Chemical Analysis of Milk and its Products. 217 



filtered off, and the residue transferred to a filter and 

 dried; its nitrogen content is then determined by the 

 Kjeldahl method (253). The nitrogen in the filter and 

 the chemicals used is determined by blank trials and de- 

 ducted. The nitrogen multiplied by 6.25 gives the 

 casein in the butter. 



266. d. Ash. 1. 10 grams of butter are weighed into 

 a porcelain dish and treated twice with gasoline, as in the 

 preceding determination; the solution is filtered through 

 an ash-free (quantitative) filter, and the filter when dry 

 is transferred to the dish. The dish is heated in an air- 

 bath for half an hour and then placed in a muffle oven, 

 where the contents are burnt to a light greyish ash; the 

 dish is now cooled in a desiccator and weighed. The 

 difference between this weight and that of the empty dish 

 gives the amount of ash in the butter weighed out. 



267. 2. About two grams of butter are weighed into a 

 small porcelain dish, half filled with stringy asbestos; the 

 dish is dried for an hour in the water oven, and the fat 

 then set fire to with a match, the asbestos fiber serving 

 as a wick. When the flame has gone out, the dish is 

 placed in a muffle oven, and the residue burnt to a grey- 

 ish ash. After cooling, the dish is weighed, and the per 

 cent, of ash in the butter calculated as under method 1. 



268. Complete analysis of butter in the same sample. 

 About 2 grams of the butter are weighed into a platinum 

 gooch half filled with stringy asbestos, and dried in a water 

 oven at 100 C. to constant weight, cooled and weighed. 

 The difference gives water in the sample. The gooch is 

 then treated repeatedly with small portions of gasoline, 

 suction being applied, and again dried in the water oven, 



