Pi I PRESERVATIVES, PRIORITIES, AND PROCESSES January 1942 • ■ J - J~T U±Sl UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY Madison, Wisconsin In Cooperation with the University of Wisconsin Digitized by the Internet Archive in 2013 http://archive.org/details/presOOfore preservatives, priorities, and processes^ By GEORGE M. HUNT, Chief, Division of Wood Preservation R. H. RAECHLER, Chenist and J. OSCAR BLEW, JR., Associate Technologist Like most other industries at this tine, the wood-preserving industry finds itself facing a serious emergency. Daring the year 1941 wood proservcrs treated a considerably larger quantity of lumber and timber than in 194-0. No actual statistics are available on the amount of material treated in 1941 and it will be some months before such data can be published. The statements made by various individual plant operators, however, indicate strongly that 1941 will show a larger amount of timber treated than any other year since 1930. Whether this rate will be maintained in 1942 depends chiefly upon the demands for new construction for military purposes or munitions production. Creosote Supplies In the face of a great increase in demand for creosoted wood, there has been a substantial decrease in the amount of creosote available owing to a great decrease in the amount of creosote imported. This shortage is felt most keenly by plants on or near the Atlantic, Gulf, and Pacific Coasts, which have depended largely upon imported creosote but it is being felt to some' extent throughout the country. The import statistics for the last quarter of 1941 are not available for publication but for the 9 months ending September 30, 1941, they are reported by the Department of Commerce to have amounted to 12,971,656 gallons, which is probably very close to the total for the year. This is about l/3 of the amount imported in 1940 and about 35 million gallons less than the average importation for the years 1936 to 1940 inclusive, as is indicated by the data in table 1. What the creosote imports in 1942 will amount to, no one can safely predict. There appears to be plenty of creosote in the United Kingdom for export despite its use there for fuel and, presumably, we could look forward to an ample supply if the oil could be transported more freely. Since all 1 — ______ "Presented at the 38th annual meeting of the American Wood-Preservers' Association, Minneapolis, Minnesota, on January 27-29, 1942, R1284 imports and exports are under strict control, however, and are governed prima- rily from the standpoint of military strategy and war-time economy, other factors than the needs of the American wood-preserving industry must determine the creosote import policy in 1942. Those in control realize that creosoted wood is being used very largely on national defense construction, that it is a necessity in the maintenance of our transportation, communications, and power distribution systems, and that it is increasing in importance as a substitute for steel in many types of construction. It seems probable that enough foreign creosote could be allowed to enter the United States in 1942 to avoid plant shutdowns but it is certain that unlimited imports will not be permitted and that surplus stocks of imported creosote will not be accumu- lated. There apparently was a large amount of creosote in storage in the United States at the beginning of 1941. Treating plant operators could see the prospective shortage coming and some of them, at least, kept their stor- age tanks well filled. There was also a large quantity of creosote in the tanks of the creosote producers and importers at the beginning of the year. There is no way to obtain an accurate estimate of the amount of creosote carried over from 1940 but it may have been 30 to 40 million gallons. This was about enough to make up for the shortage in imports and was a very i impor- tant factor in enabling plant operators to increase the volume of timber treated in 1941 despite the shortage of imports. This condition does not ex- ist at the beginning of 1942, however, since the stored creosote has been used up, and both the treating plants and the creosote suppliers have entered the new year with very low stocks. One important supplier reports that, although he will produce considerably more creosote in 1942 than in 1941, he will have less oil to sell in 1942 because he enters the new year with storage tanks practically dry, A factor that has favored creosote plant operators in 1941 is the increase in the amount of domestic creosote produced. This increase is diffi- cult to estimate with any degree of accuracy, but it seems certain to fall considerably short of compensating for the decrease in importations. The increase in creosote production has been brought about by an increase in the amount of tar available for distillation, an increase in the average yield of creosote per gallon of tar distilled and, to a lesser extent, an increase in tar distilling capacity. The increase in the amount of tar produced in the country during 1941 has been a reflection of near-capacity operations of steel mills and coke ovens. However, tar production has by no means run parallel with coke production. The average yield of tar per ton of coal carbonized has fallen aff as a result of the short coking periods which prevailed throughout the year in response to a heavy demand for coke; accordingly, tar production 'v/ill show a much smaller increase during 1941 thaT> will coke production. The increase in tar production has been offset to some extent by the large founts of tar that were burned in open-hearth furnaces, especially during the first half of 1941. Local shortages of fuel oil or of tank cars, in- creased cost of fuel oil, and difficulties of obtaining fuel oil of suitable quality, have all encouraged the use of tar as fuel in open hearths. Thus E1234 -2- Table 1. — Imports of coal-tar creosote from various sources for the years 1936 to 1940 inclus i vei Country Amount of creo 1936 : 1937 sote importec 1938 1939 1940 Gallon. - 16,452 449,794 5,065,074 367,500 Belgium Canada Germany Japan. Kwantung. . . . Netherlands. Russia United Kingdom All others Gallons 7,506,934 1,026,429 4,644,584 4,141,753 24,063,995 Gallon s 9,136,788 2,569,751 2,849,347 5,614,314 859,213 12,329,470 24,815,077 15,567 Gallons 5,891,147 868,177 7,159,220 4,869,725 1,216,250 6,261,601 1,089,340 28,017,758 18,372 Gallons 9,588,787 532,018 4,568,565 5,672,901 2,811,449 6,139,892 22,554,836 8,154 33,110,968 Total 41,383,695 58,189,527 55,391,590 51,876,602 39,009,788 Average annual importation during the five years, 49,170,240 gal, "Data from published reports of U. S. Department of Commerce (Industrial Reference Service, Part 1, Chemicals and Allied Products). R128^ Statistics for 1941, as compared with 1940, are expected to show a large in- crease in coke production, a smaller increase in tar production, and a still smaller increase in the amount of tar avail at) lc for distillation. Other conditions "being the same, the yield of creosote per gallon of tar decreases with the coking period during which the tar is formed. However, a compensating factor has been an over-all increase in the distil- lation residue of the creosote which has been brought about to some extent by a refusal of some distillers to make a low-residue oil out, to a larger extent, by cooperation between producers and consumers. A considerable amount of low-residue oil has resulted from the production of roofing pitch and so- called electrode pitch which is a soft pitch that has been needed in relative- ly large amounts by the aluminum industry. One large steel company has con- tinued to distill to a soft pitch to blend with fuel oil for open-hearth fuel and, in so doing, has produced a low-residue creosote. However, the general trend has been in the direction of higher residues. The outlook for 1942, of course, is uncertain, but indications point to a further increase in domestic production of creosote over that of 1941. The supply of tar available for distillation seems to be the limiting factor; tar distilling capacity has not yet been fully utilized. The active demand by defense industries for coal-tar products other than creosote, es- pecially naphthalene and the tar acids required for the manufacture of plastics, should influence the official policy in a manner favorable to the wood-preserving industry. The O.P.M. apparently has already been responsible for an increase in the amount of tar available for distillation by inducing certain steel mills to substitute fuel oil for tar. It does not seem likely, however, that domestic production alone, even when accelerated to the extent he that may reasonably be expected, can supply all the creosote needed at 1941 rate of consumption. On the other hand, a decrease in demand for ere: soted timber would ease the situation appreciably. Supply of Salt Preservatives The supply of salt preservatives in 1941 apparently was sufficient for we have received no reports that the operation of any treating plant has been hindered by a shortage of salt preservatives, although the amount of timber treated with preservative salts in 1941 was probably somewhat greater than in 1940. This favorable situation will not necessarily continue in 1942, however, for it can very easily be changed by military requirements and the decisions of the controlling agencies. At the time this is written, there seems no ii ediatc danger of a serious shortage of zinc chloride. The supplies of zinc ore and hydro- chloric acid appear to be adequate and there is no immediate prospect th this situation will change but we have ample evidence that changes can take place very suddenly. The amount of zinc chloride used for wood preserving in 1940, including that used straight as well as that in chrouated zinc R1284 -3- chloride, totalled about 4-1/2 million pounds (14) . The 1941 total is, course, not yet available, but it was undoubtedly higher. of Zinc is also a necessary ingredient in zinc-meta-arsenite, of which some 200,000 lbs. were used for wood preservation in 1940, In pre- paring this preservative, the zinc is used in the form of zinc oxide and the aresenic in the form of arsenious oxide (ASpO^) . The supply of either one is not unlimited but has apparently been equal to the need thus far. Chromium salts are, of course, important ingredients in several of the salt preservatives in extensive use. Sodium dichromate makes up about 18 percent of the weight of chromated zinc chloride and about 50 percent of Celcure, while Tanalith (Wolman salt) averages about 37-1/2 percent sodium chromate. The amounts of these preservatives reported used in 1940 (14) and the calculated amounts of chromium salts they contained are as follows: •Preservative : Amount used in : 1940 : Chromium salts included Pounds : 242,739 3,960,896 1,062,048 : : Pounds • 121,370 (sodium di- Wolman salts (Tanalith) ! chromate) 712,961 (sodium di- chromate) 398,268 (Sodium chromate) Total chromium salts 1,232,599 The 1-1/4 million pounds of chromium salts used for wood preser- vation in 1940 were no doubt considerably exceeded in 1941. With chromium salts, the situat zinc chloride for dependence must be plac chromium ores. As a result, the amounts may consume and the uses and allocations are under very strict control by the G-ove national defense uses receive highest pri are largely eliminated. The increase in plants in 1941 over 1940, in the; face of tributable to the fact that salt treatmen ion is quite different than with ed almost entirely upon imported of chromium ore that refineries of chromium and chromium chemicals rnment. Naturally, the most urgent ority ratings and nondefense uses chromium salts used by wood-preserving these restrictions, is possibly at- ts in 1941 were considered mainly lumbers underlined in parentheses refer to list of references at the end of this paper. R1284 -4- for high-priority national .defense structures. A prediction by the writers of what to expect in 1942 with regard to the chromate supply would be sheer guesswork. In addition to the chemicals named above, sodium fluoride, sodium arsenate, and dinitrophenol are necessary ingredients in Wolman salts. Copper sulphate constitutes 50 percent of Celcure preservative. Of those chemicals, dinitrophenol and sodium fluoride are under close control but the supplies of all have been low for some time and their availability for wood preservation in 1942 will be so largely determined by needs for other uses that it cannot be predicted by the writers. Other Preservatives Should be Considered Although an acute preservative shortage does not appear certain, treating plant operators and users of treated wood will be unwise if they ignore the possibility that economic and military developments may change the entire picture. During 1918 to 1921, for example, when the supply of creosote was limited, there was plenty of zinc chloride available and the amount consumed per year rose from 26 million pounds in 1917 to more than 51 million pounds in 1921. That is not likely to happen this time, however, because there are other substitutes for creosote that are much better than zinc chloride for outdoor use. During the 1918 to 1921 emergency, also, the use of creosote-petroleum solution began in earnest but this practice has proved so effective that it has increased greatly since that time. In considering what can be done in the event of inadequate supplies of creosote and of the customary salt preservatives, it is well to see what has already been done in some cases. One large consumer of creosote-petroleum solution, who customarily has used not less than 50 percent of creosote in the mixture has had to re- duce the percentage of creosote "ay half. In view of the uncertainty that this preservative will be sufficiently effective in the usual absorptions, he has increased the absorption from about 8 to 10 pounds per cu. ft. The net result of the change is that the ties receive only 2.5 lbs. of creosote per cu, ft., which is a net saving of at least 1.5 lb. of creosote per cu. ft. Ho general, shortage of petroleum for wood preservation is anticipated but there. may be temporary or local shortages due to transportation diffi- culties. Other consumers, who have for many years insisted on creosotes with -not over 20 percent (or 25 percent) distillation residue about 355°C. have been unable to secure adequate quantities of such oil and, for the. time being, have raised the acceptable limit to 30 percent or even higher. Steps are now being taken to amend the Federal specifications for creosote and for creosote-petroleum solutions, for the duration of the war, so as to permit residues up to 35 percent. In general, a 5 percent increase in residue above 355°C, should increase the yield of creosote from tar by about the same percentage, which is important in a time of shortage. R1284 •5- The consumers referred to felt that they had good reasons for their former preference for a high percentage of creosote in their creosote- petroleum solutions and for relatively low residue creosote. The changes made do not constitute an abandonment of their former preferences hut merely a realistic attitude and a logical conformance to the requirements of an emer- gency. Their emergency preservatives are still good preservatives, even though they may be less desirable in some respects than their preferred pre- servatives, to which they will probably return when that becomes practicable. Treating practices, wood species, and the availability of suitable materials vary considerably throughout the United States and the supply of usable preservatives may also vary at any place from month to month, For these reasons, it is not to be expected that any one material can serve as the universal substitute when supplies of creosote or preferred salt pre- servatives fail. It is desirable, therefore, for both plant operators and users of creosoted wood to study the various possible substitutes and thus to have several to choose from, according to local availability of materials and the needs of the job to be done. The following discussion of preservatives and processes is presented in the hope that it will be usoful in that connec- tion. Toxic 'Oils Other Than Creosote Certain toxic oils other than coal-tar creosote are available to the wood-preserving industry. Some have been tested in service so that their degree of effectiveness is reasonably well established; others are still unproven and their use is attended with greater uncertainty as to re- sults. In either event, they should receive careful consideration. Chlorinated phenols . — Solutions of polychlorinated phenols in petroleum solvents have been attracting attention for some years as pros- pective competitors of both creosote and salt treatments. The most promi- nent of the group in the last few years has been pentachlorphenol but tetra- chlorphenol end 2-chlororthophenylphenol have also received attention. All three have high toxicities to wood destroying fungi. Bateman and Baechlor (4) report killing points of 0.0C2 against the fungus "Madison 517" for penta- and tetrachlorphenol. Carswell and Hatfield (6) reported a killing point of 0.006 for pentachlorphenol and Hatfield (10) reported 0.009 to 0.01 for 2-chlororthophenylphenol. These toxicity values are not strictly comparable because of some differences in methods. They also cannot be compared directly with creosote toxicities for the latter vary widely, according to the character of the creosote. The toxicity of penta- and tetrachlorphenol, however, appears to be from 10 to 100 times that of coal- tar creosote, depending upon the creosote and the toxicity values used for comparison. Even when diluted to 5 percent concentrations, the toxicities, of the 3 chlorinated phenols appear to be equal to or greater than the toxicities of the coal-tar creosotes in common use. From the standpoint of toxicity then, 5 percent solutions of these chemicals appear suitable for wood preservation when used in sufficient absorptions. R1284 -6- Toxicity alone is, of course, no assurance of preservative effec- tiveness since permanence, as measured by chemical stability, volatility, and leachability in water, is equally important. In these respects, penta- chlorphenol is reported (7) to be highly satisfactory and the other two, from such other information as is thus far available, are also satisfactory. Laboratory tests, no matter how extensive, are not a final measure of the value of a preservative and wood preservers naturally want to know th results of service tests and actual use experience. Although solutions of these 3 chlorinated phenols have been used alone or in mixtures (20) for some years as preservatives for window sash and other millwork, very little information of value to the pressure treating industry is available from this experience. The absorptions and penetrations obtained in the 5-minute immersion treatment, which is the minimum standard treatment of the National Door Manufacturers Association -(20) , are rather low, the service conditions are usually not comparable to those for structural timbers, and service records on treated millwork are almost entirely lacking. Nevertheless, the results obtained appear to have been generally favorable. The manufacturers of the chlorinated phenols have numerous service tests under way which include treated saplings, 2 by 4-inch stakes, fence posts, and other forms of experimental material. Most of these are ground tests in which exposure is to decay and termites but some are salt water tests. Data from all these experiments are said to indicate a satisfactory degree of protection when suitable absorptions and penetrations were used but the data have not yet been published. A considerable quantity of lumber, land piles, poles, and other structural material has also been pres- sure treated with pentachlorphenol solutions, some for railroad use. Most of it has been installed too recently to furnish service data of value and no results have been made public on any of it. As early as 1931, 2 by 4-inch test specimens were treated by the Porest Products Laboratory with alcohol solutions and with petroleum solu- tions of tetrachlorphenol and installed in the Barro Colorado Island tests (12). Still other tests with pentachlorphenol solutions in 2 by 4-inch test specimens have been started by the Laboratory in cooperation with a preserva- tive company but too recently to provide useful information. In 1934 the Forest Products Laboratory started field tests on fence posts pressure treated with solutions of tetrachlorphenol in waste crank case oil and, since that date, has started other field tests in which solutions of tetrachlorphenol or pentachlorphenol have been used for fence post treatment. The results available to date from these various tests are given in table 2, together with some results with creosote and creosote-petroleum solutions in the same tests. Examination of table 2 shows that in most of the experiments, pentachlorphenol and tetrachlorphenol solutions are giving good results* Poorest results have been obtained when using alcohol as a solvent. Pence posts appear to be giving better results than 2 by 4-inch test specimens. This is true with creosote and creosote-petroleum solutions as well as with the chlorinated phenol solutions. It is probably due in part to the greater area exposed per unit volume in the smaller specimens, and partly to the severity of the expacure conditions. &L284 _ 7 „ These experiments do not settle the question of the relative effectiveness of creosote and solutions of chlorinated phenols nor do they determine the optimum concentration of solution or absorptions to be used with such solutions. They indicate, however, that petroleum solutions of pentachlorphenol and of tetrachlorphenol, when of sufficient concentration and retention, can give a high degree of protection against decay and termites and are promising materials to use when creosote is hard to get or is too ex- pensive. It is highly desirable that all other obtainable data from experi- ments and from use experience with those preservatives be made available as soon as possible* Pentachlorphenol and tetrachlorphenol are much more versatile pre- servatives than creosote for they are sold as technically pure solids or in concentrated solutions and can be carried in a variety of solvents. Where stronger solutions than 5 percent are required they can easily be made. Where practically colorless treatment or nonbleeding treatment is desired, it can be obtained by choosing suitable solvents. In using creosote-petroleum solutions with a low concentration of creosote, pentachlorphenol may be rdded to increase the toxicity. On the other hand, it is still wise to be cautious and conservative. There is a tendency for some promoters of pentachlorphenol preservatives to make extravagant claims for their products. Remarkable penetrating proper- ties-are most frequently claimed and the easily convinced are misled into believing that superficial treatments with pentachlorphenol solutions are equal to pressure treatments with creosote or accepted salt solutions. This idea is not new, of course, for similar claims are made for many proprietary preservatives, including several of the creosote or carbolineum type. In considering such claims, it should be remembered that pentachlorphenol and tetrachlorphenol by themselves do not penetrate wood and th: b the penetra- tions obtained with their solutions depend upon the solvents chosen and the treating conditions used. Petroleum solvents of very low viscosity do penetrate better than creosote, which has higher viscosity. Substantial absorptions and deep penetrations can often be obtained in easily treatable wood by merely soaking it for a day or more in low viscosity solutions of pentachlorphenol at atmospheric temperatures. Rather surprising results can also.be obtained with creosote under the same conditions. There is no known practical solvent, however, that penetrates deeply and quickly into wood that is resistant to penetration. The cheap byproduct petroleum oils of the fuel oil type ordinarily have viscosities as high as creosote, or higher, and cannot be expected to excel creosote in penetrating properties. The cost of pentachlorphenol will undoubtedly have much to do with its ability to compete with creosote in the 'future but, under present ab- normal conditions, availability may often be more important than cost. Penta- chlorphenol solutions appear to be as freely available now as creosote and at competitive costs but the situation can be changed at any time by priority orders. Por this reason, it cannot safely be predicted that pentachlor- phenol solutions will take up the slack if the creosote supply becomes in- adequate. After the war the supply of both creosote and pentachlorphenol should bo adoqua.te and cost will be a much more important factor. Creosote will still have the advantage of a century of successful use experience, but 2.1284 -8- Table 2. — Results of exposure tests on experimental material pressure treated by the Forest Products Laboratory with tetrachlorphenol and pentachlorphenol solutions Form of test material : Location of : test : Numbe r : of :pieces : in : test : rTeservative :Concentra- : tion of : preserva- : tive in : solution ; Average : absorption : Date .stalled .Length . of : serv- : ice : when . last in- specte< : Condition at last, : Inspection :Barro Colorado : Island : S :Tetrachlor- : phenol in : alcohol : Percent : 1.3 :Lb.per cu.ft . :1931 . Years ': 6 2*l+-inch pine stakes :0.3S (dry : chemical ) .6 destroyed in 4 : years. All des- : troyed in 6 years 2x4-- inch pine stakes :Barro Colorado : Island 7 :Tetrachlor- : phenol in : alcohol ': 2.6 :0.75 (dry : chemical) = 1931 10 .All but 1 des- : troyed in 7 : years 2x4-inch pine stakes :Barro Colorado : Island 7 :Tetrachlor- : phenol in : pstroleum : 5-0 .7-1 (solu- : tion) Il931 5 .7 destroyed in : 5 years 2xU-inch pine stakes :Barro Colorado : Island : S :Tetrachlor- : phenol in : petroleum 1 5-0 •13. S (solu- : ticn) = 1931 10 .7555 sound. . 12.5? destroyed 2x4-inoh pine stakes :Barro Colorado : Island : S :Tetrachlor- : phenol in : petroleum : 9.1 17.3 Uolu- : tion) Il931 10 .25? sound, 62.5?5 : destroyed, 50? : destroyed after : 5 years 2x4-inch pine stakes Barro Colorado Island : S :Tetraohlor- : phenol in : petroleum 9-1 lllt.l (solu- • tion) I1931 10 .87.552 sound. None destroyed 2x4— inch pine stakes Barro Colorado Island : & :Coal-tar creosote " 7.0 :1931 10 .12.5% sound, 62.5$ destroyed 2xU-inch pine stakes Barro Colorado Island : S : Coal-tar : creosote " 13.6 ■1931 10 .75? sound, . 12.5? destroyed 2x4- inch pine stakes Barro Colorado Island : S :50^ creosote, : $0% petroleum " 7-1 1931 10 37.5? sound, 37-5* destroyed 2x4-inch pine stakes Barro Colorado Island ': S 50# creosote, 50# petroleum "- lit. 5 1931 10 10M sound Round northern whitw-cedar fence posts Wisconsin . 20 Tetrachlor- phenol in waste crank- case oil 2.S6 6.5 (solu- tion) 193 1 * 7 100)? sound Round northern white-cedar fence posts Wisconsin 33 Tetrachlor- phenol in waste crar.k- case oil 2.9 S.5 (solu- tion) 1936 It 100? sound Round aspen posts Wisconsin 22 Tetrachlor- phenol ii waste crank- case oil 2-9 8.2 (solu- tion) 1936 1* 100? sound Riund aspen posts Wisconsin 10 Tetrachlor- phenol in waste crank- case oil 2.9 7.5 (solu- tion) 1936 5 100)8 sound Round jack pine posts Wisconsin 30 Tetrachlor- phenol in waste crank- case oil 2.75 5-7 (solu- tion) 1936 5 100? sound ack : posts : iVisconsin 5* Tetrachlor- phenol in waste crank- case oil 2.75 5.3 (solu- tion) 193 1 * 7 93? sound (ft ok : pine posts ; Wisconsin S7 Tetrachlor- phenol in : waste crank- oase oil 5.0 5.7 (solu- tion) 193t 6 to 7 99? sound mthern pine posts : Mississippi 99 Tetrachlor- : phenol in : waste orank- : case oil 2.9 7.1 (solu- tion) 1936-37 ! it 97? sound Round southern: ; StS : liississippl 100 Tetrachlor- phenol in : waste crank- : case oil 4.8 5.S (solu- tion) 1936-37. 1* 100? sound ■uthem: pine posts : Mississippi 99 Pentachlor- : phenol in : waste crank- . case oil 4.S 6.7 (solu- tion) 1936-371 It 99? sound Round southern: pine poi Mississippi 99 Pentachlor- phenol In i waste crank- ; case oil i 3.0 , 6.U 1936-37'. h 99? sound juthem: poata : Mississippi 99 : Coal-tar : creosote i -- 6.0 1936-37; k 100? sound ■ : ilississippi 100 : Coal-tar creo-: sote 50#, : waste crank- : case oi 5- 1 * 1936-37; k 99? sound . - Waste crank- : case oil : : 7-6 1936-37 J k 27? sound, U5? destroyed if experience with pentachlorphenol solutions continues to bo favorable and their cost per unit of timber treated is lower than that cf creosote, their use is likely to grow at the expense of creosote. V/ater-gas tar . — Most of the water-gas tar now being produced is used in road tars. The exact amount used in wood preservation, including that which is distilled to produce a creosote and that which is blended with coal- tar creosote, is difficult to ascertain. Water-gas tar varies greatly in viscosity according to the oil from which it is made, as well as the condi- tions of manufacture. Much of it is too viscous to be suitable for wood preservation but satisfactory absorptions and penetrations may be obtained with the less viscous tars. Service tests (2, 24) show that water-gas tar is a very good preservative when properly applied and is well worth consider- ing as a substitute for coal-tar creosote for land use. Low-te.iipera.ture tars and creosotes . — Low-tenperature coal-tar creosotes differ in chemical composition from high-temperature coal-tar creo- sotes as shown by pronounced differences in a number of properties, such as specific gravity of fractions, sulfonation residue, tar-acid content, and naphthalene content. Some of them have given very good results in service tests (2) and a paper by Dr. Re id (22) reports interesting ana favorable laboratory data about another. The total amount of these oils available for wood preservation is not large and apparently it is being used mainly in mixture with high- temperature coal-tar creosote. The tar produced by the Curran-Knowles process is sometimes re- ferred to as a low-temperature tar, but in most of its characteristics it lies between a high- temperature and a true low-temperature coal tar. The few service tests that have been started on the tar alone have not yet reached a stage where conclusions may be drawn. At present all of it is said to be sold for wood-preservation purposes and is used undistilled and adxed with coal-tar creosote. It apparently finds fa^or for this purpose because of its low viscosity, distillation residue, and benzol-insoluble content. The low-temperature coal tars and Curran-Knowles tars produced in the United States result for the most part from the manufacture of smoke- less domestic fuel. Certain indications point to an increased use of these processes in the future, but because of priorities on building materials any great expansion in any of them is not to be expected for some time. The total production of these materials probably comprises less than 5 percent of the coal -tar creosote used annually. Lignite coal-tar creosote has been used by one railroad company for some years, in mixture with coal-tar creosote and petroleum oil. The limited service data thus far available (24) fail to show that lignite- tar creosote is equal to coal-tar creosote, but in certain regions and under certain con- ditions its use may well be an economy. The Portland Gas and Coke Company, in carbonizing petroleum oils for the- manufacture of municipal gas, produces an oil tar from which a R1284 -9- creosote may be distilled. Some tests on this creosote (23) by the block method indicate that it has considerable promise as a wood preservative. Aromatic petroleum oils . — The importance that petroleum oils used as diluents of creosote have assumed in the wood-preserving industry is well .recognized and the possibility of extending our supplies of creosote by re- ducing the creosote percentage in these mixtures has been mentioned. In ad- dition to furnishing tfoe inert oils that are now being used as diluents or solvents, the petroleum refining industry might be a source of toxic oils. This field, which has been sporadically explored in the past, is now of re- newed interest because of changes in conditions. As a general rule, straight distillate oils from petroleum are too insoluble to kill wood-destroyin^ fungi growing either en agar or wood. They usually exert some retarding effect and within a given boiling range the tendency to be toxic increases with the aromaticity of the oil.' By the use of certain preferential solvents, it is possible to extract from petroleum oils, constituents that will kill wood- destroying fungi. In cracking heavy petroleum oils to produce gasoline, the un- converted residual oils tend to increase in aromaticity. In applying the different basic cracking processes and their variations to different crudes, a large number of different oils of varied properties are produced by the petroleum industry. Certain refining processes other than cracking also tend to increase the aromaticity of oils. The yields of some of these oils are small on a percentage basis but, because of the tremendous volume of oil processed, the volumes of the byproducts are large by standards of the wood- preserving industry. Determinations of toxicity have been made on a number of samples of aromatic petroleum oils. As a general rule, they are not quite soluble enough to kill the organism growing on agar, but their inherent toxicity is shown by the fact that very small amounts permit only a very feeble growth. It is possible that these oils would show fairly good preservative properties in service and it might be possible to fortify them with relatively small amounts of toxic chemicals or creosote. Some preliminary tests have indicated that mixtures of creosote and aromatic petroleum oils may be more toxic than equivalent mixtures of creosote and petroleum oils now being used in the wood- preserving industry. It is hoped that these studies may be continued. One patented process (2l) is said to produce an oil from petroleum residues that is practically identical with coal-tar creosote so far as all ordinary tests show. If this can be substantiated, it will be of great interest, but thus far, little if any progress has been made towards commer- cial production of the oil. Wood-tar creosotes . — Although wood-tar creosotes have been avail- able in small quantities for many years, they have never been used extensively in pressure treatments. This has been due in part to the relatively limited -i -antities produced and, to some degree perhaps, to lack of sufficient stan- dardization. For the most part, these products appear to have been sold for nonpresnure use although there have been substantial exceptions. R12B4 -10- No very positive statements can be made about the effectiveness of wood-tar creosotes because of the differences in character of the products obtained fron different sources. The test data available indicate a consider- able degree of effectiveness but do not show that the v/ood-tar creosotes can be safely assumed to be equal to coal-tar creosotes. Red oak ties with an absorption of about 10 lbs. of wood-tar creosote per cu. ft. , in test for 21 years at Madison, Wisconsin, (2) will probably have an average life of about 20 years or more. Another group of hardwood ties in the same test that are mostly red oak and were treated with 9 to 10 lbs. of a 50-50 mixture oi wood- tar creosote and coal-tar creosote per cu. ft. v/ill have an average life of about 27 years or more. In the Forest Service fence posfc study in Mississippi (24) southern pine fence posts pressure treated with 6.6 lbs. of a wood-tar creosote per cu. ft. were showing more deterioration at the end of 3 years than similar treatments v/ith coal-tar creosote or a 50-50 mixture of coal-tar creosote and waste crank-case oil. In the Barro Colorado Island tests also (13) the specimens treated with wood-tar creosote are not standing up quite so well as those treated with coal-tar creosote. While the evidence fails to indicate that wood-tar creosotes are equal to coal-tar creosotes in ability to prevent decay and termite attack, the wood-tar creosotes do have considerable protective value. They have been used occasionally in the past in mixture with coal-tar creosote, as an accommodation to the wood-tar producer. Opportunities may now occur when this would be of advantage to both the producer and the user of the wood-tar creosote, and thus serve to extend the supply of coal-tar creosote. When such mixtures are contemplated, it will be advisable to consider the quality of the wood-tar creosote very carefully and, if possible, have it meet a definite specification. High acidity and high volatility in the wood-tar product should be avoided. Tests should also be made to assure that the oils used will mix satisfactorily without producing a sludge during the mixing operation or subsequent heating. Naphthenates . — Copper naphthenate and, probably, some of the other metallic naphthenates have considerable value as wood preservatives. Their use, up to the present time has been confined almost exclusively to surface applications which necessarily has limited their effectiveness and, until very recently, they were sold only in proprietary preservatives. One such preservative has been in use for many years in Europe, particularly in Denmark and in England, but the sale of naphthenate preservatives in the United States appears to have only begun during the last <± or 5 years. The growing interest in the naphthenates as preservatives appears to arise from the increasing quantities of naphthenic acids being produced as byproducts of the petroleum industry and the urge to find markets for them. The effectiveness of the naphthenates as wood preservatives has not received adequate study and no data are available as to the absorptions that should be injected for best results. It is possible that petroleum solutions of copper naphthenate could be made to protect wood as well as creosote does but it remains to be seen what solution concentrations and absorptions would be necessary and whether they would be economically R1284 -11- feasible. The fragmentary information available fro:.; various minor studies of copper naphthenate give favorable indications with regard to toxicity, permanence, and field tests. Prush treatments with a naphthenate preserv - tive arc said to have given only mediocre protection but apparently satis- factory protection from substantial absorptions injected by pressure. Field tests have been started recently by the Forest Products Laboratory, in cooperation with a producer of naphthenates, in which surface and impregna- tion treatments in a variety of absorptions arc being compared but these tests will yield no results in time for the present emergency. It see.-s doubtful that copper naphthenate will be sufficiently plentiful or cheap in the near future to be of much use as a substitute for creosote in pressure treatments. At prices comparative with current creosote prices, however, copper naphthenate solutions would warrant serious considera- tion. They appear sufficiently promising to justify extensive experimental use even now, despite their present cost. Preservative Salt — Oil Treatments Card treatment . — The Card treatment with a mixture of creosote and zinc chloride solution,' which was used extensively for tie treatment prior to 1934, was originally developed as a means of economizing on cost by re- ducing the amount of creosote used per tie. It does not offer much of value in the present situation, however, because equal or greater saving of creo- sote can 'be accomplished by using creosote-petroleu.i solutions, which are more desirable and more effective than the Card mixture. Zinc chloride-petroleum treatments . — Several types of zinc chloride- petroleum treatments have been described by E. R. Poller (5). Since these treatments use no creosote, they have a distinct advantage over Card mixtures from the standpoint of creosote economy. Service records are not sufficiently comprehensive or complete to permit an exact comparison between these two treatments but it seems quite possible that the petroleum combination would at least equal the Card mixture in effectiveness ^nd, because of the larger amount of petroleum oil injected per cu. ft., it night exceed the Card treat- ment. The effectiveness of the zinc chloride-petroleum treatment can undoubtedly be varied considerably, according to the absorptions of zinc chloride and petroleum used. A disadvantage of the zinc chloride-petroleum treatment is that it is a two-movement process and, therefore, more complicated and expensive than a one-movement process. Another disadvantage is the uncertainty as to the zinc chloride supply but this is true of practically all preservatives. Combination salt and oil treatments are not limited to zinc chloride but are possible with all accepted salt preservatives. Zinc chloride has the advantage over the other salt preservatives for this purpose, however, in that its solutions can be heated to over 200 F. without causing undesirable chemical reactions that reduce the concentration of preservative in the solution. This permits a high-temperature Rueping P1234 -12- treatnent with the zinc chloride solution, followed by a vacuum that evaporates some of the surplus -water, and then the immediate application of the oil treat- nent. With preservative salts that cannot be heated to such high temperatures, less water is removed during the vacuum period and the wet wood is lesr suit- able for the oil treatnent. Air seasoning between the salt treatnent and the oil treatnent will, of course, renove the excess water and put the wood in excellent condition to receive a good oil treatnent. This net hod is practica- ble with all the salt preservatives but the extra handling for seasoning and retreatnent is expensive and the tine required for the seasoning prolongs the processing period. In short, petroleun-salt treatnent can be applied in various ways, gives. longer life than straight salt treatnent, and avoids the use of creo- sote but has the disadvantage of being a two-movement treatnent. Other Preservative Salts The preservative salts thus far mentioned, namely, Celcure, chronated zinc chloride, Tanalith, zinc chloride, and ZMA, are not the only water-borne, salt- type, preservatives that can be used. Various others are known that have nore or less value oven though not so extensively used. Their cost, availability, priority limitations, and other considerations greatly Unit the ability of these materials to relieve the shortage of . other preservatives, nevertheless they nay in individual cases be very practical and ocononical to use and they should not be overlooked. Among then are the .following: Aczol is a proprietary preservative solution containing copper and zinc salts and ammonia. In one test (13) Aczol in heavy absorptions has given excellent results but in another test (2) it has not done so well. It seems unlikely that Aczol can be made available in sufficient quantity to contribute nuch to the relief of the shortage of creosote and other pre- servatives or that it will be economical to use in the high absorptions that appear to be desirable for a high degree of protection. Nevertheless, Aczol undoubtedly has preservative value and should receive consideration when it is available in an emergency. Borax has been shown (4) to have greater toxicity to fungi than zinc chloride and in a service test on 200 rod oak ties (2) with absorptions of 0.24 and 0.59 lbs. of borax per cu. ft., only about 4. percent have been removed for decay in 13 years. A group of 31 southern yellow pine fence posts pressure treated with an average 1.05 lbs. of borax per cu. ft. shows about 55 percent removals after 15 years service in Wisconsin. The Barro Colorado Island tests (13) indicate that borax treated wood in contact with the ground does not have high resistance to termites but it cannot be deter- mined from these tests whether the lack of resistance was due to leaching or to low inherent toxicity to termites. Until that question is settled, it would not be wise to depend upon borax for protection against termites, even where there is no opportunity for leaching. H1284 -13- Borax is rather strongly alkaline in reaction and nay possibly have some effect on the strength of the wood. The service tests thus far fail to indicate any adverse effect on strength but they are no proof that there is no such effect. So far as fence posts and similar products arc concerned there seems little to fear, but for timbers that must carry heavy loads some caution should be exercised. Bateman and Baechler (4) suggested that a mixture of borax and boric acid, being neutral in reaction, would be less likely to damage the wood (and paint) and would still bo nearly as toxic to fungi as the straight borax solution. Only one service test of such a mixture appears to have been started (24). One hundred southern yellow pine fence posts pressure treated with an average absorption of 0.9 lbs. of 50-50 borax-boric acid per cu. ft. and placed in test on the Harrison Experimental Forest in Mississippi showed no removals at the end of 4 years but 4 percent were showing evidence of termite attack. In normal times, borax is cheap and plentiful and the borax-boric acid mixture should be competitive in cost with other salt preservatives. Under present conditions the demand for borax for other uses is heavy end its availability for wood preservation is questionable. This situation may change, however, for there is plenty of borax in the ground and increasing the refining capacity could provide all the borax and boric acid needed for all uses. Whether that will be accomplished in the near future we are unable to predict. Chcmonite is a proprietary copper-arsenic-ammonia wood preserva- tive (8) that has found some commercial use on the Pacific Coast. Its continued availability obviously will depend upon the availability of the chemicals of which it is composed. The preservative has not been fully evaluated or generally accepted nor is it yet certain that the optimum ab- sorptions have been arrived at. Nevertheless it appears to be doing very well in unreported service tests and there can be no doubt that Chcmonite preservative, when properly applied, can give a considerable degree of pro- tection against decay and termites to wood in contact with the ground. It has not yet reached the' stage of development that would justify its general acceptance as a so-called "standard" preservative because it has not had sufficiently extensive use over a long period of time. The results thi t have been obtained to date, however, are very promising and justify favorable consideration. It certainly should not be ignored for land use where it is economically available and where it may often be a practical alternate to turn to in emergency. Its suitability for marine use is open to question and has not been sufficiently demonstrated to justify our recommending it for the protection of piles in salt water. Minerali zed-cell -preser vative.— This is a proprietary preservative said to contain xtSfleaio. trioxide, zinc sulphate, and copper sulphate, all of which are known to have preservative value. It stands to reason, there- fore, that wood properly impregnated with a sufficient absorption of this mixture will have its decay and termite resistance increased. Since the preservative has found some use for the treatment of piles in Pacific R1284 -14- Northwest for a number of years, it should be possible to obtain service records that indicate the magnitude of its effectiveness but none are known to have been published. It is not reasonable to suppose that a. preservative of this character would give much protection to piles in salt water and the published (18) and unpublished information available recommends strongly against its use for that purpose. It nay, however, compare well with various other salt preservatives for land use and may properly receive consideration for such use when available in an emergency. Miscellaneous salts . — There are, of course, other salts, which either should have or are known to have more or less preservative value, that have not been used to any significant extent for commercial pressure treatments, if at all. Such salts, however, are unlikely to be freely avail- able now. About all that need be said about them now is that they could probably be used to advantage if they were available at reasonable cost. Among these are mercuric chloride, which is a powerful preservative but expensive, corrosive and poisonous; Boliden salt (9.); greensalt (Ascu) (12. IE); sodium fluoride; copper sulphate; arsenates and other salts of nickel; and a variety of others that have been included in various field experiments but not commercialized as wood preservatives. Processes To the operators of commercial pressure treating plants, there would seldom, if ever, be any advantage in turning to a nonpressure treatment. For the user of pressure treated wood, however, certain nonpressure treat- ments may be useful in an emergency when the customary pressure treated material is unavailable. Similarly, users of butt-creosoted poles, in facing a creosote shortage may have to turn to other methods as well as preservatives. Standing pole treatments . — Standing poles that have begun to de- cay at the ground line can have their service life materially prolonged by ground line treatment if the upper parts are in good condition and the decay at the ground line has not progressed too far. Several types of such treat- ments have developed during the last 10 or 15 years. Their relative effective- ness and economy has not been worked out but enough information has been obtained to indicate that a number of them have merit under normal economic conditions and that they can extend the life of poles several years. In the present emergency they may prove very useful to. public utilities in the event of a shortage of their preferred creosoted poles and with the necessity of making their standing poles last longer. These various ground line treatments have been described in publi- cations or are being actively promoted by their proprietors and it seems un- necessary to describe them individually here. Several of these treating methods use coal-tar creosote, including the charring and spraying method ( 11 ) , the "sand-collar" method developed by the Hydro-Electric Power Commission of Ontario (15) , the "impregnated sawdust collar" method (16), pouring creosote in the earth around the poles, and no doubt others. They, of course, use E1284 -15- less creosote per pole than is required to treat a new pole and in that way econonize on creosote. Still greater creosote economy is obtainable, however, by using pole base treatments that contain less creosote, such as the Osmose and Pfister treatments, or the Anaconda arsenic paste method, which uses no creosote. The Osmose method . — The Osmose method is a nonpressure method of treating lumber, poles, mine timbers, posts, and similar materials in the green condition and without the use of creosote. Its economy and effective- ness in comparison with "standard" preservatives and treatments remain to be worked out. No doubt they vary widely under different circumstances. The fluoride-chromate- arsenic-phenol preservative that is applied to the surface of the wood in paste form does penetrate appreciably under favorable circum- stancec, however, particularly in sapwood. Such treatment should have effec- tiveness in proportion to the absorption and penetration obtained and, in pine posts and timbers, this has been shown to be considerable. The nature of the preservative is such that the treatment cannot be expected to have the effectiveness of creosote impregnation in material that must be in contact with the soil or water but in emergencies, and particularly in places ' remote from pressure treating plants, the Osmose treatment warrants consideration. The chemicals of which the Osmose preservatives are made, however, like most other preservative. chemicals, are available in limited quantities and this restricts the extent to which treatment by this method can be expanded. The steeping process . — Merely soaking green or dry wood in a heated or unhcated water solution of preservative salt for a week or two, is ouch more efficacious than is commonly supposed. Its use, of course, depends on the availability of preservative salts and its value is primarily in places remote from pressure treating plants or for quantities of material too email •to interest such plants. When mercuric chloride is applied by this method, remarkable results are sometimes obtained and very good results have been obtained with zinc chloride and sodium fluoride, as is shown in the 1942 report of the Committee on Post Service Records (l_). Oil-salt combination for poles .— A pole treating method that has had some use in recent years is to apply full length pressure treatment with a salt preservative then, with or without subsequent seasoning, to apply a hot- a .nd-cold bath creosote treatment to the butts. This serves to economize on creosote as well as to provide a pole that is "clean" above the ground line. The process appears to have considerable merit and for some uses it justifies careful consideration. . There are various other methods of treatment that might be mention- ed (ll_,3) including several of the Boucherie type, that can sometimes be used in an emergency or under special conditions, but it seems unnecessary to catalogue them here. £1284 -16- Summary The foregoing discussion has forecast that the amount of creosote produced in 1942 for wood preservation from domestic sources will considerably exceed the domestic production in' 1941 but that we enter 1942 with such low stocks that the amount of domestic creosote available for use in 194:' not exceed that of 1941. If the authorities decide that the military needs per- mit, enough foreign oil can be imported to supply all requirements not net by domestic production. This is strictly a problem of war-time economics, however, and what the decision will be only those dn control can determine. The preservative salts in cor.rn.on use or that might be used are all of more or less limited availability. Zinc chlori-de seems least likely to be seriously restricted but not one of them will be available in unlimited quantities and it should cause no surprise if any or all of them should be less available for wood preservation in 1942 than in 1941. The only toxic preservative that, at present, see..:s likely to be more available in 1942 than in 1941 is pentachlorphenol. Extenders for creo- sote and solvents for pentachlorphenol, either in the form of ordinary fuel oils or aromatic byproducts of petroleum cracking processes seem likely to be available in any quantity that may be needed for wood preservation. Among the substitute materials or practices that seem most pro. .us- ing today for immediate use if needed for large volume treating requirements are the following: use higher percentages of petroleum or tar in creosote solutions, raise the limits on the percentage of creosote distillation residue above 355° C. where such limits have been -set up,, and use penta- chlorphenol in petroleum solutions. Obviously the practicability of these and other methods will vary considerably in different places and circumstances and may be upset at any time by new developments. There is also the possibil- ity that the need for them may be largely avoided by a reduction in the amount of timber to be treated. The results of adversity are not always evil and not infrequently the things we are forced to do against our will have unexpectedly beneficial results. The research for substitutes should broaden the knowledge of. us all and we may find that some of the substitute materials or methods will prove economical and desirable for continued and even expanding use under the highly competitive conditions that we all expect to exist after the present emergency is over. References Cited (1) American Wood-Preservers' Association Report, pf Committee, Poles, ITon- Pressure Treatment, A.W.P.A, Proc. 1942. (2) American Wood-Preservers 1 Association Report .of Committee on Tie Service Records, A.W.P.A. Proc. 1941 (and earlier).. R1284 _ 17 _ (3) Anon. Methods of applying wood preservatives, Forest Products Labora- tory Mimeograph R154, 20 p. , 1940. (4) Batcman, Ernest and R. K. Baechler, "So:.ie toxicity data end their practical significance", A. W.P.A. Proc. , 1937, p. 91-104. (5) Boiler, E. R. , "Zinc chloride-petroleum treatment for ties," A. V/.P.A. Proc. 1940, 361-376. (6) Car swell, T. S. , and Ira Hatfield, "Pentachlorphenol for wood preserva- tion," Ind. and Eng. Chen. 31, 1431-35 (tfov. 1939). (2) Carswell, T. S. , and H. K. Has on, "Properties and uses of pentachlor- phenol," Ind. and Eng. Chen. 30, 622-26 (Juno, 1938). (8) Gordon, Aaron, U.S. patent 2,149,284, March 7, 1939 and earlier patents. (9_) Hager, Bror, "Preservation of wood with the Bolidcn preservative com- posed of difficultly soluble arsenates," A. T ' T .P.A. Proc. 1941, 45-53. (10) Hatfield, Ira, "Toxicity in relation to the position and number of chlorine atoms in certain chlorinated benzene derivatives," A. *'. ? .P.A. Proc., 1935, 57-66. (11) Hunt, G-.M. and G. A, Garratt, "Wood Preservation," 450 pages, McGraw- Hill Book Co. , 1938. (12) Hunt, G.M. and T. E. Snyder, "An international termite exposure tost," A.W.P.A. Proc. 1932, 282-297. (13) "An international termite ex- posure test," results reported annually in A, W. P. A. ProcJ.930 to date. (14) Helphunstine, R. K. Jr., "Quantity of wood treated and preservatives used in the United States in 1940," A. V/.P.A. Proc. 1941, <±10~432. (.15) Hydro-Electric Power Commission of Ontario, "Ground line preservation of wood poles," The bulletin, June, 1939. (l_6) Johnson, R. A. , "Preservation of wooden poles, impregnated sawdust collar method," Electrical Engineer and Merchandiser (Australia) April 15, 1940, 17. (17) Lumsden, G. , and A. K. Hearn, "Greensalt treatment of poles, "A. V/.P.A, Proc. 1942. (18) MacDonald, T. H. , "The place of treated timber in highway construction", A. V/.P.A, Proc. 1939, 154-159. (19) McMahon, 17. , C.M.Hill, and F.C. Koch, "Greensalt — a new preservative for wood", A.W.P.A. Proc. 1942. R1284 -18- (20) National Door Manufacturers Association, "Minimum standards for ..mil- work preservatives" (mimeograph) May 21, 1938. (21) Putt, J. W. , U.S. patent 2,207,552, Jul;/ 9, 1940. (22) Reid, J. J., "A study of several products of Disco-type, low-temperature coal tar as wood preservatives," A. W.P. A. proc. 1942, (23) Voorhies, Glenn, "Oil-tar creosote for wood preservation," Oregon State College, Bulletin Series No. 13, June 1940. (24) Wirka, R. M. , " Comparison of preservatives in Mississippi fence post study," A. W.P. A, Proc. 1941, 365-378. R1284 _19_ UNIVERSITY OF FLORIDA 3 1262 08866 6077