ALKALOIDS. 405 



with strong nitric acid it forms a yellow liquid which, after evapora- 

 tion, assumes a purplish color when moistened and carefully heated 

 with water of ammonia. 



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. 



Theobromine, C 7 H 8 N 4 O 2 (Dimethyl-xanihine). 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 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 3 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. 



Piperin, C 17 H 19 NO 3 . This compound is found in black and white 

 pepper. While it is isomorphous with morphine, it differs widely 

 from it in all its properties. It can hardly be called an alkaloid, as 

 it has no alkaline reaction, is but feebly basic and does not show the 

 general alkaloidal reactions. It forms colorless, or pale yellowish 

 crystals which are, when first put in the mouth, almost tasteless, but 

 produce on prolonged contact a sharp biting sensation. 



Piperin dissolves in concentrated sulphuric acid with a dark blood- 

 red color, which disappears on dilution with water. Treated with 

 nitric acid it turns rapidly orange, then red. 



Ptomaines (Putrefactive or cadaveric alkaloids). It has been 

 known for a long time that vegetable, and more especially animal 

 matter, when in a state of decomposition (putrefaction) acts generally 

 as a poison, both when taken as food or when injected under the skin. 

 Though many attempts had been made to isolate the poisonous pro- 

 ducts, this was not accomplished successfully until the years 1873 to 

 1876, by Francesco Selmi, of Italy. He demonstrated that a great 

 number of basic substances can be extracted from putrid matter by 

 treating it successively with ether, chloroform, amyl alcohol, and 



