 79.00 i 4 It is observed that the number of samples with percentages of ash outside of these extremes is 2 with my results and 14 with the Connecti- cut experiments. This is in accord with the well known fact that the amount of ash constituents taken up by plants varies largely with the amount of soluble mineral matter in the soil, somewhat regardless of the needs of the plant; and it indicates wide variations in Connecticut soils in this regard, as we should expect to be the case. By reference to page 138 it is seen that the percentages of ash in the 90 samples varied from 0.91 to 2. 10. If we omit the ash, the number of percentages of all constituents which fall outside the limits given above is n with my results from 50 samples and 16 with the Connecticut results from 90 samples. ANALYSES OF PARTS OF THE EAR. In studying this question 30 dupli- cate analyses were first made on different parts of ears. Five ears were divided lengthwise into 3 samples each in the following manner: If the ear were i2-rowed, 3 samples of 4 consecutive rows each were made; if i6-rowed, 3 samples of 5 consecutive rows each were made, one row being left, etc., etc. Duplicate analyses of 15 samples thus prepared from 5 different ears gave the following results. The different ears are distinguished by the letters (a), (b), (c), (d), and (e): 1 Not single determinations. 1898.] CHEMISTRY OF THE CORN KERNEL. '53 8(c)j Ash. Protein. Fat. Carbohy- drates. Ash. Protein. Fat. Carbohy- drates. 1.42 i-43 10.79 10.75 4-57 4.58 83.22 83.24 'w\i$ 10. 15 10.20 5.20 5-i7 83.29 83.26 1.48 1-47 10.97 10.94 4-54 4-51 83.01 83.08 io(d)|;;39 10.46 10.46 4.28 4.29 83.87 83.87 1.50 1.51 10.66 10.72 4-53 4-55 83-31 83.22 n(d)-j'-43 1 i .42 10.25 10.27 4.22 4.20 84. 10 84.11 i.5i i-52 12. OO 11.98 4.60 4-59 81.89 81.91 i2(d)^-43 I I -45 10.09 10.06 4.16 4-15 84.32 84-34 1.49 1.48 12. OI I2.O5 4-57 4-57 8i.93 81 .90 {e * J 1-34 M-36 11.19 II .20 4.80 4.78 82.67 82.66 1.48 1-47 12. ig 12. 08 4.85 4.80 81.48 81.65 / \ i I -3 14 (e) { 1.28 10.66 10.62 4.91 4-89 83-13 83.21 i-37 1-37 lO.Og IO.IO 5-24 83.30 83-36 , (e} \ 1.36 (e) } 1.36 10.81 10.92 4-83 4-79 83.00 82.93 i .31 1-34 10.14 10.18 5.08 83.47 83-30 These results indicate uniformity in the composition of the different parts of the ear. The following shows the greatest total variation in the 6 single determinations of each constituent in any one ear; and also the total variation between the different ears: Ash. Protein. Fat. Carbohydrates. In any single ear 09 .58 .28 .55 In five ears 24 2.13 1.09 2.86 Another lot of five ears was selected and each of these was divided crosswise into 3 samples of approximately equal amounts, which for convenience are designated "tip," "middle," and "butt," the ears being lettered (f), (g), (h), (i), and (j). The duplicate analyses follow: / ish. Carbohy- Carbohy Protein. Fat. drates. Ash. Protein. Fat. drates. 16 (f) I Tip '/ .58 59 11.78 5.09 81.55 24 (h) j .51 10.49 4.01 83.99 11.76 5.10 81.55 Butt | .49 10.46 4.00 84.05 17 (f) I Middle ( 58 57 12.22 5.13 81.07 25 (i) j .47 10.58 4.58 83.37 12.26 5.03 81.14 Tip / .48 10.61 4.60 83.31 18 (f) j Butt ) 56 .58 12.36 5.04 81.04 26 (i) \ .45 11.05 4-56 82.96 12.42 5.03 80.97 Middle / .44 11.03 4.60 82.93 19 (g) \ > Tip 1 i 49 49 11.99 4.86 81.66 27 (i) \ 1.47 11.03 4-48 83.02 11.97 4-84 81.70 Butt M.48 10.96 4.46 83.10 20 (g) \ Middle ( 1.51 [.51 12.49 4.77 81.23 28 (j) j .77 10.87 4-36 83.00 12 49 4.76 81.24 Tip j .74 10.78 4.37 83.11 21 (g) I Butt j [ -5 i-5i 13.02 4.57 80.91 29 (j) \ .65 11.35 4-56 82.44 13.10 4.59 80.80 Middle ( .62 11.31 4.58 82 49 22 (h) j] Tip j i 37 35 9.72 3.90 85.01 30 (j) \ .71 11.32 4-28 82.69 9-67 3.93 85.05 Butt ( .72 11.28 4.29 82.71 23 (h) ( Middle 1 i-37 1-35 10.07 3-98 84.58 10.08 3-97 84.60 154 BULLETIN NO. 53. These results are similar to those in the preceding experiment. The following shows the total variation: Ash. Protein. Fat. Carbohydrates. In any single ear ........... 16 1.13 .30 1.06 In five ears ................ 42 3-43 i .23 4.25 It is observed that in every case the tip is lowest in protein and that usually the middle is lower than the butt, the average total difference in the ear being 0.73 per cent, and the widest 1.13 per cent, as shown above 1 . The variation in ash and fat is small and shows no such pecu- liarity. The carbohydrates, being estimated by difference, appear, of course, as the complement to the sum of the other substances and show in the opposite direction approximately the variation of the most variable determinable constituent. PARTIAL ANALYSES OF SINGLE KERNELS. From 1009 separate deter- minations Richardson' 4 has found the average weight of 100 kernels of air-dry corn to be 36.7 gms. Allowing 10 per cent, for moisture, gives 0.330 gms. as the average weight of the dry kernel. This weight is too small for a very exact single determination of a single constituent, and, of course, no attempt has been made to do more than that. The ash determination was made by incinerating the whole kernel without grinding, the weight of the dry matter having been previously taken after drying the kernel for 8 hours in a current of hydrogen at 105; and the nitrogen determination was made on the whole kernel after drying and without grinding, the digestion proceeding as satisfac- torily as with ground corn. No satisfactory method was found for the determination of the fat in a single kernel. The ash determinations in 10 single kernels taken from as many different places on an ear gave the following results : Kernel, Ash, Ash, Kernel, Ash, Ash, weight. weight. per cent. weight. weight. per cent. I. . ...0.3579 o . 0048 1-34 6. 0.3953 0.0053 1-34 2. . ...0.2947 0.0042 1-43 7- 0.4507 o . 0066 i .46 3-- ...0.3985 0.0052 1.30 8. 0.4589 o . 0064 1-39 4-- ...0.3585 o . 0046 1.28 9- . . . .0.4211 0.0062 i-47 5-. -0.3936 o . 0054 1-37 10. . . . .0.5072 o . 0070 I-3S For further work on the ash content several ears of corn were selected, and from each a sample of corn, consisting of a number of rows and believed to fairly represent the ear, was taken and its percent- age of ash in the dry matter determined. Then for the special investiga- tion of the ash content of single kernels four ears from the lot were chosen, of which two were high and two were low, comparatively, in the 'It will be seen that later work on single kernels tends to confirm and establish this as a characteristic of the ear of corn. 2 U. S. Dept. of Agr., Div. of Chem Bui. (1884) 4, 82. i8 9 8.] CHEMISTRY OF THE CORN KERNEL. '55 percentage of ash as previously determined. From each ear 10 kernels were selected at approximately equal distances apart throughout the length of the ear, the kernels being numbered from i to 10 and the order running from tip to butt. The data from the ash determinations in the single kernels and also the percentage of ash in the large sample from the same ear are given below : Ear No. i. Ash = i .73 per cent. Ear No. 2. Ash = 1.65 per cent. Kernel, Ash, Ash, Kernel, Ash, Ash, weight. weight. per cent. weight. weight. per cent. I -O.3334 0.0050 i .50 i 0.2933 0.0048 i .64 2 . o, 3367 o . oo 5 3 i .57 2 O 27Q7 o . 0046 M. . v*f I 64 3 . . . .0.3662 j j o . 0059 1.61 3 0.2945 o . 0048 * V*f 1.63 4 . . . .0.3901 0.006 i 1.56 o 2551 0.0042 5 . . . .0.3417 O .OO')7 . j v i .67 0.3207 0.0051 I .jg 6 . o 3614 J 1 o . 006 i i .60 6 O 3OOS I 63 7. . . . 0.3798 0.0065 * . **y I.7I 7 0.3346 o . 0056 * ^ J 1.68 8 . .0.4030 o . 0066 I .64 8 O 3144 0.0052 i 65 g . .0.4446 O.OO73 "f I .64 q o. 3463 0.0059 j i .70 / J o . 007 i . .f 1.74 IO o. 1627 0.00^8 / i ,60 Ear No. 3. Ash = i . 10 / T percent. Ear No. 4. Ash = i.n percent. Kernel, Ash, Ash, Kernel, Ash, Ash, weight. weight. per cent. weight. weight. per cent. i . .0. 2630 0.0029 I . IO - o 3080 0.0035 I 14 2 . . . .0. 2591 0.0028 i. 08 2 O 34QQ O OO43 x * L 'r 3- ....0.2655 o . 0029 1.09 3-. *_* . W*f J 0.0038 I.I3 4- 0.2887 0.0031 I . IO 4-- . . .0.3422 o . 0040 17 5- 0.3077 0.0033 1.07 5-- ...0.3970 O.OO45 13 6. . . . .0.3216 0.0035 1.09 6.. ...0.3514 0.0043 .22 7- 0.3363 o . 0036 1.07 ? ...0.3767 o . 0047 25 8. 0.3476 0.0038 I .10 8.. . . .0.4186 0.0050 .19 9- 0.3467 0.0042 I .21 9-. ...0.4331 o . 0048 .11 10. . . . .0.4042 0.0045 I . II IO. . . . .0.4638 0.0051 .IO These results confirm those of the previous experiments in indicat- ing uniformity in the composition of the ear in all parts, although slight variations are found, of course. It may be noted, however, that the variation from the average percentage is rarely equivalent to more than three-tenths of a milligramme in the weight of the ash. In the work on the protein content of single kernels, 5 ears, 3 of which were high and two relatively low, in protein were selected from a number of ears in a manner analogous to that described in the previous experiment. As duplicate determinations were not made with single kernels the complete analytical data of this work are reported. The water used in making up reagents and standard hydrochloric acid and in the analytical process where needed had been twice distilled, once with sulfuric acid, to free it from ammonia, and once with calcium 156 BULLETIN NO. 53. hydroxid to remove carbon dioxid and volatile acids. In standardizing the hydrochloric acid and ammonia solutions the same automatic pipette and burette were employed as in the subsequent analyses 1 . The hydrochloric acid was standardized by means of silver nitrate, a method whose details I have previously investigated 2 and found to be exceed- ingly accurate. Lacmoid indicator was used in standardizing the am- monia, and chemically pure cane sugar was employed in making "blank" determinations to find the "correction" for reagents. Follow- ing are these data : Standardizing hydrochloric acid. 35 cc. 3 HC1 gave 1.4103 and 1.4104 gms. AgCl. Standardizing ammonia. 17.5 cc. HC1 required 27.55 and 27.55 cc. NH 3 . Blank determinations with sugar. 17.5 cc. of standard hydrochloric acid were taken and to neutralize the excess of acid required 27.47, 27.45, and 27. 47 cc. of standard ammonia solution. The atomic weights 4 used are : Cl = 35.453; Ag = 107.938; N = 14.041. The factor, 6.25, was used to obtain the protein equivalent. These data give 194933 as the logarithm (mantissa) for the weight of protein equivalent to one cubic centimeter of standard ammonia. In the following work 17.5 cc. of standard hydrochloric acid were taken in each determination, and the volume of standard ammonia re- quired to neutralize the excess of acid is given in the tables in cubic centimeters : Ear No. i. Protein = 13.06 per cent. Ear No. 2. Protein = 13.87 percent. Kernel, Ammonia to Protein, Kernel, Ammonia to Protein, weight. neutralize. per cent. weight, neutralize, per cent. 1 ....0.2945 25.12 12.46 i ....0.3206 24.97 12.17 2 ....0.3127 24.96 !2.54 2 ....0.3207 24.81 12.94 3 0.2893 25.16 12.44 3 0.3094 24.99 12.51 4 0.2991 25.07 12.50 4 ...0.2841 24.97 I3-4 2 5 ....0.3147 24.99 12.30 5 0.3475 2 4-55 13-12 6 0.3162 24.94 12.49 6 0.2899 24.76 14-59 7 0.3544 2 4- 6 3 12.50 7 0.2835 25.07 13.21 8 0.3302 24.90 12.14 8 0.3475 24.48 13-43 9 0.3601 24.67 12.14 9 0.3179 24.79 13-16 10 0.3368 24.73 12.71 10 0.3301 24.50 14-05 x lf this precaution is observed, if the full measure of acid is always taken, and if the graduation of the automatic ammonia burette is strictly uniform, there is no special necessity for the apparatus to read absolute values. 2 Methods of Standardizing Reagents. Master of Science Thesis, Cornell Uni- versity, 1894. 3 Twice the volume of the automatic pipette. ^Ostwald, Grundriss der allgemeinen Chemie (1890) 31. i8 9 8.] CHEMISTRY OF THE CORN KERNEL. 157 Ear No. 3. Kernel, weight. I o 3626 2 0.3039 3 o. 3353 4 o. 3048 5-- ..0.3225 6 o. 3013 7 . . .0.2635 8 0.3204 9 0.3254 10 O. 3IQ 1 ; Kernel, weight. i. . . . .0.2819 2. . . ..0.2682 3-. . . .0.2378 4.. . . .0.2641 5-- . . .0.2891 Protein = 12, ,96 percent. Ear No. 4. Protein = 7.59 per cent. Ammonia to neutralize. Protein, per cent. Kernel. Ammonia to weight. neutralize. Protein per cent. 24.79 "53 i ....0.2503 26.27 7-45 25.07 12.32 2. .. .0.2432 26.29 7-54 24-85 12.19 3- ... .0 2383 26.29 7.69 25.02 12.54 4. . . . .0.2118 26.45 7-47 24.96 12. 14 5- . .O 2752 26.10 7-74 24-97 12-95 6 . . O 27IQ 25.95 8.70 25-30 12.84 7 . . . .0.2758 25-97 8.46 Lost by accident. g . .O 27O3 8 60 24.96 I2.O4 9 . . . ,o 2809 8 8 86 24.86 12.75 10 8 8. 10 Ear No. 5 Protein 8.40 per cent Ammonia to Protein Kernel, Ammonia to Protein neutralize. per cent. weight. neutralize per cent. 26.07 7.72 6 ... .0. 3002 2"? 78 8.76 26.02 8.41 7 . O.273O * j /* 25 QI 8.89 26. 19 8.37 8 . . . .0.2830 * j y * 2"5.83 902 26.06 8.31 9 . . . .0.2973 j - j 25.76 . w* 8.96 25-98 8.02 . . . .0.2821 25.86 ^ -yv 8.89 The concordant evidence of 30 duplicate analyses of parts of ars, of 50 ash determinations, and of 50 protein determinations in single kernels would seem to warrant the conclusion and to establish the fact that the composition of the ear is approximately uniform throughout. Extended investigations, based upon the facts brought out in these studies of the proximate composition of corn, are being continued by the writer. PART II. THE COMPLETE COMPOSITION OF CORN. HISTORICAL. THE ASH OF THE CORN KERNEL. The earliest analysis on record of the ash of corn is evidently that made by De Saussure 1 reported in 1804. Following are his results: Potash 14 . oo Phosphate of potash 47 . 50 Chlorid of potash 0.25 Sulf ate of potash 0.25 Earthy phosphates 36 . oo Silica > i . oo Metallic oxids o. 12 Loss.. 0.88 Researches Chimiques sur la Vegetation, by Theod. De Saussure (1804) 351; Trans. N. Y. State Agr. Soc. (1848) 8, 727. 158 BULLETIN NO. 53. \_July, Subsequently Letellier 1 reported the following analysis: Magnesia 17.00 Lime 1.30 Phosphoric acid 50 . 10 Silica 0.80 Sulf uric acid Trace Potash, soda, and loss 30.80 As the later investigations will show, the analysis of Letellier gives very approximately the true composition of corn ash. Much less approximate are the analyses of Salisbury, of which he reported 2 several similar to the following: Silica 1.45 2 . 65 SO 3 0.21 0.13 P 2 5 ? 50.96 49-31 Iron phosphate 4-35 o . 75 Lime.... -i5 -45 Magnesia .-, . . 16.52 15. 49 Potash 8.29 5.19 Soda 10.91 19.18 NaCl 0.25 0.90 Cl o. 10 Organic acids 3.10 3.45 Coal 1.75 Later analyses by Liebig and Kopp 3 , Stepf 4 , Way and Ogston''', and Bibra 6 gave the following results: Liebig Way and and Kopp. Stepf. Ogston. Bibra. Bibra. K 2 30.74 28.80 28.37 24.33 26.75 Na 2 O 3.50 1.74 1.50 3.85 MgO 14.72 J 4-90 13.60 16.00 J5-24 CaO 3.06 6.32 0.57 3.16 2.56 Fe 2 O 3 0.84 i.si 7 0.47 i.88 8 2.00" P 2 s 44-50 44.97 53.69 49.36 47.47 SO 3 4.13 Trace. i.oo 1.20 SiO 2 1.78 1.55 2.77 1.93 Cl 0.50 .... In 1880 Wolff 9 gave the following as the average of 15 analyses of the ash of corn: 1 Annalen der Chemie und Pharmacie (1844) 50, 403. 2 Trans. N. Y. State Agr. Soc. (1848) 8, 678. 3 Jahresbericht iiber die Fortschritte der Chemie (1856) 815. 4 Journal fiir praktische Chemie (1859) 76, 88. 5 Liebig's die Chemie in ihre Anwendung auf Agricultur (1865) 1, 384. "Same reference. 7 And SO 3 and loss. "And loss. "Wolff's Aschen Analysen (1880); Thorp's Dictionary of Applied Chemistry (1890) 1, 497. 1898.] CHEMISTRY OF THE CORN KERNEL. 159 K 2 O. Na.jO. MgO. CaO. Fe 2 O 3 . P 2 O 5 SO 3 SiO 2 Cl. 29.8 I.I 15.5 2.2 0.8 45-6 O.8 2.1 O.Q Quite recently Scovell and Peter have reported 1 a somewhat extended investigation of the ash of corn with reference to its content of fertil- izing elements. Following are the percentages of potassium oxid and phosphoric oxid in the pure ash as found in 8 samples: K 2 0. P Z B . K 2 0. P,0 5 . 28.38 48.52^ 29.66 52.14 28.98 51.85 29.95 53-03 29.41 52.45 29.27 53.10 29.38 52.75 28.18 51.42 It seems evident that as a rule the ash of corn contains at least 95 per cent, of the phosphates of potassium and magnesium, about twice as much potash as magnesia being present. THE PROTEIDS OF THE CORN KERNEL. Zein, the most important proteid in corn was discovered and named by Gorham in 1821 (see page 130), although he concluded from his investigations that it was not a nitrogenous body. The zein was obtained by extracting with alcohol the residue of powdered corn insoluble in water, 3.30 per cent, of zein being found. By subsequent extraction of the corn with dilute acid and alkali 2.75 per cent, of what was thought to be albumen were obtained. Soon after the publication of Gorham's work Bizio 2 reported an in- vestigation of corn in which he claimed to have discovered the alcohol soluble proteid, and, curiously enough, he states that he had named it zein, from the Greek word meaning "nourishing substance" because of the fact that it was a nitrogenous body. He points out several differences between his zein and that which Gorham had found, and mentions especially that in 1820 Configliachi :i had obtained ammonia from zein by dry distillation. By means of ether Bizio extracted oil from zein and then found that the residue was but partially soluble in alcohol. These two portions, the one soluble and the other insoluble in alcohol, he thought to be two different substances and to be identical with the gliadin and zymom which Taddei 4 had found in the gluten of wheat. He gives the alcoholic extract the following composition: Oil, soluble in ether 20.0 per cent. Gliadin, soluble in alcohol 43-4 Zymom, insoluble in alcohol 36.6 " Kentucky Agr. Exp. Station Report (1891) 16. -Journal fur Chemie und Physik (1823) 37, 377. 3 Ibid. (1823) 37, 383. J Ibid. (1820) 29, 514. l6o BULLETIN NO. 53. \_J u tyi Salisbury 1 obtained "albumen" from corn by extracting with water and coagulating by heat, and " casein " from the filtrate by precipitating with acetic acid. He extracted zein and oil by means of alcohol and separated them by evaporating the alcohol and extracting the oil with ether. Evidently because Berzelius 2 in commenting on Gorham's results, had expressed the opinion that the zein of corn and the gluten of wheat were identical, Stepf 3 assumed and stated incorrectly that Gorham claimed to have obtained zein by kneading corn meal with water, in the same manner as gluten may be obtained from wheat; and he tried repeatedly but in vain to accomplish such result. By extracting corn with alcohol and purifying the extract by treating it with water and with ether to remove sugar and oil, he states that he obtained pure zein very similar to that obtained by Gorham. It was easily soluble in alcohol, but by repeated solution and evaporation of the alcohol the zein was partially changed into a modification insoluble in alcohol. Stepf called the two modifications plant glue ( Pflanzenleim} and plant casein, sub- stances already known. Albumen was also obtained from an aqueous extract of corn by coagulating with heat. The dry matter of corn was found to contain 0.7 per cent, of albumen and 7.5 per cent, of zein. Stepf further states that from four closely agreeing determinations he found pure zein to contain 15.6 per cent, of nitrogen. In 1869 Ritthausen reported 4 an investigation of the proteids of the corn kernel. Misled by Stepf's erroneous assumption, Ritthausen vainly endeavored to obtain a cohering glutenous mass by kneading corn meal with water. Zein was obtained to the amount of 5 per cent, by extracting powdered corn with alcohol and (A) by evaporating the alcohol and extracting the residue with ether, or (B) by precipitating the zein in the alcoholic extract by the addition of much ether. Zein was further puri- fied (C) by repeated treatment with alcohol and ether, and (D) by dis- solving in o. i to o. 15 per cent, potassium hydroxid solution, precipitating with dilute acetic acid, redissolving completely 5 in alcohol, and precipitating with much water. iTrans. N. Y. State Agr. Soc. (1848) 8, 727. 2 Jahresbericht iiber die Fortschritte der physischen Wissenschaften (1823) 2, 124. 3 Journal fiir praktische Chemie (1859) 76, 88. Journal fur praktische Chemie (1869) 106, 471. 5 Ritthausen points out that this action shows zein to not consist in part of casein, which would have formed an " alkali albuminate " insoluble in alcohol. i8 9 8.] CHEMISTRY OF THE CORN KERNEL. 161 Ultimate organic analyses of these four preparations gave the following results: Carbon . . . Hydrogen Nitrogen . Sulfur Oxygen. . . A. 54.66 7-45 15-50 0.69 21.70 B. 54-7 1 7-50 15-53 22. l6 2 C. 54.76 7-57 15-45 22.22 D. 54.66 7-51 15-85 0.65 21-33 Average. 54.69 7-51 15-58 0.69' 21-53 The fact may be noted that these results were not corrected for the ash content of the zein, which it is stated was insignificant; and also the more important fact that the nitrogen determinations of both Stepf and Ritthausen were made by the method of Varrentrap and Will 3 employing the old atomic weights of platinum (197.2) and nitrogen (14). I have recalculated their results using the revised atomic weights (Pt 194.8; N=i4.o4i) 4 and find Stepf's average of four determinations to be 15.84 per cent, nitrogen and the average of Ritthausen's results 5 to be 15.82 per cent, nitrogen, in zein, while preparation (D) alone gives 16. 10 per cent, nitrogen. By repeated solution in alcohol and evaporation of the solvent, Ritthausen obtained zein which was insoluble in alcohol "dilute or strong, warm or cold." He states positively that zein (or Maisfibrin, as he prefers to call it) is not a mixture of proteid bodies but a single homogeneous substance. After the alcoholic extraction of the corn was complete, the residue was extracted with 0.25 per cent, potassium hydroxid solution, and the extracted proteids precipitated by acetic acid. About 0.5 per cent, of substance was thus obtained from corn, which Ritthausen has since referred 6 to as globulin. He gives the following as the composition of the ash-free substance: Carbon 51.41 Hydrogen 7 . 19 Nitrogen 17.72 Oxygen and Sulfur 23 . 68 1 Sulfur determination in (D) was not considered trustworthy. 2 Should be 22.26 evidently. 3 Annalen der Chemie und Pharmacie (1841) 39, 257. 4 Ostwald, Grundriss der allgemeinen Chemie (1890) 31. I have checked this recalculation from the weight of zein employed and of platinum found as reported in Ritthausen's analytical data, and find that he used atomic weights as stated above. 6 Landwirtschaftliche Versuchs-Stationen (1896) 47, 391. 1 62 BULLETIN NO. 53 \_Juty, In 1877 Weyl 1 pointed out that a 10 per cent, solution of sodium chlorid extracted from the powdered corn kernel a globulin proteid which coagulates at 75. The corn proteids soluble in sodium chlorid solution have been very thoroughly investigated by Chittenden and Osborne 2 and the pre- vious work on zein, the alcohol-soluble proteid, was carefully repeated. With 10 per cent, sodium chlorid solution they extracted from powdered corn about 0.5 per cent, of proteid matter from which they were able to separate at least four different bodies now known 3 as (i) proteose, (2) very soluble globulin, (3; maysin (globulin), and (4) edestin (globulin). As the salt is removed from the solution by dialysis, the maysin and edestin precipitate, the other bodies remaining in solution. By long continued dialysis a part of the very soluble globulin is pre- cipitated, the remainder (originally thought to be albumen by Chitten- den and Osborne) being precipitated by hydrochloric acid. Of the proteose, a part (also first called albumen) was obtained by coagulating with heat, and the remainder was precipitated with alcohol. After re- dissolving in salt solution the mixture of the two precipitated globulins, maysin was separated from edestin by coagulating with heat, the edestin being finally precipitated as the salt was removed by dialysis. Other methods were also employed to separate these two globulins, based upon the fact that maysin is readily soluble in extremely dilute salt solutions, while edestin requires greater concentration of salt for solution. The averages of all analyses of each of these four proteids follow: Very soluble Proteose. globulin. Maysin. Edestin. Carbon 51.30 52.84 52.68 51.71 Hydrogen . . 6.71 6.82 7.02 6.85 Nitrogen 16.35 !5-38 16.78 18.12 Sulfur ,. 2.00 1.37 1.30 o'86 Oxygen 23.64 23.59 22.22 22.46 The different preparations of proteose and of the very soluble globulin show some wide differences in composition which, it is believed, are "simply due to their alteration by the process made use of" in their separation. It was found "that these soluble bodies are exceedingly prone to change." By the long continued action of water and salt solutions an insoluble modification of variable composition was pro- duced from maysin and the very soluble globulin. ^eitschrift fur physiologische Chemie (1877) 1, 84. 2 American Chemical Journal (1891) 13, 453, 529; (1892) 14, 20. 3 Osborne, Conn. Agr. Exp. Station Report (1896) 20, 391. To avoid confusion these terms are here used instead of myosin, vitellin, etc. 1898.] CHEMISTRY OF THE CORN KERNEL. 163 Following are the maxima and minima of the several constituents determined in all analyses of proteose, very soluble globulin, and the insoluble modification : Very soluble Insoluble Proteose. globulin. modification. Carbon 52.061050.07 53.531052.36 53.95*051.97 Hydrogen 6.91 " 6.54 6.90 " 6.74 7.05 " 6.90 Nitrogen 17.28 "15.78 15.69 "15.16 16.82 "15.87 Sulfur 2.37 " 1.62 1.48 " 1.26 1.16 " 1. 12 The several analyses of both maysin and edestin agree within nar- row limits. After the extraction with salt-solution was completed, zein, the most abundant proteid in the corn kernel, was obtained by extracting with 75 per cent, alcohol "at about 50, and highly purified by repeated solution in alcohol and precipitation with water, the last traces of oil being removed by final extraction with ether* By warming with water or very dilute alcohol zein was readily changed into the insoluble modification. Following is the composition of zein as shown by the averages of several closely agreeing analyses of both the soluble and the insoluble modifications: Soluble zein. Insoluble zein. Carbon 55-28 55 .15 Hydrogen 7.27 7 24 Nitrogen 16 . 09 16.22 Sulfur 0.59 062 Oxygen 20 . 77 20 . 77 The statement is made that "corn meal, after thorough extraction with "salt solution and warm dilute alcohol, yields little proteid matter to dilute solutions of potassium hydroxid (0.2 per cent.)." Osborne's more recent investigations 1 have shown this assumption to be very erroneous; and he now estimates such treatment to yield 3.15 percent, of proteid soluble in 0.2 per cent, potassium hydroxid solution. It is noteworthy that this quantity is seven times the total amount of the several proteids extracted by salt-solution. Analyses of the purified preparation gave the following results : Carbon 51.26 Hydrogen 6.72 Nitrogen 15 . 82 Sulfur o . 90 Oxygen 25 . 30 J Conn. Agr. Exp. Station Report (1896) 20, 391. 164 BULLETIN NO. 53. [/ufy, The quantities of the different proteids in the corn kernel are esti- mated as follows : 1. Proteose, soluble in pure water 0.06 per cent. 2. Very soluble globulin 0.04 " " 3. Maysin, soluble in extremely dilute salt-solutions 0.25 " " 4. Edestin, soluble in more concentrated salt-solutions. . .o. 10 " " 5. Zein, soluble in alcohol 5 . oo " " 6. Proteid matter, soluble in dilute alkalies 3 .15 " " 7. Proteid matter 1 insoluble in any of these solvents . . . .1 .03 " " Osborne has calculated the mean percentage of nitrogen in corn proteids to be 16.057. In a review of the percentages of nitrogen in the proteids of various vegetable substances, Ritthausen 2 places corn in the class with proteids containing 16.67 P er cent, of nitrogen, and uses the factor 6.00 for cal- culating protein from the percentage of total nitrogen. It is observed, however, that Ritthausen has misquoted his own results on the composi- tion of zein, as will be seen from the following : Original 3 . As quoted. Carbon 54 .-69 54 . 69 Hydrogen 7.51 7 5 Nitrogen 15.58 16.33 Sulfur 0.69 0.69 Oxygen 21.53 21.53 An error of 0.05 appears in the hydrogen and of 0.75 in the nitro- gen, and furthermore the total is 100.80, clearly showing that the analysis is misquoted. His analysis of globulin is quoted correctly. In this connection it is interesting to note that, if we take Ritt- hausen's determinations of zein (containing 15.58 per cent, of nitrogen) as 5.00 per cent, of the corn, and globulin (containing 17.72 per cent, of nitrogen) as 0.50 per cent, of the corn, and recalculate the nitrogen according to the revised atomic weights of platinum and nitrogen, which show zein to contain 15.82 per cent, and globulin 17.99 per cent, of nitrogen, we then find the mean percentage of nitrogen in the pro- teids to be 16.02, which is practically identical with Osborne's result, and proves conclusively that with our present knowledge we are to use 6.25 as the factor for estimating protein from the total nitrogen content of corn. THE CARBOHYDRATES OF CORN. Gorham and Bizio, to whose work reference has already been made, separated sugar, gum, fiber, and Nitrogen in residue from 100 parts of corn multiplied by the factor 6.25. 2 Landwirtschaftliche Versuchs-Stationen (1896) 47, 391. 3 Journal fiir praktische Chemie (1869) 106, 483. 1898.] CHEMISTRY OF THE CORN KERNEL. 165 starch in the carbohydrate group, with the following results, the starch being estimated by difference : Carbohydrates. Gotham. Bizio. Sugar 1.59 0.90 Gum 1.92 2.29 Fiber 3.30 7.71 Starch 84.60 80.91 In connection with his researches upon the starch content of many vegetable substances including corn, Krocker 1 showed the absence of appreciable amounts of sugar or dextrine in the ripe seeds of cereals. Mitscherlich is quoted as having reached the same conclusion. Krocker's method for determining starch was by hydrolysis and fer- mentation, the amount of starch being calculated from the weight of carbon dioxid liberated. In modern chemistry the relations are ex- pressed by the following equations, in which the starch first takes up water and is converted into glucose-sugar by the catalytic action of acids: C 6 H 10 5 +H 2 0=C 6 H 12 6 and then the sugar is decomposed into alcohol and carbon dioxid by yeast, C 6 H 12 O 6 =2C 2 H 5 OH-f2CO,. In case a measurable quantity of hexose-sugars were present it was determined by fermentation previous to the hydrolysis of the starch. Duplicate determinations on a sample of corn containing 14.96 per cent, of water gave the following results: Corn taken 3.35 2.98 gms. Carbon dioxid found 1.02 0.92 " Starch equivalent 1.877 1.693 " Starch in dry matter 65.88 66.80 percent. Aside from the determination of fiber as commonly made and reported in proximate analyses and Atwater's estimation of sugar (see page 134), nothing further of importance concerning the chemical composition of the carbohydrates of corn is found until 1887, when Archbold 2 gives the following percentages of different carbohydrates in corn, as representing "the average of many samples analyzed in the course of one year's working " in a large starch factory: Water 1 1 . 20 Dry Starch 54 .80 61.71 Cellulose . 16.40 18.47 Gum and sugar 2.90 3.27 1 Annalen der Chemie und Pharmacie (1846) 58, 212. -Journal Society Chemical Industry (1887) 6, 84 1 66 BULLETIN NO. 53. Archbold's report shows 1 that 55.6 per cent, of starch are actually obtained from corn (dry basis) in the commercial process of starch manufacture, and that several different by-products still contain traces of starch. In 1889 Washburn 2 reported an investigation of the cane sugar con- tent of corn. By extracting 1400 gms. of ordinary field corn, to which 3 gms. of magnesia had been added to prevent possible inversion of sugar, with 72 per cent, alcohol, shaking the solution with ether to separate fat, and purifying the sucrose in the filtered aqueous layer by repeated precipitation as strontium sucrate and decomposition of the precipitate by carbon dioxid (method of Schultze 3 ), 1.105 g ms - ot pure cane sugar were obtained by crystallization. American sweet corn yielded larger amounts, 10.5 gms. of sugar being obtained from 2000 gms. of corn. Washburn states that all of the sugar in the co"rn is not obtained by this process. Marcacci 4 has found over i per cent, of sugar in corn. Pentosans (C 5 H 8 O 4 ), which are also termed wood gum and hemi- cellulose, were found in corn by Stone 5 . These carbohydrate bodies 6 yield pentoses (C 5 H 10 O 5 ), also called penta-glucoses, by hydrolysis with dilute acids (C 5 H g O 4 +H 2 O = C 5 H 10 O 6 ), and furfurol (C^O,) by dis- tillation with moderately concentrated acids (C 5 H ao O r) 3H 2 O = C 5 H 4 O 2 ), reactions which serve as a basis for their quantitative determination. Either the pentose is determined by Fehling's method 7 for reducing 'Based upon six years' experience as chemist to a starch factory. 2 Uber den Rohrzucker des Maiskorns, etc , Inaugural Dissertation zur Erlangung der Doctorwiirde, Gottingen (1889); Journal fiir Landwirtschaft (1889) 37, 503. 3 Landwirtschaftliche Versuchs-Stationen (1887) 34, 403. 4 Le Stazioni Speriment, Agrar. Ital. (1889) 17, 266; Central-Blatt fur Agri- cultur-Chemie (1890) 19, 352. 5 American Chemical Journal (1891) 13, 73. 6 Two pentosans are well known: Xylan, found quite commonly in grains and grasses; and araban, occurring especially in gums such as arabic, tragacanth, cherry, etc. Xylan and araban have the same empirical molecular formula, but they may be distinguished by the difference in the specific rotation and melting points of the respective pentoses, xylose and arabinose, into which they are converted by hydrolysis. For xylose [a]D = i8 to 19 and M. P. = 144 to 145; while for arabinose [a]o=io3 to 105 and M. P. = i54 to 157. Cf. Koch, Pharmaceutische Zeitschrift fiir Russland (1886) 25, 619 and other pages; Berichte der deutschen chemischen Gesellschaft (1887) 20, III, 145; Bauer. Landwirtschaftliche Versuchs- Stationen (1889) 36, 304; Stone and Tollens, Annalen der Chemie (1888) 249, 227; Wheeler and Tollens, ibid. (1889) 254, 304; Schulze, Zeitschrift fur physiologische Chemie (1890) 14, 227; (1892) 16, 387; (1894) 19, 38. 7 Bauer, Landwirtschaftliche Versuchs-Stationen (1889) 36, 304; Stone, Ameri- can Chemical Journal (1891) 13, 78. 1898.] CHEMISTRY OF THE CORN KERNEL. 167 sugars; or the furfurol is determined, preferably by precipitation with phenyl hydrazine as a hydrazone (CsH^ONgHCgHj) 1 . Stone found corn bran to contain 1.25 to 2.67 per cent, of pento- sans. 2 Schulze, 3 after separating considerable other matter from corn bran, obtained a residue which yielded 43.37 per cent, of a pentosan which he showed to be xylan. 4 In 1896 Stone 5 reported a somewhat extended study of the carbo- hydrates of corn, in which sucrose, dextrine, starch, pentosans, and fiber were determined quantitatively. The general method employed may be briefly described as follows: Sucrose. Finely ground corn meal was extracted with 95 per cent, alcohol which was then evaporated nearly to dryness, the residue taken up with water, treated with hydrochloric acid, the inverted sugar estimated by Fehling's solution and calculated to sucrose. Dextrine. The residue of meal was extracted with cold water which was then evaporated to a small volume, the dextrine being precipitated by alcohol, inverted by hydrochloric acid, and estimated by Fehling's solution. Starch. A known proportion of the residue of meal was treated with malt extract, the solution hydrolysed and the sugar obtained estimated by Fehling's solution, and calculated to starch. Pentosans. The residue from the starch determination was boiled with i per cent, hydrochloric acid, the pentose formed estimated by Fehling's solution and calculated to xylan. Fiber. The residue still remaining was boiled with 1.25 per cent, sodium hydroxid, and the insoluble matter (less ash) given as fiber. A sample of corn which contained 80.69 P er cent, of total carbo- hydrates, when estimated "by difference," gave by the above method the following results: Sucrose o . 27 per cent. Dextrine 0.32 Starch 42.50 " Pentosans 5. 14 Fiber 1.99 Total carbohydrates 50.22 " 'Flint and Tollens, Landwirtschaftliche Versuchs-Stationen (1893) 42, 381. Cf. Berichte der deutschen chemischen Gesellschaft (1891) 24, II, 3575; (1892) 25, II, 2912. 2 The results were published (American Chemical Journal (1891) 13, 73) in terms of furfuramid, but are here calculated to pentosan. 3 Zeitschrift fiir physiologische Chemie (1894) 19, 41. 1 The statement by Stone (U. S. Dept. of Agr.. Exp. Station Bui. (1896) 34, 16) that Tollens and Flint (Berichte der deutschen chemischen Gesellschaft (1892) 25, II, 2916) had estimated the amount of pentosans in corn bran to be 38 17 per cent, appears to be erroneous, as the work referred to was with corn cobs (Maiskolben) . r> U. S. Dept. of Agr., Exp. Station Bui. (1896) 34. 1 68 BULLETIN NO. 53. In discussing his results, Dr. Stone says: " This method not only permits the separation of the more delicate and easily decomposed carbohydrates from those which offer greater resistance to -reagents, but from the very beginning of the process any carbohydrate not wholly removed at any particular step would hardly fail of being detected at the next succeeding and more searching reaction. It is considered pertinent to the subject under discussion to call attention to the apparent discrepancy between less than 50 percent, of carbohydrates found in our most prominent cereal grains by direct and fairly accurate methods of determination and the 70 to 80 per cent, commonly ascribed to them by the indirect method of estimating ' by difference.' From 20 to 30 per cent, of the grain or flour is not accounted for. Under the conditions this matter cannot be conceived of as possessing a similar nature to the sugars, starches, or even the more easily soluble forms of gum or celluloses." When we remember that Krocker had shown (see page 165) by a direct and positive method that corn .contains over 65 per cent, of ferment- able 1 carbohydrates (at least almost entirely starch), and that Archbold, from long experience in the manufacture of corn-starch, reports over 60 per cent, of starch present in corn and at least 55 per cent, actually recovered in the commercial process (see page 166), the previously exist- ing evidence of an error in Stone's results is apparent. Dr. Stone has subsequently discovered and reported 8 a large error in the starch de- termination, due to the use of too dilute hydrochloric acid and consequent imperfect hydrolysis. The percentage of starch is now given as 65.45 instead of 42.50 as first reported. The total carbo- hydrates thus found by determination become 73.17 per cent, as compared with 80.69 per cent, estimated by difference. Dr. Stone concludes that: "This discrepancy may arise from one of two sources, tviz. : i. Error in the determination of the carbohydrates. 2. The existence of a substance which is free of nitrogen and is of a character not usually ascribed to carbohydrates and resistant to the ordinary reactions for such. While the first alternative is not excluded, the writer is inclined to the latter conclusion and expects to continue the investigation along this line." In a recent report of extended investigations of methods for the estimation of starch, Wiley and Krug 3 refer to their experiments with the conversion of starch into maltose and dextrine by the use of malt extract, as follows: " The residues from the diastase digestion were all thoroughly washed with hot water and then examined with iodine under the microscope. In every case a large number of cells was found which contained undigested starch, showing that the sample 4 had not been ground to a sufficient degree of fineness. This is, therefore, J The pentosans are classed as strictly non-fermentable carbohydrates. Cf. Koch, Pharmaceutische Zeitschrift fur Russland (1886) 25; Stone and Tollens, Annalen der Chemie (1888) 249, 257; Stone, American Chemical Journal (1891) 13, 82. 2 Journal American Chemical Society (1897) 19, 183, 347. 3 Ibid. (1898) 20, 255 4 A sample of wheat previously analyzed by Stone. 1898.] CHEMISTRY OF THE CORN KERNEL. 169 another source of error in Professor Stone's work. The sample was then reground and the starch determined The residues were again examined and in every case found free from starch, showing that the conversion had been complete. . . The number for starch thus obtained, added to our per cents, of the other con- stituents gives us a total of 99.28." In summarizing their results Wiley and Krug express the following opinion: "The small quantity of matter unaccounted for in the cereal grains is doubtless of a carbohydrate nature, belonging to that complex class, pentosan-ligno-celluloses, whose chemical and physical properties are so nearly alike as to make their exact separation and determination extremely difficult. The quantity of these undeter- mined bodies in cereal grains is very minute." THE OIL OF CORN. The presence of oil in the corn kernel was dis- covered by Bizio 1 in 1823. A partial analysis by Hoppe-Seyler 2 gave the following as the percentage composition 3 of the oil: Cholesterol 2 . 65 Protogon 3-95 Saponifiable fats etc 93-4 The statement is made that the oil contains stearin, palmitin, and much olein, and the melting point of the fatty acids is given as 51 to 54 F. [n] to 12 C.]. Some of the so called physical and chemical " constants," which have been determined by several investigators are given below: Specific gravity Unsaponifiable lodin of oil. substance, absorption, (at i5C.) (percent.) (per cent.) Spuller 4 1.35 "9-7 Smith 5 0.9244 .... 122.9 Hart 6 0.9239 1.55 117.0 Rokitianski 7 ... 0.8360 75.8 The oil used by Spiiller was the ordinary ether extract. Rokitianski used a petroleum ether extract. Hart worked with a "dark brown" sample presumably found on the market. Smith's material was obtained on the market, but was of a " bright golden color" and was probably a fair sample of corn oil. 'Journal fiir Chemie und Physik (1823) 37, 377. 2 Medicinische-Chemische Untersuchungen, 1, 162; Bulletin Society Chimique de Paris (1866) [2] 6, 342; Jahresbericht iiber die Fortschritte der Chemie (1866) 698. 3 I have not been able to see Hoppe-Seyler's original paper. Presumably the protogon is the substance now termed lecithin, and the methods employed in esti- mating it and cholesterol were similar to those which are discussed herein. -Polytechnisches Journal (Dingier) (1887) 264, 626. "'Journal Society Chemical Industry (1892) 11, 504. e lbid. (1894) 13, 257, from Chem. Zeit. 17, 1522. 7 lnaugural Dissertation, St. Petersburg (1894); Pharmaceutische Zeitschrift fiir Russland (1894) 33, 712; Chemisches Central-Blatt (1895) [4] 7, I, 22. 1 70 BULLETIN NO. 53. [faty, Spiiller observed that the oil absorbed no oxygen from the air even after fourteen days' exposure. Smith states that the freezing point of the oil is below 20. Hart gives the melting point of the fatty acids as 25. Rokitianski reports further qualitative chemical work which showed the oil to contain oleic and linolic acids. It is evident from the specific gravity and the iodin absorption that the material with which he worked was not ordinary corn oil. Willey and Bigelow 1 have recently found the heat of combustion of oil of corn to be 9280 calories per gramme. EXPERIMENTAL. In a preliminary study a small amount of oil was obtained by collecting the ether extract from a large number of proximate analyses of corn. In this, advantage was taken of the fact that the oil is moder- ately soluble in alcohol when hot and but slightly so at ordinary temper- atures. 2 The oil was transferred from the small flasks, used in its extraction, by means of hot alcohol to a single vessel. On cooling the oil precipi- tated and settled to the bottom, the alcohol being each time decanted from the collected oil and used in transferring the next lot. Finally the alcohol was evaporated and the oil dried to constant weight in a water oven. When freshly obtained from white dent corn the oil is nearly colorless, but on standing a pale yellow and finally a deep golden color develops, plainly indicating a gradual change in its condition, presumably due to absorption of oxygen. This was confirmed by deter- mining the iodin absorption which was found to be 115.5 percent. A large quantity of corn oil, including samples from four different sources 3 , was then secured in order to make a more thorough investiga- tion. The oil is obtained as a by-product in the manufacture of corn- starch and glucose-sugar, and all of the samples secured were of a pale straw color and evidently fresh and pure. Specific Gravity. Three of these samples of corn oil were sufficient in quantity to enable me to make determinations of their specific gravity by means of a delicate Westphal balance which by trial gave the specific gravity of pure water at 15 as i.oooo. The samples of oil gave the following results: T. 2. 3. Specific gravity .... (15) 0.9245 0.9262 0.9258 1 Journal American Chemical Society (1898) 20, 309 2 Smith has found the solubility of corn oil in alcohol by volume to be 2 per cent, at 16 and 13 per cent, at 63. 3 Samples of corn oil were very kindly furnished me by President Wm. F. Piel, Jr., of The National Starch Manufacturing Company, New York City; by The Chas. Pope Glucose Company, Geneva, 111.; by The Glucose Sugar Refining Company, Chicago; and by Messrs. Elbert and Gardner, New York City. 1898.] CHEMISTRY OF THE CORN KERNEL. 1 71 Melting Point. Preliminary experiments confirmed the observation of Smith that the oil is still fluid at 20, a temperature of 23 (obtained with snow and concentrated sulfuric acid) failing to solidify the oil. It was found, however, that the oil became hard and solid at about 36. The melting point was determined by a modification of the method of the Association of Official Agricultural Chemists 1 . In a tall beaker of about 2.5 liters capacity was placed a small quantity of concentrated sulfuric acid (to absorb water vapor so that the apparatus would remain transparent at low temperatures). A second beaker of about 2 liters capacity was placed in the first, being sup- ported by the rim without touching the bottom. A i -liter beaker taller than the second was placed in the latter and filled with alcohol, the space between the two being filled with solid carbon dioxid. A glass tube 30 mm. in diameter and closed at the bottom was fitted into the inner beaker with a large cork, the tube being about one-third filled with a mixture of x volume of concentrated sulfuric acid and 3 volumes of absolute alcohol, and then nearly completely filled with absolute alcohol. The temperature of the alcohol in the beaker was kept uniform throughout by constant stirring with a wire which passed through the cork and terminated in a ring surrounding the glass tube. A heavy glass spoon and a glass spatula were placed in the alcohol. When the temperature reached 50, the spoon was removed and a drop of the oil at once let fall upon it. A thin, solid, white, opaque disc formed and was quickly made to drop into the inner tube by using the glass spatula. The disc of solidified oil settled through the absolute alcohol to the denser liquid below and th^ere remained in suspension. The beaker which had contained carbon dioxid was replaced by another and the temperature allowed to slowly rise. An alcohol ther- mometer was used for reading the temperatures below the freezing point of mercury. Above 38 a delicate mercury thermometer was employed. As the temperature rose the disc remained unchanged until at 19 it began to lose its opacity. At 14 it had become perfectly trans- parent, but no change in shape could be detected below 7. The disc was much contracted and thickened at 5 and became entirely symmetrical in form at 2.3. A second determination gave practically the same results, the final reading being 2.4. The change in temper- ature (when near the melting point) required 5 to 6 minutes for one degree. To determine the change in the consistency of the oil, a thin-wall tube of 8 mm. diameter, closed at the bottom, and containing i cm. of 'U. S. Dept. of Agr., Div. of Chem. Bui. (1895) 46, 34. 172 BULLETIN NO. 53. \_J l dissolved in boiling 95 per cent, alcohol. On cooling, the sativic acid separated in the crystalline form, melting at 161^-16$ . By distilling the ether from the solution obtained as above described, a brown residue (9.5 gms.) was obtained which melted at 55 to 60 and showed an iodin absorption of only 9.2 per cent. The aqueous acid solution from which the insoluble organic acids had been precipitated by hydrochloric acid was evaporated nearly to dryness, a black tarry mass gradually separating, showing that, although a small amount of unsaturated acids had been unacted upon, the oxida- tion had gone far beyond the simple addition of hydroxyl groups to the unsaturated compounds. To further investigate the fatty acids, a method essentially that of Muter 1 was tried for their separation and determination. It is based upon the fact that the lead salts of the unsaturated acids, oleic, linolic, etc., are soluble in ether; while the lead salts of the saturated acids, stearic, palmitic, etc., are not. About 1.5 gms. of the oil were saponified with alcoholic potash and the soap dissolved in water, the unsaponifiable substance (cholesterol) being separated from the soap solution by shaking with ether. The solution was then neutralized with acetic acid, and the fatty acids pre- cipitated with lead acetate, a slight excess being added. The lead salts were washed with water, and then transferred with 50 cc. of ether to a glass cylinder of about 60 cc. capacity, which was stoppered and then violently shaken for 5 to 10 minutes. The small quantity of matter in- soluble in ether was then allowed to settle. A stopper carrying two glass tubes similar to those used in the ordinary washing bottle was placed in the cylinder, the long tube reaching nearly to the undissolved sediment. By blowing in the short tube the clear solution is transferred almost completely without disturbing the sediment. The undissolved substance was then shaken with more ether, allowed to settle, and the ether transferred as before as completely as possible. This treatment was twice more repeated. The undissolved lead salt was then warmed with about 25 cc. of dilute hydrochloric acid, till the fatty acids sep- arated; and, after cooling sufficiently the whole was transferred to a 250 cc. graduated bulb tube, ether being used to complete the transfer. The portion of the tube below the bulb contained 50 cc. and was graduated to 0.2 cc. A small glass tube carrying a stopcock was sealed in just below the 50 cc. mark. The tube was filled to the 250 cc. mark (above the bulb) with ether, and thoroughly shaken. The aqueous layer, containing the excess of hydrochloric acid and the precipitated lead chlorid was allowed to separate. The volume of ether solution was observed, and 200 cc. of it were Analyst (1877) 2, 73. 1898.] CHEMISTRY OF THE CORN KERNEL. 179 drawn off into a weighed flask, evaporated to dryness, and the weight of the residue determined. Duplicate determinations gave the following : Oil taken 1.600 1.610 gms. Volume of ether solution 222 .4 221 .o cc. Ether solution taken 200.0 200.0 cc. Saturated acids obtained 0.0670 0.0648 gms. Saturated acids in oil 4 . 66 4-44 P er cent. The residue of saturated acids formed a white solid mass. It was dissolved in hot alcohol and allowed to crystallize. The melting point was 57. The quantity of the saturated acids thus obtained was con- sidered too small for further satisfactory examination (see foot note below). Before the lead salts of the saturated acids were completely washed by decantation 1 the clear ether solution of the lead salts of the unsat- urated acids absorbed oxygen, and became cloudy, a white precipitate' forming in considerable amount. Two samples of the atmosphere in the cylinders above the solutions were drawn off in gas burettes; and, after removing the ether vapor, the residual air was found to contain only 15.3 per cent, and 13.9 per cent., respectively, of oxygen instead of 20.8 per cent, as found in the air of the laboratory. By subtracting the percentage (4.55) of saturated acids found in the oil from that of the total fatty acids (93.57) the amount of total unsaturated acids is found to be 89.02 per cent., consisting of oleic and linolic acids. (The melting point of the sativic acid obtained and the composition of its potassium salt prove the absence of linusic acid in the products of oxidation, and, hence, of linolenic acid in the total fatty acids.) From the iodin absorption, the amounts of oleic and linolic acids can be accurately determined. Thus: Oleic acid, C 18 H 34 O 2 -|- I, = C tH H 34 I 2 O2, diiodo stearic acid. Linolic acid, C la H 32 O 2 -j- 2l 2 = C 1B H 3 .jl 4 O 2 , tetraiodo stearic acid. As 89.02 gms. of these unsaturated acids in the ratio in which they exist in corn oil absorb 122.3 gms. of iodin, the following equation can be stated, x being the number of gms. of oleic acid: 254 508 'At least two days' time is required for this process, and even this was found more satisfactory than filtration. I have no doubt that, if centrifugal force were substituted for gravity, the washing by decantation could be done much better and so quickly that the unsaturated acids could also be determined before the absorption of any appreciable amount of oxygen. Quantities of the separated materials sufficient for further examination could doubtless be obtained in a short time. No suitable centrifuge was at hand for this work. l8o BULLETIN NO. 53. LA^'> 1898. The oleic acid is found to be 42.92 gms. and the linolic acid 46.10 gms. By subtracting from the amount of saturated acids the equivalent of the -stearic acid contained in the lecithin, and calculating to the respective glycerol esters the remaining saturated acids (as stearic acid), the oleic acid, and the linolic acid, the following summary is obtained as the composition of the oil of corn: Cholesterol i . 37 per cent. Lecithin 1.49 " " Stearin (?) 3.66 " Olein 44 . 85 " Linolin ; 48.19 " Total 99 . 56 C. G. HOPKINS, PH. D., Chemist. WCA UNIVERSITY OF ILLINOIS-URBANA