640 MILK 



1 to 2 c.c. at a time, mixing contents after each addition, until 

 the color of the mixture becomes dark chocolate brown. 



"Whirl in a Babcock machine for five minutes, fill with boiling 

 water to bottom of neck, and whirl one minute. 



"Read the fat column and multiply the reading by 2." 



Notes on Above Method. — "A uniform mixture before weigh- 

 ing out samples is, of course, essential to accurate and uniform 

 results. 



"Too long heating or overheating of the mixture of acetic acid 

 and ice-cream has practically no effect on the results. Heating 

 for five to ten minutes in water slightly below boiling temperature 

 is usually sufficient. The hotter the mixture is, the less sulphuric 

 acid will be required to produce the proper color. 



"The fat column should be perfectly clear and free from any 

 curd or char. In case the fat column contains curd or char, 

 duplicate the test, adding sulphuric acid to a darker color in the 

 case of interfering curd, or to a lighter color in the case of inter- 

 fering char. 



"With very little practice in judging this color, perfect fat col- 

 umns may be obtained in every test." 



Good results are also obtained by using 20 c.c. of a mixture of 

 equal parts of hydrochloric and glacial acetic acids in place of 

 sulphuric acid, called for in the original Babcock method. This 

 mixture of acids does not produce heat as sulphuric acid does, 

 and, therefore, the bottles containing the ice-cream acid mix- 

 tures should be warmed to the proper temperature by immersion 

 in a water-bath. Otherwise the test is carried out as the Bab- 

 cock test is executed. 



Instead of the mixture of acetic acid and hydrochloric acid, 

 the following mixture may be used: 25 c.c. each of hydrochloric 

 acid and fusel oil are mixed and shaken occasionally for three 

 hours. To this are added 450 c.c. of glacial acetic acid and the 

 mixture allowed to stand for twenty-four hours. For a 9-gram 

 sample of ice-cream 5 c.c. of the mixture are used. 



Another method, according to Benkendorf, is the following: 

 88 parts of commercial sulphuric acid are poured into 12 parts of 

 concentrated nitric acid. Weigh 18 grams of ice-cream into a 

 dry beaker, add 4 to 5 c.c. of the acid mixture, and mix by a 

 rotary motion. If the contents do not assume a dark brown color, 

 add 2 to 3 c.c. more of the acid. Then transfer to a 30 per cent, 

 cream bottle, rinse the beaker with hot water, and add this to the 

 contents of the bottle. Then proceed in the usual manner. 



The Illinois State Food Commission gives the following method 

 for calculating the percentage of milk-fat in ice-cream, according 

 to the contents of a gallon can : 



