68 MILK PRODUCTS 



are treated with picric acid solution. A pre- 

 cipitate indicates gelatin. In this case, the re- 

 mainder of the solution is evaporated to small 

 bulk, and mixed with a io% solution of tannin 

 until no more precipitate is produced. The 

 liquid must in this treatment not have a tem- 

 perature of over 60°. To it a few c.c of white of 

 egg are added and the mixture heated to boiling 

 for thirty minutes, filtered hot, concentrated 

 to small bulk on the water and allowed to cool 

 and gelatinize. 



