EXPERIMENT 73. TO DETECT ALUM IN BAKING POWDER 



To about 2 gm. of flour add gm. of baking powder. 

 Pour on this enough water to make a thin dough, and then 

 add several drops of tincture of logwood and ammonium 

 carbonate solution. Mix the mass thoroughly and note the 

 color. A blue hue indicates the presence of alum. 



Try this test on flour to which no baking powder has 

 been added, and note the color. 



EXPERIMENT 74. TO DETECT FORMALDEHYDE IN MILK 



Put a small amount of milk in a casserole and add an 

 equal quantity of acid reagent.* Heat slowly over a slow 

 flame, shaking the casserole from time to time in order to 

 prevent the curd from collecting in a lump. 



Just before the boiling point is reached, remove the ves- 

 sel from the fire, and note the color of the cooling liquid. 

 If the solution turns brown, no formaldehyde is present in 

 the milk; if, however, the solution shows a violet color, for- 

 maldehyde is present as a preservative. A faint violet 

 coloration indicates the presence of a small quantity of this 

 preservative ; a deep coloration indicates the presence of 

 a large amount. 



EXPERIMENT 75. TO DETECT GELATIN IN MILK AND ICE 



CREAM 



Put 30 c.c. of acid mercuric nitrate and 60 c.c. of pure 

 water into 30 c.c. of milk or ice cream. Allow this mixture 



* The acid reagent for this experiment is made by adding to I liter bi 

 hydrochloric acid, 2 c.c. of a 10 per cent solution of ferric chloride. 



