68 Testing Milk and Its Products. 



or in the temperature of the milk influences the in- 

 tensity of the action of the acid on the fat, as shown in 

 the color of the fat obtained. 



The following experiment shows the relation between 

 the strength of the acid, the temperature of the milk, 

 and the color of the fat: 



First: From a sample of milk measure the usual quantity 

 for testing into each of three bottles, A, B and C. Place A in 

 iced water, and C in warm water, leaving bottle B at ordi- 

 nary temperature. After the bottles have been left for ten min- 

 utes under these conditions, add the normal quantity of acid 

 to each and proceed with the test in the ordinary manner. 



Second: Measure some of the same milk into three other 

 bottles, D, E and F. Into test bottle D pour the usual amount 

 of rather weak acid; add the same amount of acid of normal 

 strength (1.82-1.83) to bottle E, and add 17.5 cc. of a still 

 stronger acid (concentrated sulfuric acid, sp. gr. 1.84), in test 

 bottle F; complete the tests in the usual way. 



On the completion of the preceding six tests the operator will 

 notice that the fat in the necks of test bottles A (cold millc) 

 and D (weak add) is much lighter colored than that in C (warm 

 milk) and F (strong acid), and that the color of the fat in B 

 (normal temperature) and E (normal acid) is somewhere be- 

 tween that of these two series. 



79. Influence of temperature on the separation of 

 fat. The intensity of the action of the sulfuric acid 

 on the milk is influenced by the temperature of either 

 liquid; the higher the temperature, the more intense 

 will be the action of the acid on the solids of the milk. 

 It may be noticed that acid from the same carboy will 

 act differently on milk in summer than in winter time, 

 if the acid and the milk are not brought to a tempera- 

 ture of about 70 before testing during both seasons. 

 The temperature of the liquids may be as low as 40 F. 

 in winter and as high as 80 F, in summer. This dif- 



