A NEW FORM OF CATALYTIC PLATINUM BY VANDERVEER VOORHEES B. S. University of Illinois, 1921 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN CHEMISTRY, IN THE GRADUATE SCHOOL OF THE UNIVERSITY OF ILLINOIS, 1922 URBANA. ILLINOIS Digitized by the Internet Archive in 2015 https://archive.org/details/newformofcatalytOOvoor I 9£/ «_x K; THEORETIC A L The Catalytic Process. The catalytic activity of platinum was first noticed in 1317 by Edmund. Davy when he discovered that a platinum wire in- duced the combustion of inflammable vapors (methyl alcohol, ether, etc.) at tempera tures A below their kindling point. Later experi- ments showed that by carefully reheating the wire in air a number of times, the temperature at which it would glow spontaneously could be lowered to 50°c. A practical use and scientific curiosity resulting from the above discover;; was Davy's glow lamp, a coil of platinum wire suspended above a volatile, inflammable liquid. Shortly after this^Davy prepared platinum in a very fine tate of division by digesting the nitrate (?) with alcohol and ob- tained essentially the product known as "platinum black." This na- erial was a black amorphous powder having the same catalytic pro- perties as the platinum wire but to a much greater extent. It would gnite an inflammable vapor at ordinary temperature and sometimes ex- lode weakly on heating. Since this time numerous modifications have oeen made in the method of preparing platinum black, many uses have peen found for the material because of its remarkable catalytic ac- lvity and many theories have been proposed to account for its pecu- iar properties, but today after more than a hundred years of Pt' H 0 0 H H 0 H 0 v 0 H Tillstatter^ c has assumed the formation of an oxyperoxide of plati- num in oxidation: > 0 0 0 H Pt + °2 p t ’ Pt Oo + HoO ---> Pt «--- x 0 V 0 H and a hydro platinic acid in reduction: 0 H\ / 0 Pt ^ ' + H 2 ---> Pt ' ^ 0 W N o (1) C. C. (1835) 458 Ber. 41, 1984, 1998 (1911) (2) Ber. (1921) 113 ' : - 3 - The adsorption theory has many weaknesses. It does not readily explain the reduction of H N 03 * K Cl 0^ etc. by dextrose in the absence of hydrogen gas . ^ ; It encounters great difficulty in explaining the lack of catalytic activity of platinum in hydrogen when entirely freed from oxygen. ^ Careful experiments by Mond, Ramsay and Shields showed that platinum black contained oxygen, the bulk of which is not liberated until the temperature is raised to 400°. Also, the platinum black would absorb 300 volumes of hydrogen, 200 volumes combined with the oxygen present, and the heat of absorption corresponded with the heat of formation of the water produced, and that the remainder could be removed at 250°. An increase of pressure from 1 to 4 atmospheres has almost no effect on the quantity of either hydrogen or oxygen absorbed. Platinum charged with oxygen absorbs still more on heating to 360° , whereas platinum charged with hydrogen and heated to 360° loses the dissolved gas. From the above data, the postulation of hydrides of platinum as the active catalytist in reduction seems quite unsupported. The oxide theory has been assailed by the adsorpt ionlsts as ansound on the ground that oxides of platinum do not exist. The jreat resistance of platinum to oxidation is attested by its use in analytical crucibles etc. where the slightest oxidation would be fatal -o accuracy. However, that oxides of platinum do exist has been dem- onstrated conclusively by numerous investigators. Following are refer, onces to the results of some of them: (1) Bull. Coll. Agr . Tokyo Imp. Univ. 7, 1-6 (1906) (2) Ber. (1921) 113 (3) Proc. Roy. Soc . 58, 242 (1895) - 4 - “ ' “ — — — ' ‘ Topstte^' ^determined the composition and properties of Pt 0.- prepared in the manner of Doebereiner, Wittstein and Fremy. Na Pt Clg is treated with excess Na 0 H and on acidification with acetic acid a hydrated Pt Og is precipitated. Pt Og’4 HgO loses 2 HgO at 100° Frost ^ ^dissolved the above hydrate in H N 0„ and on dilution obtained Pt Og * 3 PlgO. .Ln 1877 Thomsen^ ^obtained Pt 0 by boiling potassium chloro- platinite (Kg Pt Cl^) with alkali. It is a strong oxidizing agent, converting formic acid to C Og . In the same year, Jorgensen^ 1 2 3 4 5 6 ^ pre- pared what he called "plat inoxydul oxide" by a sodium carbonate fusioi of Nag Pt Clg. It is a bluish black powder, stable to aqua regia and heat, and is reduced by hydrogen and by formic acid in the cold, the latter yielding C 0 . Analysis showed a composition, Pt- 0/. By heating platinum sponge with Nag 0^f } a rapid oxidation of the platinum takes place, Pt g 0, being produced. It is a yellow pow- der when hydrated but on heating to 450° a dark brown powder results 'Thich is only slowly attacked by aqua regia. By electrolysis of fused sodium or potassium nitrates between electrodes of platinum foil, iittorf obtained yellowish brown and green oxides of platinum. Electrolysis of an alkaline solution of Pt Og between plati- ium electrodes produces a reddish brown powder at the anode which has (1) Ber. 3, 462 (1870) (2) Ber. 19 Ref. 666 (1868) (3) J. Prakt. Chem. (2) 15, 284 (1877) (4) J. Prakt. Chem. (2) 16, 344 (1877) (5) Am. Chem. J. 28, 59 (1902) (6) (J. C. (1848) 23 ^5 = the formula, Pt 0. t . ^ 1 ^ It is not reduced by H g Og but dissolves in dilute H Cl with evolution of chlorine. It loses oxygen readily, forming Pt 0 2 on heating. In his classic paper on platinum' '7 T 6hler has shown that pla- tinum black has the property of oxidizing K I to iodine as indicated by the starch test. From its partial solulility in H Cl, he has cal- culated it to contain 10-18% Pt 0. By an oxidation in oxygen gas at 450° Wtthler obtained 44% of platinum sponge converted to platinum ox- ide. Since platinum black behaves very similarly to Pt 0, Wfthler as- |! signs its catalytic properties to this substance. Wi 11s tatter <3>has now shown that platinum black used in cata-l lytic reductions is ineffective when deprived of its oxygen, and that catalysis is resumed after the catalyst is exposed to air or oxygen gas. Much work has been done on the poisoning of platinum catalyst' and it is seen that most "poisons" are reducing agents. Platinum ( 5 poisoned with H C N may be revivified by a current of air or oxygen. The necessity for oxygen is hard to explain on any other assumption than that an oxide of platinum is the active catalyst. The stability of some of the platinum oxides is quite re- markable. Pt 0 does not decompose appreciably below 400°. Pto 0 S and Pt^ 0 4 are stable at higher temperatures than this altho Pt 0g loses half its oxygen at 280°. Pt Cf reverts to Pt Og on gentle warm- o ( 1 ) Ber. 42, 3326 (1909) (2) Ber . 36 , 3475 (1903) (3) Ber. (1921) 113 (4) Zeit . Physikal. Chern. 37, 1-68 (1901) (5) Zei t . Physikal. Chem. 37, 551 (1901) , “ ■ - 6 - ing altho my experiments show that an oxide higher than Pt Og is quite stable at somewhat elevated temperatures. Pt 3 0 4 retains half its oxygen until a temperature approaching 1000° is reached. The volatilization of platinum in electric furnaces at com- paratively low temperatures followed by crystallization on the cooler portions of the furnace, has been explained by Roberts ^ 1 2 3 ^by the form- •2V ation of Volatile oxide at the higher temperature which is unstable at the lower one. This theory is supported by the fact that volatil- ization does not take place in an atmosphere of hydrogen, nitrogen 02 in a vacuum. Furthermore a similar phenomenon occurs with the chlor- (o) (3) ides' ' and with the fluorides. (1) Phil. Mag. 25, 270 (1913) (2) Compt. Rend. 947 (1877) (3) Compt. Rend. 807 (1889) = 3 = Preparation and Uses of Platinum Black. *- Many methods have been given for the preparation of platinum black, each claiming an advantage over those previously employed. However, almost all of them have this in common, the precipitation of the platinum from a solution of Pt CI 4 by a reducing agent in the presence of an alkali. The first laboratory method for making platinum black was originated by Liebig^'^in 1829. He boiled Pt Cl g with Kg 0 0^ and alcohol, which is essentially the same as the preparation of Pt 0 as given by Thomsen.^" ^ In 1854 Doebereiner ' ' '^reduced Pt Cl^ with ( 4 ) sugar or alcohol in a sodium carbonate solution. Later, Hempel ' ( 5 ) and also Brunner reduced Pt Cl in alkali by means of ferrous salts ( 5 ) Fond, Ramsay and Shields v 'precipitated platinum black from Pt Cl^ by sodium formate in sodium carbonate. Very active platinum black (7) can be produced by boiling Pt Cl^ with Rochelle salt and with gly- ( 8 ) cerol and K 0 H. It has also been made by passing hydrogen over *2 Pt Cl^ at 250°^“^ and by reduction of Pt Cl, with aluminum foil .^ 0 •?:- Footnote--In German literature platinum black is termed " Platin- mohr" from the word Mohr meaning Moor or black. (1) Pogc. Ann. 17, 102 (1829) (2) J. Prakt. Cbem. (2) 15, 294 (1877) (3) Ann. 2, 1 (1834) (4) Ann. 107, 97 (1857) (5) Ann. 109, 253 (G) Trans. Roy. Soc. 660 (1895) (7) C. C. (1877) 576 ( 8 ) Bull. Soc. Chim. 25, 198 (1876) - 8 - The most widely used method at present is that of Loew^in which he reduced Pt Cl with formaldehyde in the presence of sodium hydroxide. The reduction is incomplete and the platinum black is semicolloidal until it is exposed to air on the filter. Air is ab- sorbed accompanied by a rise of temperature and loss of colloidal na ture . Two recent methods are modifications of this last, the object being to facilitate the preparation by avoiding the colloidal form ( 2 ) which makes washing and filtering difficult. Feulgen 'shakes the precipitate with acetic acid when it tends to become colloidal. Aftejb thoro washing by decantation the black is dried in a vacuum and on exposure to air it absorbs oxygen so rapidly that it glows with the heat of reaction, Willst&tter ^ ^conducts the reduction at low tem- perature and employs K 0 H vhLch gives the crystalline and relatively coarse Pt Clg, thus bringing down the platinum black in particles which permit ready decantation. Platinum black is finding considerable use in the catalytic reduction of organic compounds and has been used in inorganic reduc- tions and oxidations for some time; N has been oxidized by air to (4) N H 4 N Og and S Og to S 0^ in the "contact process." Nitrogen has „ (5)_ _ „ _ „ TT (S') , „ - 9 - Vavon^ 1 2 Ogives a good review of the organic reductions hy platinum black. Acetaldehyde, isoamylaldehyde and heptaldehyde yield the cor- responding alcohols while acetone, ethyl methyl ketone and diphenyl ketone were reduced to the secondary alcohols . Palladium black is generally conceded to be a more active cata lyst than platinum black and my own experiments have borne this out. However, its action is peculiarly different from that of platinum. While platinum reduces benzene to the hexahydro benzene, palladium ( 2 ) reduces it only to the tetrahydro derivative. In my experiments I reduced salicylaldehyde rapidly with palladium black to ortho cre- sol, a product which was never obtained in the use of platinum black under widely varying conditions. (1) Ann. Chim. Ser. 9, 1, 144 (2) Zeit. Anorg. Chem. 191 (1900) , ■ , . - 10 - Exper imental Assuming that the catalytic property of platinum black is due to an oxide, of which it contains only 18-20^, it would appear that the pure oxides of platinum themselves, particularly the higher ox- ides, would be far more active catalysts than platinum black as usu- ally prepared. Accordingly an oxide of platinum was prepared in the following manner: 1 gm. of platinum was dissolved in aqua regia and the result- ing solution was mixed with 10 gm. Na N O 3 . The mixture was rapidly evaporated to dryness and fused over a Bunsen flame in a small porce lain casserole or Pyrex beaker. Between 300° and 400°, red oxides of nitrogen are given off and the platinum is precipitated as a f^ne powder ranging in color from a light yellowish brown to a dark red- brown. When the evolution of oxides of nitrogen has ceased, the fu- sion is poured into a cool casserole and allowed to solidify. When cold, it is dissolved in water and decanted twice from the oxide thru a filter. The oxide is then transferred to the filter and washed several times until free from nitrates. The powder may be used dir- ectly or dried and used at intervals . All filtrates should be tested for platinum by the method of Wtthler^^. To an acidified portion is added a few drops Sn Cl,-, sol. A yellow or brown color indicates platinum, the intensity varying witfli the quantity. The color may be shaken out with ether or ethyl acetat thus giving a very sensitive test. The filtrates containing platinum (1) Chem. Zeit. 31, 938 (1907^ • ■ . ' . , . . - 11 - should be evaporated and re-fused with a little sodium carbonate which will throw cut the platinum quantitatively as a black powder. Altho this method has not been found in the literature, Jor- gensen and Dudley ( ^both obtained platinum oxides by fusion methods , and it was thought that fusion with a strong oxidizing agent like Na N Og would produce a higher oxide . If a mixture of h N 0 5 and Na N O 3 is used in place of Na N 03 , the fusion point is much lower, but the oxide seems to be in a less finely divided form, since the crystalline, insoluble potassium chloroplat inate is first formed. Consequently the resulting catalyst is less active. Preparation of the catalyst at different temperatures . 2-g gram samples of platinum were dissolved In aq . reg . and placed in 50 CC porcelain crucibles with 10 grams of Fa N each. These were heated carefully in an electric resistance furnace, the temperature being controlled by an outside resistance and the fusion being constantly stirred by a thermocouple encased in a Pyrex tube Sample I Time Temperature Remarks 0 min . — Placed in furnace 4 " 295° Pus ion 5 " 305° Evolution of N O 2 begun 25 " 385° Decomposition almost Complete 35 " 415° Evolution of N 0 q ceased 40 " 382° Removed from furnace ( 1 ) loc . cit. (*-) Temperature readings were made by Mr. T. 0. Yntema. . - 12 - Sample II Time Temperature Remarks 0 min . — Placed in furnace 9 it 280° Fusion 13 tt 320° Evolution of N o^ begun 20 tt 415° Rapid evolution of N Og . Exotherm! 26 11 465° Decomposition almost complete 32 tt 555° Odor of N Og still noticeable 48 tt 504° Removed from furnace Sample III Time Temperature Remarks 0 min . — Placed in furnace 5 it 290° Fusion 10 rt 425° Rapid decomposition 23 rt 580° Evolution of N Og praotically osase 29 ii 655° 41 it 680° Still faint odor of N 0^ 48 tt — Removed from furnace After cooling the melts were extracted with water, filtered and washed free from nitrates . The filtrate from No. I showed a con- s iderable quantity of platinum in solution, but No. II and No. Ill filtrates contained only a trace. After drying in a dessicator over H 2 S 0 4 the three samples were tested for catalytic activity by the reduction of salicyl alde- hyde under similar conditions as follows: .5 gram of the catalyst was placed in a 400 C.C. bottle with 30 gm. salicyl aldehyde and 100 C.C. alcohol. The air was exhausted from the bottle and hydrogen was admitted from an 8 liter tank equippe i - 13 - with a pressure gauge. The amount of hydrogen absorbed can be close- ly calculated from the fall in pressure. A drop of 21.3 pounds is equivalent to 1 gm. Hydrogen, and variation of pressure with room tern perature was corrected for. The bottle was suspended in a stirrup and oscillated by a motor-driven crank which produced a constant and violent agitation of the contents. After reduction, the alcoholic solution of saligenin was separated from the catalyst, the alcohol distilled off under diminished pressure and. the saligenin crystallize from benzene in shining white plates. No attempt was made to obtain the exact yield, the approximate yield being merely a rough check on the experiment. Sample I Olive drab amorphous powder. Pressure Time 30.0 lbs . 0 : 00 hr 24.9 0:11 22.0 0:22 20.7 0:58 20.6 1:30 20.6 2:20 9.4 - Total abs orpti Remarks Catalyst black and bottle quite warm (Theory - 10.2) Catalyst could not be separated by decantation but filtered readily. Yield - 22 gm!. saligenin. . - - 14 - 3 ample II Slightly lighter in color than I Pressure Time Remarks 29.9 lbs. 0:00 28.1 0:50 Catalyst in s emi colloidal state. Olive screen color. 25.2 0:40 25.0 0:50 Bottle warm from heat of reaction 21.5 1:00 19.8 2:17 Catalyst a jet black 10.12 - total absorption Catalyst was difficult to separate and had a tendency to pass through the filter. Yield - 20 gm. saligenin. Sample III Slightly lighter color than II Pressure Time Remarks 29.7 lbs . 0:00 29.3 0:26 ro ~o CD 0:41 26.2 0:53 Catalyst an olive green color 21.8 1:53 20.5 2:33 19 .5 3:43 Catalyst a greenish black i CVJ • o 1 — 1 total absorption Catalyst did not settle on standing over night. On shaking with a few drops of acetic acid it settled completely in two hours. Yield of saligenin - 18 gm. (some loss due to oxidation in handling ) . ■ . . , Ahsorpffn Hy*(rofc~n /n A +*mf - 15 - 30 grams more salicylaldehyde was added to the above catalyst and a second reduction made to show whether or not its slow action was due to lag at start. Pressure Time 30.1 0:00 29.2 0:18 28.9 0:30 27 .5 0:51 27 .2 1:56 23.3 7:11 20.1 12:26 10.0 Yield - 16 gm. sa'ligenin. Analyses of foregoing oxides . After standing in a dedicator over sulfuric acid for 2-gj months, the oxides were analysed by heating in porcelain crucibles at varying temperatures in an electric furnace and finally over a Meeker burner in an atmosphere of hydrogen (Rose crucible) to obtain complete reduction to platinum. Each weighing was made after cooling the crucible in a dessicator in which a vacuum of 1 m.m. was obtainec \ minute after the crucible was removed from the heat. Sample 12 hrs . at 120° Loss of wt . on heating: 2 hrs . at 120° 2 hrs . at 240° 2 hrs . at 360° (No change in color) I II III 1.9528 2.5708 2.3883 .0104 .0220 .0323 .0854 .0073 .0164 -Ie>- ““ 2 hrs. at 700° ----- .2410 (dark gray) 20. min. with Hydrogen .2525 .4312 II III Percentage loss after heating at 120 u 18.9 18.5 Sample II was heated in oxygen over a Meeker burner to con- stant weight and found to absorb 5.21% of its weight of oxygen and become dark in color. Since Pt 0 contains 8.16$ of the wt . of pla- tinum as oxygen, the above absorption corresponds to a conversion of 40$ of the platinum sponge to Pt 0, a value very near that obtained bj WBhler from solubility in H Cl.' 1 1/1 Platinum oxides prepared from various fusion mixtures and their catalytic activity. Various mixtures were prepared and fused rapidly in porcelair over a Bunsen burner, the temperature being gradually raised to 450° within 5 minutes. The melt was stirred constantly with a pyrometer couple enclosed in a pyrex tube.* * Compositions of mixtures: I 1 gm. Pt (as Pt Cl 4 ) t 10 gm. Ha N 0 kJ II 1 gm. 20 gm. It III 1 gm . it + 10 gm. IT f 2 gm. Nag C 0^ IV 1 gm. u 10 gm. " ♦ .2 gm . Carbon (1) Loc . cit. * Temperatures read by Mr. T. 0. Yntema - 17 - The object of the carbon was to reduce some Na N 0^ to Na 9 C O 3 after fusion which would cause complete precipitation of the platinum. Samples I and II were incompletely precipitated. Samples III and IV were almost entirely precipitated. Samples I and II were a medium brown in color. Samples III and IV were a light brown and yellow. The catalysts were tested as follows: 30 gm. salieylaldehyd f 60 C.C. alcohol were shaken with .25 gm. of each catalyst. Result 1 as follows: Pressure Time Remarks Sample I 30.8 lbs . 0:00 28.8 0:11 23.8 0:33 Bottle warm and catalyst black 21.9 1:03 21.1 1:48 Sample 20.8 10.0 II 2:02 29 .6 lbs . 0:00 26 .2 0:15 Bottle warm 23 .2 0:30 21.0 0:55 Sample 20.1 9 .5 IV 2:40 30.2 lbs . 0:00 28.1 0:21 Bottle warm 26.4 0:31 22.8 1:31 . ■ /7 * I±t TF rF t± T+ 5 rq~ i 'i i"j , 1~~T~ hR-'-r ±14- n '■ +-p r- - s - 9 Cf ^ £> S Cf \/ U ^ £ O -/ )* /• +-/ J.O f |l> \t 7~ ? rri e / r\ W / ft h T e ? - 18 - Pressure Time Remarks Sample IV (cont.) 20.9 2:47 20.9 5:17 Qualitative Tests on Brown Oxide of Pl at inum prepared by Na N 0? Fusion . 1. The oxide is only partially soluble in boiling dilute H Cl. In- soluble portion dissolves easily in H Br with evolution of Br^ . 2. It is incompletely soluble in boiling cone. H Cl or aqua regia. 3. It dissolves easily in dilute H Cl on warming with SOg to give the yellow chlorplat inic acid. 4. It is only very slightly soluble in 10$ Na 0 H. 5. It is quite insoluble in boiling concentrated h w Cb . 6. It dissolves easily in constant boiling H Br with liberation of bromine (detected by odor and by shaking out with chloroform) . Bromine vapor may be distilled into K I sol. liberating free I 0 . The platinum goes into solution as Hg Pt Brg and can be precipi- tated as the red, slightly soluble potassium salt. 7. The oxide does not change color on treatment with EgOg (3$) either by long standing in the cold or on boiling. It catalyses the liberation of oxygen, however, both cold and hot. 8. On boiling with alcohol In an atmosphere of C Og it is reduced to a black powder in 3 minutes . The odor of acetaldehyde is detected . 9. When damp with alcohol and exposed to air the oxide will ignite the alcohol. It will also ignite a mixture of hydrogen and air. * , . * , * - 19 - A Comparison of the Catalytic Activity of Platinum Oxide Prepared by Sodium Nitrate Fusion and Platinum Black Prepared by Formaldehyde Re- duction . .5 gm. of platinum was converted to the oxide by a Na 11 0^ fusion and shaken with 20 gm. vanillin + 100 C. C. alcohol. Using the same catalyst, the reduction was repeated four times to test the wear- ing quality of the catalyst. Each time the product (Vanillyl alcohol] was decanted from the platinum, the alcohol evaporated under dim in. press, and the vanillyl alcohol crystallized from hot 'water. Pressure Time First run: 23.1 lbs . 9:00 IS. 6 0:20 18.3 0:35 Yield - 16.5 gm. 17 .6 0:50 It . P . 116° (uncorrected) 17 .0 1:55 (Lit. - 115°) 17.0 2:55 16.8 18 : 00 Total absorpt ion -6 . 3 lbs . ( Theory 5 . Second run: 25.2 lbs . 0:00 23.9 0:20 Yield - IB. 5 gm. 22.0 1:00 11. P. 116° (uncorrected) 21.2 1:20 19.4 3:25 Total absorption-5 .8 lbs . I ft N* 'V to =^55= Pressure Time Third run : 25.9 lbs. 0:00 Yield - 18.5 gm. 22.0 0 : 45 M.P. - 116. 5 C (uncorrected) 20.7 1 : 50 20.5 4:10 5.4 Fourth run: 25.4 lbs. 0:00 Yield - 15.5 gm. 23.3 0:20 M.P. - 116° (uncorrected) 18.7 1:40 (Probably some leakage) 18.0 3 : 30 7.4 Platinum black was prepared according to the directions of Willstatter ^ 1 ' as follows : .5 gm. Platinum as Pt CI 4 was dissolved in 2 C .0 . water to which a few drops of H Cl was added. 3.8 C ,C . formaldehyde (33;1) was added and the solution cooled in ice and salt. 10.5 gm. 50p K 0 H was stirred in drop by drop and a yellow paste formed which gradually darkened to a black mush. The mixture was warmed to GO 0 for -|- hr. and the platinum settled out as a flocculent precipitate. Ibis vas washed by decantation four times with 100 C .C . distilled water and the platinum black washed free from water by alcohol. Still wet with alcohol it vas placed in the reduction bottle with 20 gm. Vanillin t 100 CC alcohol. (1) Ber. 113 (1921) l- Pr e s s ur e T irne . 8 lbs . 0:00 hr . 25 .2 24.8 24.4 24.1 1:45 3:00 6:15 18:45 .4 gm. platinum oxide prepared by Na N 0- fusion now added 23.1 lbs. 0:00 21.5 20.8 20.0 17 .6 0:45 1:55 3:40 20:10 ^ gm. platinum black ^as prepared by the method of Feulgenl^ In this method the platinum is precipitated by formaldehyde anr 1 Na 0 ft and the colloidal black caused to settle by shaking with dil. acetic acid. After drying in a dessicator over Eq 30 4 it was shaken with 20 gm. vanillin in 100 C .0 . alcohol. Pressure Time 23.6 lbs. 0:00 hrs . 25.8 25.4 25.4 24.8 2:00 20:00 25:00 42 : 00 .2 gm. platinum prepared by Na N 0^ fusion now added Bottle warm from heat of reaction 22 .7 18.0 17 .9 0:00 0 : 30 1:05 ( 1) Ps&'o .wan f iQ9i | ! 2 - atalysis by Pt 0 Pt 0 was prepared by the directions of f'&hler ( - )by boiling potassium. chloroplatmite w ith a slight excess of sodium c ’ hone* . ■ . .06 gnu K Pt Cl 4 was dissolved and boiled with Nag C 0,^. Pt 0 was precipitated as a fine black powder, washed thoroughly with hot water and dried over H 2 S 0 4 . On shaking in hydrogen with 20 gm. vanillin n 100 C.C. alcohol, the following results were obtained: Pressure Time 25.7 lbs . 0:00 hrs . 23.6 8:25 22.7 23.45 5 .0 .4 gnu platinum prepared by Na N O 3 fusion now added Pressure drop required by theory - 5.5 lbs. 20.5 lbs. 0:00 hrs. 17 .8 17 .8 2 .7 0 : : ob 6:35 ( 2 ) Pt 0 was prepared after the manner of Thomsen v ; as follows: 1.06 gm. Ko Pt CI 4 containing .5 gm. platinum was dissolved and to it was added the calculated quantity of .1 N. Na 0 H to precipitate Pt 0 on boiling, the Pt 0 was precipitated and washed by decantation until free from the neutral Na Cl solution. It was shaken in hydrogen with 30 gm. salicylaldehyde in 100 C.C. alcohol with the following results ( 1 ) loc . cit. ( 2 ) loc. cit. Pressure 29.5 lbs. 28.0 25.7 .2 gm. platinum prepared by Na N O 3 fusion now added 3 . 8 22.7 lbs. Required absorption (Theoretical) 10.2 lbs. 14.8 14.8 7.9 Time 0:00 hrs. 2:15 17 : 35 0 : 00 hrs . 1 : 50 8:05 Reduction o 1 s thyl methyl ketone. 80 gm. redistilled ethyl methyl ketone were shaken with .525 gm. of red-brovm platinum oxide from Na N O 3 fusion which had been washed with alcohol and ether previous to use. Pressure Time Remarks 45.5 lbs. 0:00 37.0 0 : 15 Bottle quite warm 32.0 0:20 Pressure increased 13 . 5 49.0 0:20 15.5 1:45 Pressure increased. 33.5 40.0' 1:45 33.0 16:45 7.0 • 53.0 lbs. - total absorpt ion (45 lbs. - theory) Yield - 74 gm. sec. butyl alcohol - 98° - 101° - 24 - Reduction of Phenol. 62 gin. redistilled phenol was dissolved in 50 C .C . alcohol and shaken with .65 gin. ftp 1 at inum oxide with the following result Pressure Time Remarks 31 l"bs. 0:00 hrs . 15 0:40 Pressure increased 16 47 0:40 Bottle very warm 10 1:50 Pressure increased 37 50 1 : 50 22 6:30 Pressure increased 28 40 6:30 28.9 21:10 11.1 92.1 - total absorption (Theory - 85) Small amount of unreduced phenol shaken out with Na 0 H. Yield - 54 gm. - 156° - 7 0 Gyc lohexa.no 1 . Reduction of Benzamid. 30 gm. benzamid were dissolved in 100 c.c. glacial acetic acid and shaken in hydrogen with . 5 gm. brown platinum oxide. Pressure Time Remarks 39.3 lbs . 0:00 hrs. 38.6 0:25 Catalyst turned black. 35.3 5:15 33.8 18:30 5.5 No product isolated. . . « ‘ . * . ■ . - 25 - 20 gm. benzamid dissolved in 100 c.c. warm alcohol and shaken with catalyst from above. Pressure Time 30.4 lbs. 0:00 hrs. 23.4 3:30 20.7 7:30 18.5 22 : 30 18.5 28 : 00 Yield - 9 gm. hexahydro benzamid crystallized from alcohol. Shining white plates M.P. 185°. (Lit. 185 - 6°) Reduction of Kept aldehyde . 25 gm. heptaldehyde dissolved in 50 c.c. alcohol was shaken with .5 gm. brown platinum catalyst in hydrogen. Pressure 30.0 lbs, 29.0 Time 0:00 1:25 Remarks Catalyst became black instantly 1.0 22.4 0:00 .5 gm. more catalyst added. 17.3 1:30 16.2 7 :0G 16.2 17:00 6.2 1.0 7.2 total aosorpt ion (theory 9.3) Yield 22 gm. heptyl alcohol 173°' - 175° -26- Palladium 15 gm. palladium was dissolved in aqua regia and fused with 10 gm. Na N O 3 at about 550°. The precipitated palladium was filterei off and washed free from nitrates, the filtrate showing a consider- able quantity of unprecipitated palladium. The catalyst, which was a dark reddish brown and showed a metallic glint in suspension, was placed in the shaking bottle with 30 gms. salicyl aldehyde and 100. cc alcohol . Pressure Time Remarks 32.0 lbs. 0 :CC 2 S .0 0:06 Catalyst blackened in a few 25.5 0:16 seconds. Gathered into flocks 16.9 1:10 which settle at once on stopping 14.6 1:53 17.4 total absorption. shaker , (Theory for saligenin - 10.2) No saligenin could be isclat ed from the reduction product, but 14 gm. ortho cresol was obtained, 185° - 187° which could be easily crystal- lized. A high boiling, syrupy residue remained, probably a con- densation product. A second run was made using the same catalyst. Pressure Time ' Remarks 29.0 0:00 27.8 0:18 Shaken with air 18 min. 1.3 26.0 0:00 21.1 1:22 18.4 2:39 13.3 17:17 ■ - 37 - 13. 7 14.0 - total absorption. Yield - S gm. pure o cresol. In these experiments .2115 gm. palladium was used. The brown palladium oxide showed the same chemical properties as that of platinum, partial solubility in aqua, regia but soluble in H Br only on warming. Iridi um J gm. of insoluble material obtained from platinum scrap assumed to be iridium was shaken with 25 gm. cinnamic acid dissolved in 100 c.c. alcohol. 10 lbs. of hydrogen was absorbed in 2 hrs. and 20 min, A mixture of liquids was obtained and a small amount of aihydro cinna- mic acid was isolated M.P. 48.5 (Lit. - 48.7) * CONCLUSION - 28 - The results of the experiments tabulated fcsre seem to indicate that the brown amorphous powder obtained when Ft CI 4 is fused with Na N 0^, is an oxide of platinum having a higher oxygen content than Pt o a . Its catalytic activity is apparently due to a lower oxide which is formed in the reduction bottle, (probably Pt 0 ) . Its superior activity to Pt 0 is likely due to physical form (state of division), and its superiority over platinum black is probably due to a larger oxide content and to a gradual reduction of the higher oxide to the active form which sustains the catalysis. Its ease of preparation and convenient application should commend its use in place of platinum black, the preparation of which is quite difficult if an active form is to be obtained.