36 MICRO-CHEMICAL REAGENTS. 



which contain grape sugar (glucose) become clouded 

 by the deposition of a finely granular or fiocculent 

 orange precipitate of reduced oxide of copper. 



By this test we are thus able to determine which 

 kind of sugar was present in the tissue. If the 

 blue solution of cane sugar is boiled with dilute 

 sulphuric or nitric acid it is changed into grape 

 sugar, which then gives the red reaction. 



Trommer's test also serves for the detection of 

 dextrine. The contents of cells containing this 

 sugar assume a vermilion color, while small gran- 

 ules in the precipitate exhibit the Brownian 

 movement. If the dextrine is mixed with pro- 

 tein compounds, however, the precipitate is yel- 

 lowish. 



If in manipulation too much of the cupric sul- 

 phate has penetrated the cells the reaction is often 

 masked by a precipitate of cupric hydrate. To 

 avoid this difficulty Fehling's fluid, which gives the 

 same reaction, may be used. It is prepared in the 

 following manner. Dissolve 4 gm. of cupric sul- 

 phate in 16 gm. distilled water; and 16 gm. of 

 potassium tartrate in the minimum of water. The 

 two solutions are to be mixed. The reagent 

 should be kept in the dark and needs frequent 

 renewal. 



[Prof. W. S. Haines has found in glycerine a 

 very desirable substitute for the tartrate in Feh- 

 ling's test. The proportions employed by him for 

 qualitative examinations are : Cupric sulphate, 2 



