616 CONSIDERATION OF CARBON COMPOUNDS. 



Theobromine has been obtained from xanthine, C 5 H 4 N 4 O 2 (a base found in 

 animal liquids), by treating its lead compound with methyl-iodide, CH 8 I, when 

 lead iodide and dimethyl-xanthine are formed. By introducing a third methyl 

 group into the molecule of theobromine trimethyl-xanthine, i. e., caffeine or 

 theine is formed. These facts show the close relationship between the active 

 principles of the vegetable substances used so extensively in the preparation 

 of the beverages, coffee, tea, and chocolate. And again, these principles show 

 a relationship to a series of substances (such as xanthine, uric acid, and others) 

 which are found in animal fluids. 



Caffeine, Caffeina, C 8 H 10 N 4 O 2 .H 2 O or C 5 H(CH 3 ) 3 N 4 O 2 .H 2 O = 

 210.64 (Trimethyl-xanthine, Theine, Guaranine), occurs in coffee, tea, 

 Paraguay tea, and a few other plants. It forms fleecy masses of long, 

 flexible, silky needles, which are soluble in about 45 parts of water 

 and in 53 parts of alcohol ; it has a slightly bitter taste and a neutral 

 reaction. 



Caffeine is dissolved by sulphuric acid without color ; when evapo- 

 rated to dryness with hydrochloric acid and a little potassium chlorate 

 the mass assumes a purple color on holding it over ammonia-water. 



Two volumes of a saturated solution of caffeine in water mixed 

 with one volume of mercuric chloride solution form after a short time 

 large crystals of caffeine-mercuric chloride. 



Oitrated caffeine (U. S. P.) is obtained by adding caffeine to a solu- 

 tion of citric acid and evaporating the mixture to dryness. 



Theobromine, C 7 H 8 N 4 O 2 (Dimethyl-xanthine^). Found in the seeds 

 of Theobroma cacao, a tree growing in the tropics. It is white, crys- 

 talline, sparingly soluble in cold water, alcohol, and ether, volatilizes 

 without decomposition at 290 C. (554 F.), has a neutral reaction, 

 but forms with acids well-defined salts. 



Theobromine sodium salicylate, C 7 H 7 N 4 O 2 .Na -f C 7 H 5 O 3 .Na (Diure- 

 tin), is a double salt of theobromine-sodium and sodium salicylate. It is 

 obtained by dissolving in water molecular proportions of sodium hydroxide, 

 theobromine, and sodium salicylate, and evaporating the solution to dryness. 

 It is a white powder, containing 50 per cent, of theobromine, readily soluble in 

 water, and easily decomposed by exposure to carbon dioxide or by acids. It is 

 incompatible with acids, bicarbonates, borates, phosphates, ferric salts, chloral, 

 etc. Its effects are like those of theobromine, but it has the advantage of 

 greater solubility. 



Unclassified alkaloids. 



Physostigmine, C 15 H 21 N 3 O 2 (Eserine). Found in the seeds of 

 Physostigma venenosum (Calabar bean). The pure alkaloid does not 

 crystallize well, is almost tasteless, and assumes gradually a reddish 

 tint. The sulphate and salicylate are official. Both are white or 

 yellowish-white crystalline powders, which have a bitter taste. The 

 sulphate is readily, the salicylate sparingly soluble in water. 



