78 



acid than benzole acid. In fact, the antiseptic properties of a saturated solution of 

 cinnamic acid are so slight that this substance would probably not serve as a preserv- 

 ative for foods. 



A method for the separation of benzoic acid and cinnamic acid by precipitation of 

 the latter with manganous salts a was tried unsuccessfully by Mr. Dunbar, who was 

 unable to secure a precipitation of either benzoate or cinnamate of manganese in 

 dilute solution. As is to be expected, Mohler's and Peter's reaction also give the 

 same end reaction in the presence of cinnamic acid." 



REPORT ON TEA, COFFEE, AND COCOA. 

 By A. G. WOODMAN, Associate Referee. 



The work of the referee for the past year has been limited to a study of methods for 

 the determination of caffein and caffetannic acid in coffee, extract in tea, crude fiber 

 and starch in chocolate, and sugars in milk chocolate. Twenty-two samples were 

 prepared and sent out to those who had expressed a willingness to collaborate, ten on 

 tea and coffee and twelve on cocoa products. These were accompanied by the 

 following directions and a letter of transmittal : 



CAFFETANNIC ACID. 



(a) Krug's method. Proceed as directed in Bui. 107,- p. 155. (Note that the formula 

 for lead caffetannate should be Pb 3 (Ci 5 H 15 O 8 ) 2 as in Bui. 107, Rev.) Save the filtrate 

 for the determination of caffein. After weighing the lead caffetannate determine its 

 lead content as follows: Digest with aqua regia, add sulphuric acid, heat to fumes, 

 cool, dilute, add alcohol, settle, filter, ignite, and weigh as lead sulphate. Calculate 

 as per cent of lead . 



(6) Method of Trillich and Gockel.b Boil 3 grams of coffee one-half hour with water, 

 filter, and repeat this treatment on the residue three times. The united filtrates are 

 made up to 1,000 cc. To 400 cc add 1 cc of basic lead acetate solution and allow to 

 stand overnight. Filter, wash, decompose the precipitate with sulphuretted hydro- 

 gen, filter from lead sulphid, evaporate to dryness, and weigh. 



CAFFEIN. 



In the filtrate from the lead caffetannate precipitate the lead with hydrogen sulphid, 

 filter, and remove the excess of hydrogen sulphid by boiling, concentrating the solu- 

 tion, if necessary, to about 100 to 150 cc. Add tenth-normal potassium iodid solution 

 of iodin in excess, filter through a little glass wool and determine the excess of iodin 

 with tenth-normal sodium thiosulphate. 



1 cc tenth-normal iodin equals 0.00485 gram caffein. c 



EXTRACT IN TEA. 



(a) Follow the provisional method as described in Bui. 107, p. 149. 



(6) Follow the method proposed by Doolittle and Woodruff (Bui. 105, p. 48). 



CRUDE FIBER (SAMPLE A). 



Proceed as directed in Bui. 107 under "VI. General Methods," 11, page 56, except 

 that the fiber is filtered and weighed on a paper. The sample should be pulverized by 

 grinding with ether as described in the succeeding paragraph. 



CRUDE STARCH (COPPER-REDUCING MATTERS BY DIRECT ACID HYDROLYSIS), SAMPLE A. 



Weigh 4 grams of the material if unsweetened, or 10 grams if sweetened, into a small 

 wedgewood mortar, add 25 cc of ether and grind with a pestle. After the coarser 

 material has settled decant off the ether together with the fine suspended matter on 



Scoville, Amer. J. Pharm., 1907, 79 [12]: 549-551. 



&Zts. Nahr. Genussm., 1898, 101. 



cGomberg: J. Amer. Chem. Soc., 1896, 18: 331. 



