54 HANDBOOK FOE BIO-CHEMICAL LABORATORY. 



monoclinic prisms containing 1 mol. water of crystallization, 

 which it loses when heated to 100 C. It dissolves in 74 

 parts water at the ordinary temperature, and in 9400 parts 

 absolute alcohol. It is insoluble in ether. Its watery solu- 

 tion is neutral in reaction, and has a bitter taste. Creatin 

 forms crystalline compounds with mineral acids and with 

 mercury. When heated with dilute mineral acids it is con- 

 verted into creatinin. It forms compounds with certain 

 metallic solutions. 



Creatinin, 



METHYL GUANLDHST HYDANTOIK. 



Preparation. 1. Evaporate several litres of urine to one 

 third or one quarter its volume, allow to cool, and decant liquid 

 from the precipitated salts, now precipitate with lead acetate 

 and filter. The excess of lead in the filtrate is removed by H 2 S 

 or soda solution; filter again, nearly neutralize with soda solu- 

 tion or acetic acid, heat to drive off H 2 S, and add a concentrat- 

 ed solution of mercuric chloride, which causes a precipitate. 

 Filter, suspend the precipitate in water and decompose it 

 with a current of H 2 S, and again filter. Decolorize the filtrate 

 with animal charcoal and evaporate to dryness. The mass is 

 recrystallized several times from strong alcohol. The creatinin 

 may be easily obtained pure from the creatinin hydrochloride 

 by treating with lead oxyhydrate and then crystallizing. 



2. One-half to one litre of urine is treated with baryta mix- 

 ture (1 vol. saturated Ba(N0 3 ) 2 solution and 2 vols. satu- 

 rated baryta-water) until no further precipitate is formed, 

 filtered, and the filtrate evaporated on the water-bath to a 

 thin syrup. This is mixed with an equal volume alcohol and 

 allowed to stand in a cool place for 24 hours ; the salts which 

 separate out are removed by filtration and the filtrate treated 



