16 QUALITATIVE EXAMINATION OF MIEK. 



condition, in a flask holding about 150 c. c. (An Erlen- 

 meyer flask is the best form.) To this add one gram of 

 soHd potassium hydrate and 20 c. c. of 80 per cent alcohol. 

 This mixture is put on the water bath and agitated fre- 

 quently, until complete saponification is effected, the 

 mixture becoming perfectly clear and soapy in appear- 

 ance. Then, taking the flask from the bath, the soap is 

 dissolved in 50 c. c. of water and decomposed by adding 

 20 c. c. of dilute sulphuric acid (one c. c. of pure sulphuric 

 acid to 10 c. c. of water). The contents of the flask are 

 now subjected to distillation. Care must be taken to 

 prevent the bumping of the fluid, by allowing a light cur- 

 rent of air to pass through it. It is also recommended to 

 connect the distilling flask with a large bulbed tube, to 

 prevent the splashing out of the sulphuric acid. Since the 

 distillate, especially from poor butter-fats, or by rapid 

 distillation, always carries with it some solid fatty-acids, it 

 should be immediately filtered through a moist filter and 

 collected in a 50 c. c. flask. After 10 to 2p c. c. has dis- 

 tilled off, pour it back into the flask and again distill, 

 until the flask contains exactly 50 c. c. of distillate. If the 

 distillation has been carried on cautiously, the distillate 

 will be perfectly clear. This distillate is finally trans- 

 ferred to a larger flask and titrated with tenth-normal 

 sodium hydrate, using litmus tincture as an indicator. 

 The titration is considered complete when the blue color 

 of the litmus remains permanent for some time. Ac- 

 cording to Reichart, 214 grams of butter-fat require 12.15 

 c. c. to 14 c. c. of tenth-normal sodium hydrate solution. 

 Figures outside of these limits indicate impure butter-fat. 

 According to investigations of Pizzi, the milk fat of 

 different mammals shows a slight difference with refer- 

 ence to the amount of volatile fatty-acid contained, which 

 gives a means of determining the source of the milk. 



