22 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



on a crucible cover or a piece of platinum foil over a very 

 small flame. It first loses its water of crystallization and 

 becomes white like porcelain, then it turns brown, giving off 

 a characteristic odor, carbonizes, and finally burns without 

 leaving any residue if pure. 



2. Conversion into Creatinine. Heat the remainder of 

 the creatine for half an hour with 10 cc. of dilute sulphuric 

 acid (20 per cent.) on the water-bath, adding water to re- 

 place that lost by evaporation. To get rid of the sulphuric 

 acid grind the solution, after the addition of water, in a mor- 

 tar with barium carbonate until the mixture no longer reacts 

 acid, filter, and evaporate the filtrate on the water-bath to a 

 few cubic centimeters. 



(a) Creatinine Zinc Chloride, (C 4 H 7 N 3 0) 2 ZnCl 2 . In a 

 watch-glass add to a few drops of the solution thus obtained a 

 drop of an alcoholic solution of zinc chloride. A pulverulent 

 or microcrystalline precipitate of creatinine zinc chloride 

 soon separates. Examine under the microscope. 



(6) WeyPs Reaction. Mix the greater part of the solu- 

 tion with sodium nitroprusside solution (freshly prepared by 

 dissolving a few crystals in a little water) until the solution 

 has a yellow color, then add a few drops of caustic soda solu- 

 tion. The fluid turns deep red to ruby-red, the color soon 

 fades and becomes straw-yellow. If the solution is now 

 acidified with glacial acetic acid (about one-fourth the vol- 

 ume) and heated to boiling or allowed to stand for some time 

 it turns green, and deposits on longer standing a precipitate 

 of Prussian blue. 



The mother-liquor from the creatine contains the xan- 

 thine bases or alloxuric bases (earlier also called xanthine 

 bodies), which may be obtained in the form of the silver 

 compounds by adding ammonia to alkaline reaction, then 

 filtering and adding an ammoniacal silver nitrate solution 

 (see below). 



