118 PUBLIC HEALTH CHEMISTRY 



31 to 34 C. (Distinguish from coco-nut oil, from Cocos 

 nucifera, a tropical palm. Melting point 20 to 26 C.) 



Ash. Ignite 5 grm. in a platinum dish at a low red heat. 

 If red, examine for iron. Is about 3 per cent in raw cocoa 

 (rock cocoa), and 5 per cent in commercial varieties. 

 Contains about I per cent of phosphoric anhydride, but 

 this varies. 



Soluble Ash is not determined from the ash but from the 

 soluble extract. It should not fall below 2 per cent. 



Soluble Extract (cold water extract). Five grm. of the 

 sample are rubbed up in a mortar with 250 c.c. of cold 

 water until a smooth mixture results. Shake at intervals, 

 and allow to stand over night. Filter 50 c.c. (= I gram, 

 of sample) and evaporate to a constant weight (dryness). 

 Should not exceed 18 per cent. Any material excess is 

 probably due to added sugar. This residue is now ignited 

 at a gentle heat, cooled, and weighed, and the result called 

 the " soluble ash " (better, the ext. ash). 



Theobromine is allied to caffeine, being a dimethylxan- 

 thin, and like it is not precipitated by potassic mercuric 

 iodide, or by I in KI. Estimate by treating with petroleum 

 ether ; remove latter on water-bath ; extract with alcohol ; 

 evaporate alcohol ; add water, and clarify with PbAc ; 

 remove lead with H 2 S, and extract with chloroform. 

 Amount varies from 1-3 to 1-7 per cent. Theobromine 

 contains 31-1 per cent of nitrogen. 



Proteins. Estimated approximately by Kjeldahl process. 

 Deduct N due to theobromine and x by 6-25. Averages 

 2-2 per cent except where proteins added (plasmon cocoa) . 



Starch. Cocoa contains about 10 per cent of natural 

 starch. The granules are small and round and are easily 

 distinguished from any likely to be added as an 

 adulterant. 



Sugar is determined by extracting 10 grm. in a filter- 

 paper cylinder in a Soxhlet to remove the fat. 

 Dry and extract with alcohol, which dissolves the sugar 

 and other matters. Remove latter as before, boil for ten 

 minutes with 2 per cent HC1, neutralize, and estimate the 

 invert sugar by Pavy's process. The residue contains the 

 starch. Boil for six hours with 200 c.c. of 2 per cent 



