744 NITROGENOUS FATS. [APP. 



soluble in cold, exceedingly so in hot alcohol ; sether dissolves it freely 

 though in less quantities, as also do chloroform, fats, benzol, carbon di- 

 sulphide, &c. It is often obtained from its alcoholic solution, by eva- 

 poration, in the form of oily drops. It swells up in water and in this 

 state yields a flocculent precipitate with sodium chloride. 



Lecithin is easily decomposed : not only does this decomposition set 

 in at 70 C., but the solutions, if merely allowed to stand at the ordinary 

 temperature, acquire an acid reaction, and the substance is decomposed. 

 Acids and alkalis, of course, effect this much more rapidly. If heated 

 with baryta water it is completely decomposed, the products being 

 neurin, glycerinphosphoric acid, and baric stearate. This may be thus 

 represented : 



Lecithin. Stearic acid. Glyceringaosphoric 



3H 2 = 20 18 H 38 3 + 3 H 9 P0 6 + C 5 H 15 N0 2 . 

 When treated in an sethereal solution with dilute sulphuric acid, it is 

 merely split up into neurin and distearyl-glycerinphosphoric acid. Hence 

 Diakonow l regards lecithin as the distearyl-glycerinphosphate of neurin, 

 two atoms of hydrogen in the glycerinphosphoric acid being replaced by 

 the radicle of stearic acid. It appears also that there probably exist 

 other analogous compounds in which the radicles of oleic and palmitic 

 acids take part. 



Preparation. Usually from the yolk of egg, where it occurs in union 

 with vitellin. Its isolation is complicated, and the reader is referred to 

 Hoppe-Seyler*. 



Glycerinphosphoric acid. C 3 H 9 P0 6 . 



Occurs as a product of the decomposition of lecithin, and hence is 

 found in those tissues and fluids in which this latter is present : in 

 leukhsemia the urine is said to contain this substance. It has not been 

 obtained in the solid form. It has been produced synthetically by 

 heating glycerin and glacial phosphoric acid ; it may be regarded as 

 formed by the union of one molecule of glycerin with one of phosphoric 

 acid, with elimination of one molecule of water. It is a dibasic acid ; 

 its salts with barium and calcium are insoluble in alcohol, soluble in cold 

 water. Solutions of its salts are precipitated by lead acetate. 



Protagon. (0 lt50 H 3a8 N 5 P0 33 ?) 



A crystalline body, containing nitrogen and phosphorus, obtained by 

 Liebreich 3 from the brain substance and regarded by him as its principal 



1 Hoppe-Seyler's Med. Chem. Untersuch, Heft. n. (1867), S. 221, Heft. in. (1868), 

 3. 405. Centralb. f. d. med. Wiss. (1868), Nr. 1. 7 u. 28. 

 3 Med. Chem. Untersuch. Heft. n. (1867), S. 215. 

 3 Ann. d. Chem. u. Pharm. Bd. 134, S. 29. 



