1847.] Butter Churning. 165 



per rent 



Curd and envelopes, - - - - ^^ lo 1 



Water, 10 to 14 



Fat, 89^ to 85 



JOO 100 



When butter is salted, a portion of the water separates, and the 

 butter becomes harder, closer, and more rich in fat. 



The fat of butter consists of a solid and a liquid portion. The 

 former is called margai iiie, and the latter elaine. When butter is 

 put into a linen bag, and submitted to the action ot a press, the 

 elaine flows out. 'J'he larger the propoition of margarine, the 

 more solid is the butter; the laiger the quantity of elaine, the 

 softer it is. 



At this latter fact the chemical interest of our practical ques- 

 tion begins: If the haidness of butter depends upon the propor- 

 tion of margarine, and if the hardness is found to vary, the pro- 

 portion of margarine must vary also. And this, upon careful 

 chemical investigation, is really found to be the case.* 



What, then, is the chemical relation between the solid and 

 liquid tats of butter? Are they capable of being changed, the 

 one into the other? Are the circumstances under which butter is 

 churned such as naturally to give rise to such a change? Are 

 they such as to cause this change to take place to a greater ex- 

 tent at one time, or at one season than at another? 



1. 7'Ae Chemical Relation of the two Fats. — For the sake of 

 clearness it may be proper first to state, that both margai ine and 

 elaine, when treated in a particular way, yield a sweet sugary 

 substance, to which the name of oil sugar, or glycerine, has been 

 given. When this sweet substance is separated, the former hiS 

 become changed into margaric acid, and the latter into elaicacid. 

 It is the composition of these two acids, therefore, that we have to 

 compare with each other. When combined with the same sub- 

 stance, glycerine, they form respectively the natural fats, marga- 

 rine and elaine. 



IS'ow, margaric and elaic acids are represented respectively! — 



These numbers show that elaic differs from margaric acid only 

 in containing two equivalents more of carbon. By the action of 



• See my Lectures on Aijriculluial Chemistry and Geolosy, 2J ed., p. 964. 



t The pure chemist will observe that I have, for i\v sake of simplicity, 

 omilte I an equivalent of water, in respect of which the iwo acids also differ 

 from eatjh other. 



