INDUSTRIAL AND ENGINEERING CHEMISTRY
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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
A
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 : rLTC‘nt 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. Effect of Time of Fat-Liquoring BIGURE 5 .
EFITCT OF 111‘3 OP FAT-LIQUORING ON m s m i a u T m x w OIL M L ~ I T H ~ R
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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.
