156 MILK 



the assembling of the fat in the graduated neck of a specially 

 constructed bottle so that the percentage can be read off. 



The sulphuric acid dissolves the casein and removes thereby 

 the substance that holds the fat globules in suspension. The 

 heat which is generated by mixing the acid and milk causes the 

 released fat globules to coalesce and form a layer of melted fat on 

 the surface. The sulphuric acid, furthermore, increases the 

 specific gravity of the mixture, thus facilitating the complete 

 separation of fat. 



The apparatus required for the test are as follows : 



A pipet measuring 17.6 c.c. 



Specially constructed testing bottles. 





Fig. 43. To mix the acid and milk shake the bottle until the contents 

 are of a uniform brown color. (Circular of Information No. 27, July, 1916, 

 Univ. of Wis. Agri. Exp. Sta.) 



A glass cylinder to measure 17.5 c.c. sulphuric acid. 



A pan for heating water. 



A pipet or other instrument for adding the hot water. 



A centrifuge. 



An acidometer. 



The following chemicals are needed: 



Sulphuric acid of specific gravity of 1.82 to 1.83. 



A solution of glycerin consisting of 80 per cent, glycerin and 

 20 per cent, water. 



Fat-saturated alcohol. 



Fat-saturated alcohol is prepared by dissolving a teaspoonful 

 of melted butter in warm alcohol. The fat from cream testing 

 can be used to advantage. The bottle containing the alcohol and 



