BUTTER 55 



Fat. The dry butter from the water determination is dis- 

 solved in the dish with absolute ether or with petroleum spirit 

 (sp. gr. 0.680). The contents of the dish are then transferred 

 to a weighed Gooch crucible with the aid of a wash-bottle filled 

 with the solvent, and are washed until free from fat. The cruci- 

 ble and contents are heated at the temperature of boiling water 

 till the weight is constant. 



The fat may also be determined by drying the butter on 

 asbestos or sand 1 , and extracting by anhydrous alcohol-free 

 ether. After evaporation of the ether the extract is heated 

 to constant weight at the temperature of boiling water and 

 weighed. 



Casein, Ash, and Chlorin. The crucible containing the 

 residue from the fat determination is covered and heated, 

 gently at first, gradually raising the temperature to just below 

 redness. The cover is removed and the heat continued until 

 the material is white. The loss in weight represents casein, 

 and the residue mineral matter. In this mineral matter dis- 

 solved in water slightly acidulated with nitric acid, chlorin 

 may be determined gravimetrically with silver nitrate, or, after 

 neutralization with calcium carbonate, volumetrically, using 

 potassium chromate as indicator. 



Salt. About 10 grams are weighed in a beaker in por- 

 tions of about i gram at a time taken from different parts of 

 the sample. Hot water (about 20 c.c.) is now added to the 

 beaker, and after the butter has melted, the mass is poured 

 into the bulb of a separating funnel, which is then closed and 

 shaken for a few moments. After standing until the fat has 

 all collected, the water is allowed to run into an Erlenmeyer 

 flask, with care not to let fat globules pass. Hot water is again 

 added to the beaker, and the extraction is repeated from ten 

 to fifteen times, using each time from 10 to 20 c.c. of water. 

 The resulting washings contain all but a mere trace of the salt 

 originally present in the butter. The chlorin is determined 



