80 



Caffein method. It is suggested that the caffein iodin precipitate does not form 

 immediately and that the low results are due to filtering and titrating the solution too 

 quickly. Other work indicates that after the iodin is added the flask should be 

 allowed to stand in an ice chest overnight before titrating. 



Much better results can be secured by Gomberg's original method for caffein, 

 iven in the Journal of the American Chemical Society (1896, 18: 331), and modified 



Extract 2 grams some time with four portions of water, cool, and make to 1,000 cc. 

 Treat 500 cc "with 15 cc of saturated lead acetate solution, let settle, filter, remove 

 lead with hydrogen sulphid, boil off excess of hydrogen sulphid, divide filtrate into 

 two parts, concentrate each to 50 cc, add 0.2 cc of concentrated hydrochloric acid to 

 one and 6.5 cc of acetic acid to the other, cool to 15 C., add 20 cc of tenth-normal 

 iodid solution, stopper flask, and let stand in ice two hours, filter on a gooch. Caffein 

 does not precipitate unless mineral acid is present, so the acetic acid portion shows 

 if any other materials are present which would precipitate with the iodin solution. 

 If any absorption of iodin is found in the acetic portion, it must be deducted from 

 the titration containing mineral acid. The difference represents the iodin used up 

 in the formation of the periodid of caffein: 1 cc of tenth-normal iodin equals 0.00485 

 gram of caffein. Using this method, 0.78 per cent of caffein was obtained from the 

 coffee reported. 



Krauch method for extract in tea. The bulk of sample (20 grams) makes complete 

 removal of water-soluble substances almost impossible. The absorption of water by 

 large filter paper and on surface of flask during weighing is also a serious objection to 

 the method. If sample is ground, filter paper is clogged and filtration prevented. 



Doolittle and Woodruff method. Care should be used to keep the entire sample in 

 the boiling liquid during extraction or low results will be obtained. Any loss of water 

 by evaporation should be replaced. 



NOTES BY REFEREE. 



The discrepancy in the results obtained by the two analysts with the Trillich and 

 Gockel method is due principally to the fact that Mr. Woodruff used 5 cc of basic lead 

 acetate in the precipitation instead of 1 cc, as prescribed in the method. Determina- 

 tions made by the referee on the same sample gave 10.08 per cent where 2 cc of basic 

 lead acetate was used and 12.04 per cent when 4 cc was used. The lower results 

 obtained by Mr. Woodruff in the caffein estimation may have been due to the greater 

 volume of solution in which the caffein periodid was precipitated, he using a volume 

 of 100 to 150 cc, while the referee employed a volume of 20 cc. Experiments made 

 by Mr. W. C. Taylor in the writer's laboratory have shown the necessity for concen- 

 trating the caffein solution to small bulk. 



The determinations made of extract in tea by the referee convinced him of the 

 great superiority of the Doolittle and Woodruff modification over the Krauch method 

 as regards convenience, time, and liability to error. 



COCOA PRODUCTS. 



The following results were obtained from the collaborating chemists on cocoa 

 products: 



Cooperative work on cocoa products. 



