CHEjmSTRY. 525 



water f< ir 2 iiiiimtes and dried gave no crystals of thein ])y this metho<l. The method 

 was also used witii siitisfactory results in testing coffee jirains, both green and roasted, 

 coffee leaves, kola nut, and guarana, and mate lea\es. 



The synthesis of indigo, J. M. Matthews {Jour. Hoc. Clu^m. Jud., 20 {1901), 

 Xo. i;, ])/>. ■'>■'> l-'i'>'>). — The methods for the preparation of artificial indigo and the 

 intluence of this manufacture U])(in the ontjuit of the natural product. 



The relative leather-forming value of the different tanning materials; 

 their speed of tanning and weight giving, with notes on the quality, J. YorL 

 an<l K. W. (tRIKfitii (./o»/-. ,S'oc. CIhui. ImL, M [1001), Xo. 5, pp. 4.^G-4S6). — This 

 article gives the results of a research carried out at Herold's Institute, London, under 

 the direction and support of the Leather Sellers Company. The authors made a 

 series of experiments to determine whether the hide-powder method of tannin 

 analysis can be relied upon for giving the tanning value of an extract, and whether 

 the results so olitained are borne out in practice. The test was carried outasfollows: 

 A large excess of tanning liquor of known strength was used with a given weight of 

 hide powder. The leather thus obtained w'as weighed and the amount of nitrogen 

 present in the leather determined by the Kjeldahl method. The weight of leather 

 which should have been produced was calculated from the weight of the hide powder 

 used ; and by analysi.« the amount of soluble matter absorbed from the liquor was 

 determined. The work covered a period of 2 years and represents many determi- 

 nations. The results, the authors claim, go to prove that, within the ordinary experi- 

 mental error, the hide-powder method is an accurate representation of the leather- 

 forming (juality of a tanning material. The excess of tannin makes no practical 

 difference in the result except to increase weight, and throughout the work the 

 results are proportionate. A number of tables are submitted showing, among other 

 things, the amount of leather oljtained'from a definite amount of sul)stance and the 

 percentage gain in weight in leathers made with the various tanning materials. 



Among the technical points brought out are the leather-forming and the weight- 

 giving values of the various extracts tested, the color given to the leather, the quality 

 of the product, its imperviousness to water, and its strength. 



Report to the International Association of Leather Trade Chemists on 

 results of comparative experiments with Freiberg hide powder, J. Paessler 

 {Li'(l('nnarkt,2 {1901), Xo. 1 ; abs. in Jour. Soc. ('hem. lad., 20 {1901), Xo. 4, P- 395).— 

 This hide powder, prepared according to Cerych's prescription, was sent out together 

 with samples of oakwood extract, quebracho extract (pasty and solid), and valonia, 

 to 6 chemists. The object sought was to determine whether the results obtained by 

 the same analyst with the different hide powders correspond and whether the mean 

 values obtained by different analysts agree. 



Only the non-tannin figures are given, and the results show that the differences 

 between maximum and minimum results of the same analyst are not important. 

 The differences between the results of different analysts with the quebracho extract 

 are not imj)ortant, but are somewhat greater with oakwood extract and valonia. 

 The differences appear to be due largely to the different ways of packing the filter. 



The conclusion is reached that the Freiljerg hide powder is very suitable f(jr tan- 

 nin analysis, and it is recommended that the filter be so packed that the quantity of 

 filtrate recjuired will come through in aljout 2 hours. 



Comparison of the international filter-tube method and the oflB.cial hide- 

 power method, H. W. Wiley and W. H. Krug {Leather Manufacturer, 12, pp. 9-10; 

 libs, in Jour. Ainer. Chem. Soc, 23 {1901), Xo. 6, Rev., p. 107). — In a comparison of 

 the 2 methods with various tanning extracts it was found that the filter method gave 

 lower non-tannins and corre.«i)(jndingly higher tannins than the official method. 



Comparative hide-powder tests, W. H. Krig {Leathn- Manufacturer, 12, pp. 

 10-11; abs. in Jour. Amer. Chem. Soc, 23 {1901), Xo. 6, Her., p. 107). — Tests were 



16275— No. 6—02 3 



