LIQUID PARTS OF ANIMALS. 



66. The alcohol being decanted off and distilled over the wa- 

 ter-bath, left an oil which had an acid reaction, and the smell of 

 butter. This oil was butyrin, mixed with a little elain. The 

 acid reaction was owing to the property which alcohol has of par- 

 tially decomposing the butyrin and developing a portion of the 

 volatile acids which it furnishes, They may be removed by di- 

 gesting the butyrin with a mixture of water and magnesia. A 

 salt of magnesia soluble in water is formed, and the butyrin be- 

 comes neutral. 



Butyrin in this state is an oil, sometimes yellow, sometimes 

 colourless. It has the taste and smell of butter, and becomes 

 solid when cooled down to 32. It is miscible in all proportions 

 with boiling alcohol of 0-822. According to Chevreul, a mix- 

 ture of 2 parts butyrin and 10 parts alcohol becomes muddy on 

 cooling, while a mixture of 12 parts butyrin and 10 parts alco- 

 hol retains its transparency. The alcoholic solution becomes 

 always acid, and the more so the longer the digestion continues. 

 Butyrin is easily saponified. The fatty acids evolved by this pro- 

 cess begin to solidify at 90, but do not become quite solid till 

 cooled down to 63. 



When the elain from butter is digested for a long time in ab- 

 solute alcohol, the butyrin dissolved becomes more and more 

 charged with elain as the process advances. If we digest it three 

 times successively with twice its weight of absolute alcohol, the 

 remaining elain which separates from the last portion of alcohol 

 as it cools is as free from butyrin as it can be made by this pro- 

 cess. It is not the least acid while the alcoholic solution red- 

 dens litmus. The specific gravity of this elain is 0-92 at 66. 

 Alcohol of 0-822 dissolves only four-fifths of a per cent, of it 



These three constituents of butter, namely, stearin, elain, and 

 butyrin, are all analogous to salts, being combinations of certain 

 oily acids and glycerin. 



When butter is saponified by means of potash, or rather when 

 the liquid portion of butter is treated in this way, and the soap is 

 afterwards decomposed by adding a quantity of tartar ic acid suf- 

 ficient to convert the potash into bitartrate, the oily acids are 

 disengaged. The fatty acids are now washed with water, and 

 the water is distilled. The three peculiar acids of butter pass 

 over with the water into the receiver. These acids are the bu- 

 tyric, the caproic, and the capric. An account of these acids 



