ISDC‘STRI.4 L A N D ENGINEERING CHEMISTRY
February, 1928
Summary
The addition of sodium chloride, sodium carbonate, or trisodium phosphate to sodium hydroxide markedly decreases the killing time a t 50” and 60” C. The effects of equal weights of sodium chloride and sodium carbonate are approximately the same, whereas the trisodium phosphate is less efficient. As the concentration of salts added to the sodium hy-
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droxide is increased the killing time is decreased, but at a decreasing rate. It is suggested that the undissociated sodium hydroxide may be the agent which penetrates the cell. The addition of the various salts would increase the concentration of undissociated sodium hydroxide, or possibly decrease the solubility of the sodium hydroxide in the water phase which would tend to force the sodium hydroxide into the bacterial phase of the suspension. In either case the effect would be to increase the death rate of the bacteria.
Some Preliminary Experiments on Fat-Liquoring’ Henry B. Merrill A. F. GALLUN & SONSCo.,MILWAUKEE, Wis.
T SOME stage between tanning and finishing all leather undergoes a treatment designed to incorporate in the tanned skin a certain amount of oil. Light leathers are generally drummed with an emulsion of various animal or vegetable oils, the process being known as “fatliquoring.’’ If the operation is properly carried out, nearly all the oil in the fat-liquor is absorbed by the skins, the used liquor is nearly clear, and the skins themselves neither look nor feel greasy, in spite of containing up to 20 per cent of fats and oils. Almost no quantitative work has been done on the chemistry of fat-liquoring. Except that it has been recognized that a fat-liquor must be a fairly stable emulsion, almost nothing is known of the nature of the interaction of oil and leather, and of the variables which affect it. Most of the fatliquors in use are quite complex, containing numerous constituents in proportions which are juggled until a desired effect is obtained, after which the formula thus obtained is adhered to rigidly. Preliminary to any attempt to determine the function and laws governing the employment of the various constituents of practical fat-liquors, it is necessary to study in
A
Experimental Procedure
The fat-liquors employed contained nothing but water and a sulfonated neat’s-foot oil (H,O, 22.3; ash, 4.7; total oil, 73.0; SOa combined with oil, 3.4 per cent), plus borax or sodium carbonate to regulate the pH value. The leather employed was ordinary 1-bath chrome calf, taken after coloring but before fat-liquoring. Small strips of this leather were fat-liquored under controlled conditions and, after drying, were split into five layers on a skiving machine. Each split was analyzed for fat, and from the thickness of the several splits and their fat content the penetration of the oil into the skin was shown, as well as the total amount of oil taken up by the leather as a whole. The exact composition of the liquors and the time of fat-liquoring are given in connection with the figures. I n all cases the temperature was 40” C. a t the outset, and fell off but little during the course of the experiment. I n expressing the results obtained for distribution of oil in the skin, the percentage of fat (dry basis) in each layer was plotted as a function of the depth of the center of that layer below the grain surface in percentage of the total thickness of the skin.
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Fat-liquor: 2.5 grams sulfonated neat’s-foot oil; 0.25 gram borax in 50 cc. per 100 grams wet leather. Time: 2 hours
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hv. depth 2b belowrbmain : Pl‘ELnt 6b
Fat-liquor: sulfonated neat’s-foot oil and borax (10:l) in 50 cc. volume per 100 grams leather, Time: 2 hours
the simplest possible system the effect of such fundamental variables as ratio of oil to leather, concentration, time, and p H value upon the total quantity of oil absorbed and its & tribution in the leather. The results of such experiments me reported in this paper. 1 Pesented under the title “A Preliminary Study of Fat-Liquoring” before the Division of Leather and Gelatin Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 6 to IO, 1927.
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Fat-liquor: sulfonated neat’s-foot oil and borax (1O:l) in 50 cc. volume per 100 grams leather. Time: 2 hours.
Distribution of Oil-Effect
of Drying
h d be seen from Figure 1, the distribution of fat in Chrome leather is far from Uniform. The center contains no oil except the natural skin fat. Contrary to a widespread impression, penetration of the oil does not take place chiefly through the flesh side; if anything, more Oil is absorbed through the grain. No change occurs in the distribution of
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and that remaining in the liquor. The add i t i o n a l quantity of oil taken up, as the time of fat-liquoring is increased from 0.5 t o 4 h o u r s , is fixed chiefly in the g r a i n a n d flesh l a y e r s . (Figure 5 ) Penetration into the heart. of the skin is but little increased by lengthening the time of fatliquoring. Effect of pH Value
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of oil to skin the quantity of oil absorbed decreases as the fat1-0.5 houF 5- 7 l i q u o r is d i l u t e d . With 2.5 grams sulfonated neat’s-foot oil per 100 g r a m s w e t leather, the oil found in the whole skin after fat-liquoring dropped *v. ,‘epth be:ar erain : of t c b l from 4‘8 per cent to Fat-liquor: 2.5 grams sulfonated neat’s-foot 3.0 per cent as the oil; 0.25 gram borax in 50 cc. per 100 grams volume of the liquor wet leather was increased from 50 to 200 cc. The effect on the penetration was inconsiderable. BIGURE 5 .
EFITCT OF 111‘3 OP FAT-LIQUORING ON m s m i a u T m x OP OIL IN L ~ I T H ~ R
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Effect of Time of Fat-Liquoring
The quantity of oil taken up by the leather increases with time up to about 4 hours, and is thereafter constant (Figure 4); it is especially worth noting that in no case is all the oil present in the fat-liquor absorbed by the skin. Apparently an equilibrium is established between the oil in the leather
Vol. 20, No. 2 lI3LRB E .
AY. i e p t h below p a l n : percent o f t c l n l L d C b e c s
Fat-liquor: 2.5 grams sulfonated neat’s-foot oil X grams NarCOs in 50 cc. per 100 grams wet leather. Time: 2 hours
Two sets of experiments were performed I to determine the effect of hydrogen-ion concentration on the absorption and distribution of oil in leather. In the first, l e a t h e r samples of the same p H v a l u e were fatliquored with liquors containing increasing amounts of s o d i u m carbonate so that the final p H values of the liquors varied from 5.1 I , to 8.1. In the second, strips of leather were b r o u g h t t o equilibFat-liquor: 4.0 grams sulfonated neat’s-foot 0.4 gram borax in 100 cc. per 100 grams r i u m w i t h buffer oil; wet leather. Time: 2 hours solutions of p H values from 3 to 9, and were then fat-liquored with liquors all of which had the same p H value. Rather unexpectedly it was found that shifting the p H value, either of the liquor or of the leather, had no appreciable effect on the total quantity of oil taken up by the skin. Increasing p H value, however, greatly favors the penetration of oil into the skin; as the hydroxyl-ion concentration goes up, less and less oil is found in the surface layers, and more and more in the interior. (Figures 6 and 7) It is hoped that these preliminary experiments will prove useful both as disclosing a new method for studying the fatliquoring of leather and as indicating the type of results that may be expected from such studies.
German Synthetic Rubber Recent widespread newspaper publicity on German synthetic rubber was the result of an address made by Geheimrat von Weinberg of the German Dye Trust a t Frankfurt a/M, November 11, 1927, when he said that his organization “will be able t o produce easily the raw materials for synthesis of rubber and guttapercha by contact (or catalytic) synthesis,” and that application had been made for patents. Weinberg referred to raw materials for synthesis of rubber and not to the finished product. Fritz Hoffmann, of Breslau, is a t present identified with advanced research on synthetic rubber, and is believed to be engaged in producing synthetic isoprene from p-cresol and passing it through 8-methyladipic acid. During the war synthetic rubber was produced in Germany at the rate of probably 2500 tons annually, one-eighth of Germany’s normal consumption. A specia1plant was erected for the purpose a t Leverkusen, using calcium
carbide, but the process had to be abandoned after the war a s non-commercial. The synthetic rubber, moreover, decomposed in the air, and was not susceptible to vulcanization. However, Professor Hoffmann and his colleagues found the organic accelerators and refiners, the “Vulcacite,” capable not only of permitting vulcanization, but of rendering the product insensitive to light and air. These auxiliary products have since been of the utmost significance in processing natural rubber, as well as improving the quality of synthetic rubber. Whether research on synthetic rubber has been able to develop its elasticity in comparison with natural rubber seems doubtful. Undoubtedly the German Dye Trust has succeeded in cheapening the costs of the basic hydrocarbons, but natural rubber producers could lower prices without loss, and be strong competitors of a synthetic venture.
