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THE JOURNAL O F INDUSTRIAL AND ENGINEERING CHEMISTRY
that an excess of the highly toxic, low-boiling constituents would be necessary under service conditions to act as a reserve to compensate for leaching and evaporation. Table 5 gives a list of five commercial preservatives sent to this laboratory to be tested. Sample IV proved to be the most toxic substance we have yet tested. Probably its toxicity lies for the most part in the 23.8 per cent of dinitrophenol which it contains. Falckl found that it required less than 0.02 per cent of o-nitrophenol and less than 0.01 per cent of either p-nitrophenol or the sodium salt of the 2,4-dinitrophenol to kill Coniophora cerebella, which is a very destructive wooddestroying fungus. The remaining oils, with the exception of Sample I, which is a carbolineum of somewhat higher boiling point than the
62 1
TABLE&-TOXICITY OF VARIOUS COMMERCIAL PRESERVATIVES Sp. gr. PRESERVATIVE DESCRIPTION R t 38“ C. Anthrasota, A brownish-black mild liquid sold as Sample 3353 a high-boiling coal-tar distillate; 1.115 15.1% .. distils below 275O C. Grade I Sold as a high-boiling coal-taro disCreosote, tillate; 18% distils below 275 1.089 Samole 3352 Wood A brown oily liquid. sold as highPreservative, boiling nonvolatil; coal-tar oils . Conservo” and other preservative salts Mykantin, A brownish green paste soluble in Sample 3393 water: 23.8% dinitrophenol Preservol A black pungent wood distillate conSample 3557 taining 4.1% acid (calc. as acetic). 1.058 88.5% distils below 265” C.; wate; 10.870
. ..
.. ..
Killing Point Per cent Between O.9and 1.1 Between 0 . 2 and 0 . 3 Between 0.1 and 0.15 Below 0 . 0 1 Between 0.land 0 2
Grade I creosote, proved highly toxic. The results on the coal-tar products are plotted on the curve in Plate IV.
The Toxicity of Various Fractions and Combinations of Fractions of CoalTar Creosote to Wood-Destroying Fungi 2 ~ s
By Henry Schmitz and Sanford M. Zeller SCHOOL OF FORESTRY, UNIVERSITY OF
IDAHO,
MOSCOW,
I D A H O , AND
Considerable work has been done in the past to determine the toxicity to wood-destroying fungi of various fractions of coal-tar creosote and many other wood preservatives. However, much of this work is of little or no practical importance for either of two reasons: First, wood impregnated with the creosote was not used as the substrate, and, second, the minimum percentages of single fractions are of little or no concern, but rather a combination of certain fractions with the elimination of certain others. That is, the most probable result which obtains after a creosoted timber is exposed to natural weather conditions is the evaporation and leaching of the lighter and more soluble parts of the mixture. Among the later workers in this field are Humphrey and Fleming,4 who determined the toxic point of some fractions of creosote, but who used single fractions in all cases and combined them with nutrient agar, conditions in no way comparable with those in actual practice. The literature regarding this line of investigation has been sufficiently reviewed in the paper just cited so that no review will be made here. The discrepancies between the so-called petridish method used by the above-mentioned writers and the conditions met with in treated timbers are obvious. In the first place, the emulsion which is formed when creosote and agar are thoroughly mixed is by no means permanent, and, even in very rapid cooling of the agar after the emulsion has been formed, it is quite probable that the individual minute droplets have coalesced to form droplets of considerable size resulting in a more or less irregular mixture varying from globules of the insoluble portions of the creosote to nutrient agar containing varying proportions of the water-soluble portions of the creosote mixture. I n the second place, it is a well-known fact5 that the toxicity of a certain substance may be altered materially by the presence of other substances. This may be particularly true where there are 1 Alfred Moller, “Die Merulius-faule des Bauholzes.” I n “Hausschwammforschungen,” 6 (1912), 365. 1 Received March 21, 1921 8 This work was begun in the Research Laboratories of the Missouri Botanical Garden and completed in the Laboratory of Forest Products, School of Forestry, University of Idaho. Thanks are due t o the Missouri Botanical Garden for the privileges of the laboratories, and t o Doctor Hermann von Schrenk for suggestions. a “The Toxicity t o Fungi of Various Oils and Salts, Particularly Those Used in Wood Preservation,” U. S. Department of Agriculture, Bulletin 227 (1915), 1, Plates 1-3. 5 A Le Renard, “Influence du Milieu sur l a resistance d u Penicille crustuce aux substances toxiques,” Ann. s c i nul bot., [ 9 ] 16 (1912), 277.
OREGON AGRICULTURALCOLLEGE, CORVALLIS, OREGON
such complex relations as would exist between emulsions, colloids, electrolytes, and non-electrolytes, such as are found in a n emulsion of coal-tar creosote in nutrient agar. On the other hand, the use of impregnated wood as a culture medium for fungi causing wood decay offers no particular difficulty, and there is more valid reason than not why wood should be used in preference to synthetic media. It has seemed to the writers that sawdust, although not physically the same as solid wood, is the most appropriate medium for the culture of wood-destroying fungi in such studies as are presented here. METHODS In the present study, creosote (von Schrenk and Kammerer No. 3072) derived from coal tar was used. This oil, when analyzedl according to the method2 now standard in the American Railway Engineering Association, the American Wood Preservers’ Association, and the American Society for Testing Materials, gave the following results: Sample No. Sp. gr. a t 35” C. Water DISTILLATIO~N TEMPERATURE C. 210 235 270 315
3072 1.048 0.0 Per cent 3.6 32.4 23.8 16.9 15.4 7.9 7.5 1.038 1.100
FRACTIONATION-FOr the experimental work here recorded, the creosote was fractionated as follows: 1-Undistilled. 2-Fraction below 210’ C. 3-Fraction between 210’ and 235’ C. 4-Fraction between 235’ and 270’ C. &-Fraction between 270’ and 315’ C. 6-Fraction between 315’ and 355’ C. 7-Residue above 355’ C. S-Combination of all fractions, except 9-Combination of all fractions, except 10-Combination of all fractions, except 11-Combination of all fractions, except 12-Combination of all fractions, except 13-Combination of all fractions, except
below 210° C. between 210’ and 235’ between 235’ and 270° between 270° and 315’ between 315’ and 355’ residue above 355’ C.
C. C. C. C.
1 Thanks are due to Dr. A. L. Kammerer, Consulting Timber Engineer, St. Louis, for making this analysis and for fractionating thecreosote and combining the various fractions. 2 Proc. A m . Wood Pueseroers’ Assoc., 1917, 309.
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PmPmATioN OF MEDIA-A~~fractions and combinations of fractions were entirely soluble in 95 per cent ethyl alcohol, except the residue above 355" C. The following method was therefore employed: Twice the maximum concentration (calculated in weight of creosote to weight of airdried wood) of creosote was dissolved in 100 cc. of redistilled 95 per cent ethyl alcohol. One-half of this alcoholic solution was added slowly and with constant stirring to 20 g. of air-dried yellow poplar (Liriodendron tulipifera) sawdust in a large beaker. This amount of alcohol was just sufficient to saturate the sawdust 50 that no free liquid remained, and an evenly impregnated sawdust was obtained. The remaining 50 cc. of alcoholic solution were diluted to 100 cc. with alcohol, giving a concentration of creosote equal to one-half the former. This procedure was carried on throughout the range of concentrations used. The impregnated sawdust was spread out on dean glass plates for 24 hrs., in which time all of the alcohol had evaporated. The sawdust now weighed exactly 20 g. plus the weight of the creosote calculated for each dilution. Hence, no creosote was lost during the 24-hr. exposure to the air. Even had there been a little loss in weight, this would have been of no practical importance, since substances so volatile that they would be lost in so short a time would be of little or no practical importance in timber preservation. The same procedure was followed in the experiments where western white pine ( P i n u s monticola) sawdust was substituted for the yellow poplar sawdust. To prepare intermediate concentrations of creosote in sawdust, equal amounts of otherswere mixed. For example, a 3 per cent concentration was prepared from equal amounts of the 2 and 4 per cent material. I n some cases, however, it was also necessary to make a new series of dilutions. , As has been said, one fraction (the residue above 355" C.) was not entirely soluble in alcohol. I n this case, the same procedure was employed and the remaining insoluble substances were added proportionately by weight to the various I flasks. After the alcohol had evaporated, 3 g. of the impregnated sawdust were placed in each of four 8-02. bottles. Twenty cc. of distilled water were then added to each bottle containing the white pine, while 12 cc. of water were added to each of the flasks containing the tulip poplar sawdust. I n each case this amount of water was just sufficient to saturate the sawdust thoroughly without any free water remaining. STERILIZATIOS-The media were sterilized as follows : The bottles were tightly corked with suberin stoppers surrounded by heavy paraffined paper and placed in R rigid , wooden frame into which the corked bottles would fit tightly, so that there would be no possible chance of the corks blowing out or becoming loose while being autoclaved. All of the bottles were autoclaved for 20 min. at 20 lbs. pressure. Immediately after autoclaving, the corks were , removed and previously sterilized cotton plugs were substituted under sterile conditions to avoid all possible chances of contamination. The bottles were then ready for inoculation.. A check was run on this method of sterilization in order to determine whether any creosote was lost during the process of autoclaving. A series of culture bottles (not including the corks), prepared as above described and carefully weighed to the fourth decimal place before and after autoclaving, showed no loss in weight. PREPARATION O F CULTURES-The fungi used were Polyporus lucidus (Leys.) Fr. and Lenzites saepiaria Fr. Duplicates were prepared for each concentration of creosote. Three control sets were also prepared for each wood, one with natural sawdust, a second with sawdust treated with
Vol. 13, KO.7
alcohol a t the rate of 50 cc. per 20 g. of sawdust, and a third with sawdust treated with alcohol a t the rate of 100 cc. per 20 g. of sawdust. I n each case the alcohol was evaporated as previously described by spreading the sawdust on a glass plate and exposing the latter to the air for 24 hrs.
1 5
B E'
i3 1
1'
TOXICITY O F T H E VARIOUS FRACTIONS A N D COMBINATIONS O F FRACTIONS O F COAL-TAR CREOSOTE T o Lenszles saepiaraa AND Polyporus Luczdus
The culture bottles were inoculated by means of small squares of agar from plate cultures of the respective fungi. After inoculation, the bottles were incubated a t 28" C. until the sawdust in the control flasks was entirely permeated with the fungous mycelium. This required about 18 days in the case of Polyporus lucidus and about 25 days in the case of Lenzites saepiaria. Growth was also slower on the white pine sawdust than on the tulip poplar sawdust. The cultures were carefully examined with a hand lens to determine whether, and if so to what extent, the mycelium had permeated the sawdust. I n the foregoing curves the minimum toxic concentration expressed in per cent dry weight of the sawdust is shown on the abscissas. DISCUSSIONOF RESULTS The data are self-explanatory. The results indicate no toxic effects of any single distilled fraction or combination of fractions of the coal-tar creosote below a concentration of 1 per cent, calculated on the weight of air-dried sawdust. That is, there was no visible cessation of growth of either Lenbites saepiaria or Polyporus lucidus below a 1 per cent concentration. I n a majority of cases, the toxic point, which we have defined as the minimum percentage of the creosote which will completely inhibit the growth of the organisms, lies between 2 and 4 per cent. Because of the discrepancies between the two methods, as pointed out elsewhere in this paper, the results of our experiments are at variance with those obtained by Humphrey and F1eming.l This was to be expected, and a eomparison of the results could not be beneficial here because of the many factors which would naturally lead to differences in results. The comparison of the results of the two methods can only be left to their merits in practical application, and either one may be discarded if a preferable method is suggested for the testing of the toxicity of wood preservatives. From the data obtained, it is evident that Lenzites saepiaria is more resistant to greater concentrations of coal-tar creosote than is Polyporus lucidus. As would be expected, the percentage of creosote necessary to inhibit the growth of wooddestroying fungi varies with the wood. The two most toxic fractions are those which distil over between 235" and 270" C. and between 270" and 315" C. There is no great difference in the toxicity of any of the combinations of the various fractions except when the residue above 355" C. is omitted. Since this residue is toxic only in very high concentrations, its absence from the combination of the others would tend to increase their united toxicity.
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T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHELMISTRY
It may be argued that the computed percentages of creosote, calculated on the basis of dry weight of the sawdust, are not the actual values which should be taken into consideration because of the amount of water present during the growth of the organisms. However, we feel that there would be little in favor of such an argument when compared with actual practice. In commercial practice the amount of impregnation is calculated as pounds of creosote per cubic foot of wood, seasoned either before or during the process
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of impregnation. Thus, the percentage of creosote ultimately becomes a question of weight, depending upon the specific gravity of the wood. Moreover, in actual practice, impregnated timbers, such as railroad ties, may be placed under moisture conditions very favorable to the support of fungous growth. Under these conditions, moisture would be absorbed by the wood. The present experiments were attempts to imitate these natural conditions which are conducive to timber decay.
Nitrocellulose and Its Solutions as Applied to the Manufacture of Artificial Leather' By W.I(.Tucker HERCULES POWDERCo.,12 FORBES ST., WORCESTER, MASSACHUSETTS
Although nitrocellulose has been used in the manufacture of artificial leather for a good many years, very little has been printed which is of practical value to anyone wishing to make a study of the business. This has been due partly to the desire of those who have had practical experience to profit personally by their knowledge, and partly because many who have had the requisite experience have not been scientific men and have worked roughly by rule of thumb, being entirely unfamiliar with the underlying principles. The facts presented in this paper have long been known to scientific and practical men in the artificial leather business, but so far as I know have not been published, and are of interest to industrial chemists. VISCOSITY OF SOLUTIONS The first important point to be considered in the use of nitrocellulose for this purpose is Yiscosity. I n discussing the viscosity of nitrocotton it is always understood that reference is made to the viscosity of a 16-OZ.solution of nitrocotton in some solvent. This standard solution is made by dissolving 16 oz. of nitrocellulose in a gallon of solvent. A certain increase in volume occurs during this process so that the standard 16-021. solution contains somewhat less than 16 oz. of nitrocotton to the gallon of solution. For instance, in one of our standard solutions 16 oz. of nitrocotton added to 1 gal. of the mixture of solvents and non-solvents produced 1.965 gal. of solution, containing 12.2 per cent of nitrocotton. If the solution actually contained 16 oz. of nitrocellulose to the gallon the percentage would be 13 per cent. The viscosity of nitrocellulose is determined by noting the time taken for a steel ball five-sixteenths in. in diameter to drop through a 10-in. column of a 16-OZ.solution of the material in question. This would appear to be a simple method and one that could be used by any manufacturer. Unfortunately, a great deal of confusion occurs when customers order cotton specifying the viscosity by this method, because there is no standard solvent generally used for sucha test, and varying temperatures and the size of the container affect the result. In this laboratory we use a standard 16-OZ.solution (i. e., 16 02;. of cotton to the gallon of solvent), and the solvents are roughly 70 per cent ethyl acetate and 30 per cent benzene. A standard container, large enough in diameter to prevent any effects of friction from the displacement of the solution, is used, and the test is made a t 25" C. In general, this is the method used by large consumers and manufacturers of nitrocellulose to determine viscosity, and it is accurate enough, providing the mixture of solvents and the apparatus be standardized so that conditions are identical when the test is made by the manufacturer and could get together the data consumer. If this SOCIETY 1 Presented before t h e Section of Cellulose Chemistry a t t h e 61st Meeting of t h e American Chemical Society, Rochester, N. Y.,April 26 to 29, 1921.
required and standardize the method, a great service would be rendered to the industry, eliminating many unfortunate mistakes and misunderstandings. It may be noted here that most of the cotton used for the manufacturing of artificial leather is of low viscosity. The problem is to fix the required amount of cotton and other solids on a cloth base with the least loss of solvents. As the viscosity of the final solution as applied is fixed within rather narrow limits by the coating machine, and as the solution must be as inexpensive as possible, it is obvious that a cotton is desirable which will allow of the addition of a large amount of cheap non-solvent, such as benzene, and yet not bring the viscosity of the solution above the set limits (i. e., about 40 sec.). As the addition of non-solvents always increases the viscosity of a solution, the low viscosity cotton is logically the grade most suitable, since it will admit of the addition of the most non-solvent. Although the manufacture of nitrocellulose of various viscosities is too big a subject to enter into in this paper, the following generalities can be mentioned. A high viscosity cotton usually results from a high nitrogen content, or from a low temperature during nitration, while a high nitrating temperature or a long nitration results in a low viscosity product. The industry uses nitrocotton of three viscosities: low, from 5 to 20 sec.; medium, from 40 to 60 sec.; andhigh,from 100 to 2400 sec. The greatest demand is for a material of about 20 sec. The higher viscosities are generally used for blending purposes to bring the viscosity of a certain solution up to the required point. DEGREEOF NITRATION Roughly stated, the problem is to place a certain amount of nitrocotton on the surface of the cloth with the least waste of solvents. The second point to be considered is the conditions of nitration desirable in nitrocellulose to be used in the making of artificial leather. This is determined by the fact that varying degrees of nitration affect its solubility in the commonly used solvents. The nitrogen content of such a material averages about 12 per cent, although a range of from about 11.5 to 13 per cent is allowable. Roughly speaking, the lower the nitrogen content between these limits, the greater the solubility, and consequently the greater the amount of non-solvents which can be used in solutions. If the nitrogen content goes above or below these limits, the solubility of the nitrocellulose in the usual solvents decreases; less non-solvents can be used, and finally particles of cotton fail to go into solution, remaining suspended in the solution. STABILIZATION The third point to consider is the question of stabilization
