79 



a I L cm, blue ribbon, S. and S. paper. Repeat this treatment until no more coarse 

 material remains. After the ether has evaporated from the filter, transfer the fat-free 

 iv- id in- t<> th> mortar by means of a jet of cold water and rub to an even paste, filtering 

 on the paper previously employed. Repeat this process until all sugar is removed. 

 1 ii i lie case >f sweetened products the filtrate should measure at least 500 cc. Conduct 

 tin- hydn>ly-is of the residue as directed for "Starch" under "VI. General Methods," 

 8 (a), page 53, Bui. 107, Rev., except that after neutralizing with sodium hydroxid, 

 add "> cc of basic lead acetate solution (prepared as directed under "VI. General 

 Methods, " 6 (6), (1), page 40) before completing the volume to 250 cc. To 100 cc of 

 the filtrate add 1 cc of 60 per cent sulphuric acid, filter off the lead sulphate and deter- 

 in iii'- n -d iic in<4 matters in 25 cc of the filtrate as directed under "VI. General Methods, " 

 i ! Reducing Sugars, 7, (6), (2), page 49. Determine copper by the direct weighing of 

 cuprous oxid, 7, (c), (6), page 53. 



SUGARS (SAMPLE B). 



cmine tlie lactose and sucrose as described 'by Dubois.o 



Tin- amount of work requested was purposely made small in order that it should 

 not prove burdensome, but in spite of this results were received from only four chem- 

 i - 1 . two on cocoa products and two on tea and coffee. 



TEA AND COFFEE. 



The results on tea and coffee are shown in the following table: 

 Cooperative work on coffee and tea. 



COMMENT BY MR. WOODRUFF. 



nirthfxtfor caffetannic acid. (I) The water must be kept to constant volume 

 durin- thirty-*! \ houn' di-e-tion. 



I'nlrss u'n-ai can is used, the addition of lead acetate to the hot alcohol solution 

 will cause violent ebullition and partial loss of contents. A safety tube helps to 

 oven-., me this difficulty. 



(3) In deiennining the lead content of the caffetannate it is advisable to filter the 



annaf through a tared gooch. This will allow of digestion of contents in nitric 



acid and precipitation of th.- lead with sulphuric acid without using a filter paper the 



arbon of which does not completely oxidize and produces a blackening of the lead 



sulphate. The final w.-iirhini: of the sulphate should also be made in a gooch. 



a J. Amer. Chem. Soc., 1907, 29: 560. 



