320, 321] 



Butter Analysis 



191 



paragraph 45). When the ash is quite white, weigh the dish 

 again. By subtracting the weight of ash from the weight of curd 

 plus ash obtained in the last experiment, the weight of curd 

 is found. Of course it must be remembered that the weight 

 of the ash from the filter has to be subtracted from the total 

 ash. 



Generally speaking, almost the whole of the ash is salt. 

 This may, however, be determined by dissolving in water and 

 estimating the chlorine with standard AgN0 3 solution, as 

 described in paragraph 69. 



320. Enter the results as follows : 



Estimation of Foreign Fats in Butter 



321. Butter Fat. — All pure fats are compounds of the 

 trihydric alcohol glycerin with monobasic organic acids. As 

 glycerin is always present, the identification of any fat depends 

 on the identification of the acid which it contains. Unfortu- 

 nately for the analyst, there are very many of these so-called 

 1 fatty ' acids which resemble one another so closely as to make 

 their separation a matter of great difficulty. Another difficulty 

 arises from the fact that pure fats are seldom or never found 

 in nature. In the investigation, therefore, of such natural fats 

 as ' butter fat ' or ' margarine,' experiments must be made on 

 the mixed compounds of glycerin and a number of fatty acids. 



