454 CHEMISTRY OF THE TISSUES. 



Characters Crcatinine acts like a strong alkali, and forms 



double salts with metals. The most important is its compound 

 with zinc chloride. Add to an alcoholic or not very dilute 

 watery solution of creatine, a concentrated syrupy solution of 

 zinc chloride free from hydrochloric acid ; a precipitate of 

 wartv granules -will fall at once if the solution is concentrated ; 

 but it dilute, groups of needles will slowly form. The granules 

 ni under the microscope to consist of radiating groups 

 of fine needles. They are very sparingly soluble in cold water ; 

 more so in hot; insoluble in alcohol ; but very soluble in mine- 

 ral acids. 



This test is sufficient to distinguish creatinine. It is fur- 

 ther precipitated by silver nitrate, by mercuric chloride, and 

 1>\ mercuric nitrate with the gradual addition of sodium carbo- 

 nate. 



65. Sarkin (Hypoxanthine). Evaporate the alcohol 

 from the filtrate (6) upon the water-bath ; dilute it with water ; 

 render it alkaline by ammonia, and then add an ammoniacal 

 solution of silver nitrate. Sarkin will be precipitated. Let the 

 flocculcnt precipitate subside ; wash it several times by decan- 

 tation with water containing ammonia; throw it on a smooth 

 porous iiltcr, and wash it thoroughly ; push a glass rod through 

 the bottom of the filter, and wash the precipitate with nitric 

 acid of 1.100 sp. gr. into a small flask. Heat it to boiling, and 

 add more nitric acid till the whole is dissolved. The fluid 

 should be kept nearly boiling. Sometimes a few flakes of 

 silver chloride remain undissolved. Decant the liquid from 

 them into a beaker, and let it stand for six hours. A double 

 nitrate of silver and hypoxanthine will crystallize out. 



Decant the liquid (c) from the crystals and preserve it for 

 the preparation of xanthine. Wash them with an ammoniacal 

 solution of silver nitrate to remove the free acid. Suspend them 

 in water, and pass hydrogen sulphide through it. Filter from 

 the silver sulphide, and evaporate the filtrate. The hypoxan- 

 thine will crystallize out. 



In its reactions it resembles xanthine, but differs from it in 

 being precipitated by silver nitrate. 



66. Xanthine. To the mother liquor (c) of the hypoxan- 

 thine add ammonia in excess. A floccnlent precipitate of nitrate 

 of silver and xanthine w r ill fall. Wash it by decantation ; sus- 

 pend it in boiling water, and decompose it by hydrogen sul- 

 phide. Filter and evaporate. The xanthine will separate as a 

 scaly film. 



Ws/s. Put a little xanthine in ammonia. It will dissolve. 

 Add a little nitric acid to a portion of xanthine in a porcelain 

 capsule; evaporate to dryness. A yellow residue will remain. 

 Add a drop of caustic soda to it, and it will become red. Heat 

 it, and the color will change to purple red. 



