DETECTION OF ADULTERANTS AND PRESERVATIVES 303 



and placed in a water bath at 80 degrees C. for five minutes. In the 

 case of the presence of sucrose the solution becomes more or less 

 blue according to amount of sucrose present. Upon standing in the 

 water bath for a longer time the blue color becomes deeper. At the 

 end of ten minutes it is deep blue, while in the absence of sucrose at 

 the end of five minutes the color is faintly green, which deepens, 

 but never acquires a blue shade. By means of this method as little 

 as .05 per cent sucrose can be detected. 



Detection of Lime in Milk 1 



Shake 250 c.c. of milk at 15 degrees C. with 10 c.c. of a 10 per 

 cent solution of hydrochloric acid. Let stand at room temperature 

 for half an hour- Filter, returning the first portion of filtrate to 

 the filter. Cover filter to prevent evaporation. 



Pour 104 c.c. of the filtrate (equal to 100 c.c. of milk) into a 

 200 c.c. flask, add 10 c.c. of a 10 per cent solution of ammonia and 

 fill the flask to the mark with water at 15 degrees C. Let stand for 

 thirty minutes. Filter through folded filter, pouring back on the 

 filter the first portion of the filtrate. Test 100 c.c. of filtrate (equiv- 

 alent to 50 c.c. of milk) with 10 c-c. of 5 per cent ammonium 

 oxalate solution and proceed with the determination of the lime in 

 the usual way, but without warming the liquid. 



According to Baier and Neumann and corroborated by Luhrig, 

 in normal milk the lime in the serum is present to the extent of 

 thirteen to eighteen milligrams per 100 c.c. In milk to which 

 sucrate of lime has been added the results are correspondingly 

 higher. 



Detection of Gelatin 2 



"Prepare an acid solution of mercuric nitrate by dissolving mer- 

 cury in twice its weight of nitric acid of 1.42 specific gravity, and 

 diluting this solution to twenty-five times its bulk with water. To 

 10 c.c. of the milk or cream to be examined, add an equal volume 

 of the acid mercuric nitrate solution, shake the mixture, add 20 c.c. 

 of water, shake again, allow to stand five minutes, and filter. If 

 much gelatin is present the filtrate will be opalescent and cannot be 

 obtained quite clear. To a portion of the filtrate contained in a test 



1 Barthel, Milk and Dairy Products. 



2 United States Department of Agriculture, Bureau of Chemistry, Bulletin 



107, 1912, 



