APPENDIX. 



255 



stant weight. Treat the residue in the flask for some hours at room temperature with 

 50 cc of benzol. Filter through a small paper into a tared dish, evaporate l<> drynesH 

 and dry to constant weight, at 100 ( ., thus obtaining the amount of ralTein. 



Determine the theobromin by KunzeV* method as follows: 



Add to tlu filter paper 150 cc of water, enough ammonia water to make the solution 

 slightly alkaline, and an excess of decinonnal silver nitrate solution. Boil to half 

 the original volume, add 75 cc of water and repeat the boiling. If the solution still 

 contains the slightest trace of free ammonia repeat the process of adding water and 

 boiling until the solution is perfectly neutral. Filter off the insoluble silver theo- 

 bromin compound and wash with hot water. In the filtrate determine the excess oi 

 silver nitrate^ by Volhard's method as directed under "III. Inorganic Plant Con- 

 stituents," 6, page 23. 



8. Other Nitrogenous Substances. 



Add the percentages of nitrogen present as theobromin and as caffein,c subtract 

 the sum from the percentage of total nitrogen and multiply the remainder by G.25. 



9. Crude Fiber.d 



Proceed as directed under "VI. General Methods," 11, page 56, except that the 

 fiber is filtered and weighed on a paper. 



10. Crude Starch. 



Weigh 4 grains 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 a 11 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 residue to the 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. In the case of sweetened products the filtrate should measure at 

 least 500 cc. Conduct the hydrolysis of the residue as directed for "Starch" under 

 "VI. General Methods," 8 (a), page 53, except that after neutralizing with sodium 

 hydroxid, add 5 cc of basic lead acetate solution/ 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 determine reducing matters in 25 cc of the filtrate as directed 

 under "VI. General Methods," for "Reducing Sugars," 7 (b), (2), page 49. Deter- 

 mine copper by the direct weighing of the cuprous oxid, 7 (c), (6), page 53. 



11. Pure Starch. 



Remove fat and sugar from 4 grams of the material if unsweetened, or 10 grams if 

 sweetened, as directed under "Crude Starch." Carefully wash the wet residue into a 

 beaker with 100 cc of water, heat over asbestos to boiling with, constant stirring, and 



aZts. anal. Chem., 1894, 33 : 1. 



6 1 cc of decinonnal silver nitrate solution is equivalent to 0.01802 gram of theobromin. 



cThe percentage of theobromin multiplied by 0.311 and that of caffein multiplied by 0.289 give the 

 respective percentages of nitrogen. 



din the analyses of commercial cocoa and other finely ground, pulverized cocoa products, the residue 

 after fat extraction may be used directly for fiber determination. If, however, the material is at all 

 granular, it must be reduced to an impalpable powder, otherwise the results will be much too high. 

 The pulverization may be satisfactorily performed by grinding with ether as hereinafter described 

 under "10. Crude Starch," removing the extracted residue with the hot 1.25 per cent sulphuric-acid 

 solution. 



Copper-reducing matters by direct acid hydrolysis. 



/Prepared as directed under "VI. General Methods," 6 (b), U). page 40. 



