BY DR. LAUDER BRUNTON. 539 



with zinc chloride. It should be collected on a filter and 

 washed with pure spirit; the substance left on the filter con- 

 sists of chemically pure chloride of zinc-creatinine (C 4 H 7 N 3 0) 2 , 

 ZnCl 2 . This most characteristic compound is very slightly 

 soluble in cold water and insoluble in cold alcohol ; it crystal- 

 lizes from urine in the form of bundles of needles. 



From chloride of zinc-creatinine, the pure substance is 

 obtained by boiling with freshly prepared and thoroughly 

 washed hydrate oxide of lead for half an hour or longer. On 

 filtering the fluid, and evaporating to dryness, creatinine is 

 obtained, which ma3 r be dissolved in alcohol and crystallized. 



Creatinine is very soluble in cold alcohol. The following 

 experiments may be performed with it : 



1. When a few drops of a solution are allowed to evaporate 

 spontaneously, colorless prisms are obtained (fig. 302). 



2. The taste of the solution is strongly alkaline. 



3. The reaction to test-paper is intensely alkaline. 



4. A concentrated solution of chloride of zinc added to 

 creatinine, causes the immediate precipitation of the zinc com- 

 pound, which is always crystalline. 



** 189. Separation of the Coloring matters of 

 Urine. Under various names, among others that of Urohae- 

 matine, different writers have described the substance, or 

 mixture of substances, which i\\ey considered to be the cause 

 of the color of healthy urine (Scherer, Harley, Heller). We 

 are now perfectly convinced that no one coloring matter, capa 

 hie of accounting for the normal, golden, or amber color of 

 human urine, has been separated. 



The following experiments may be performed, as they throw 

 some light on the reactions of the normal urinary coloring 

 matter : 



1. Take 200 cubic centimetres of urine and precipitate with 

 neutral acetate of lead ; an abundant precipitate falls, which 

 consists of lead salts of acids "present in the urine, and which 

 contains a portion of the urinary coloring matter. Filter, and 

 observe that the filtrate from this precipitate is not altogether 

 colorless. Add to the filtrate basic acetate of lead, when a 

 further precipitate will fovm, which, when separated, leaves a 

 colorless filtrate. 



Now unite the precipitates caused by neutral and basic 

 acetates of lead, and treat the mixture with alcohol acidulated 

 with hydrochloric acid. A red fluid will be obtained, which, 

 on filtration and evaporation, yields a reddish-black residue, 

 insoluble in water. 



That this [a not, as was supposed, the coloring matter of 

 urine, is now admitted. The researches of Dr. Harley, although 

 failing to discover any one normal urinary coloring matter, show 



