190 The Analysis of Dairy Produce [316-319 



BUTTER ANALYSIS 



In the ordinary commercial analysis of butter, estimations 

 are made of water, fat, curd, and salt, though as a rule the fat 

 is estimated by difference. When the presence of foreign fat — 

 i.e., fat not derived from milk — is suspected, the fat undergoes 

 further manipulation. 



316. Water. — Five grams are weighed out in a flat 

 porcelain dish of the same shape and size as that used for the 

 determination of ' total solids ' in milk. The dish is placed 

 in a steam oven until all the globules of water which gather 

 beneath the fat on melting have disappeared. The dish is then 

 re-weighed. The loss is taken as water. 



317. A rapid method which, in skilful hands, gives good 

 results is performed by placing the dish with the weighed 

 quantity on a sand bath, and stirring constantly with a short 

 glass rod which has been weighed with the dish. By holding 

 a perfectly clean polished watch glass over the hot fat from 

 time to time, it can be seen whether steam is rising from the 

 dish, as steam will dim the surface of the glass. The operation 

 only takes a very few minutes. 



318. Curd. — Mix the dry fat from the last operation with 

 about 10 c.c. of ether. Filter the liquid so formed either 

 through a weighed filter or, better, through counterpoised 

 filters, such as are used in the determination of potassium 

 described in paragraph 34. 



Wash the filter and its contents with ether until, on evapor- 

 ating a drop of the filtrate, no residue is left. Dry the filter in 

 a water bath, and weigh. The weight gives curd plus ash. 



319. Ash. — Transfer the filter paper containing the curd 

 and ash to a weighed platinum dish and ignite over an Argand 

 at the temperature used in the determination of CaC0 3 (see 



