HANDBOOK FOR BIO-CHEMICAL LABOBATORY, 95 



the presence of cholesterin a reddish-violet residue is first ob- 

 tained and then a bluish violet. 



SCHIFF'S Test (Urea). Place a drop of a concentrated 

 watery solution of furfurol on the crystal of urea and then a 

 drop of hydrochloric acid of sp. gr. 1.10. A change of color 

 from yellow, green, blue, to purple is obtained. Allantoin 

 gives this same reaction, but less intense and not so quickly. 



SCHROEDER'S Test ( Urea). Place a crystal on a microscope- 

 slide and add a solution of bromine in chloroform. Urea will 

 not dissolve therein, but is decomposed with the develop- 

 ment of gas. 



SCHULZE'S Reagent (Cellulose). Dissolve iodine to satura- 

 tion in a zinc chloride solution of sp. gr. 1.8 to which 6 parts 

 potassium iodide has been added. Cellulose turns blue with 

 this reagent. 



SCHULZE'S Test (Cholesterin). Evaporate the substance to 

 dryness on the water-bath in a porcelain dish with nitric acid. 

 A yellow residue is obtained with cholesterin, which turns 

 yellowish red on the addition of ammonia. 



SCHULTZE'S Test (Proteids). Add a few drops of a dilute 

 cane-sugar solution and then concentrated sulphuric acid to 

 a solution of the proteid and warm the mixture to 60 C., 

 when a beautiful bluish-red coloration is obtained. It is 

 important to keep the temperature at 60 C. 



SCHWEITZER'S Reagent (Cellulose). Sulphate of copper in 

 solution, to which some ammonium chloride has been added, is 

 precipitated with caustic soda ; the hydrated cupric oxide 

 thus obtained is washed and dissolved to saturation in 20$ 

 ammonia. It may also be prepared by pouring ammonia on 

 copper turnings, the requisite oxidation of the copper being 



