136 KRYPTOPHANIC ACID. 



of kreatinine ; it will produce a white curdy precipitate, 

 which is soon transformed into needles. 



6. Add to an aqueous neutral solution of zinc 

 chloride some kreatinine solution ; a crystalline preci- 

 pitate is immediately produced in the form of warty 

 grains. 2(C 4 H 7 N 3 0)Zn01 2 . 



Kryptophanic acid, C 5 H 9 N0 5 , or C 10 H 18 N 2 10 . 1. 

 Evaporate fresh urine to one third ; mix with excess 

 of milk of lime or baryta, allow to stand a few hours 

 and filter : acidify the filtrate with acetic acid, 

 evaporate to a syrup, and set aside to crystallise. 

 Separate the crystals by draining and pressure from 

 the mother liquor, add to the latter five times its 

 volume of alcohol of 90%, shake well, allow to stand 

 for five minutes, pour off the liquid and wash the 

 precipitate with a little more alcohol. Warm the 

 sticky deposit to drive off the adhering alcohol, dis- 

 solve in a small quantity of water and filter. To the 

 filtrate add twice its bulk of saturated solution of lead 

 acetate, filter from the dark brown precipitate, mix the 

 filtrate with three volumes of 90 % alcohol, wash with 

 alcohol the nearly white precipitate of lead Jcrypto- 

 phanate, lastly wash with a little absolute alcohol, dry 

 at 100 C., and weigh. 



2. Mix with water to a thin cream, and for every 

 100 parts of the dry salt add an equal weight of sul- 

 phuric acid containing 25% of H 2 S0 4 . After standing 

 for some time, with frequent agitation, filter and test a 

 portion of the filtrate for sulphuric acid; if any be 

 present precipitate it out exactly with baryta water, 



