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a linen wrapj^er and pressing it forcibly at a temperature 

 of sixty degrees, a slightly yellow fluid oil is procured 

 from it, while a solid, pure white fat remains in the 

 cloth. This solid white fat is called margarine from its 

 pearly appearance ; the fluid oil is called oleine, butter- 

 oil, or oil of butter, and sometimes butyrine. 



These two fatty substances are themselves compound 

 in character, for if treated with a hot solution of caustic 

 potash they readily dissolve and form soap. When one 

 of these soaps made from the margarine is dissolved in 

 water and decomposed by the addition of diluted sul- 

 phuric acid, a white waxy substance separates, and after 

 having been dried and dissolved in hot alcohol, crystal- 

 lizes on cooling into pearly scales. This substance has all 

 the properties of an acid and is known as margaric acid. 



When the other (the oleine) soap is treated in a similar 

 way an oily substance is separated, differing from the 

 butter oil and having all the properties of an acid. This 

 substance is known as oleic acid of butter, because it has 

 never been obtained from any other substance than the 

 oil of butter. The liquid remaining after the separation 

 of these acids contains a sweet, syrupy, oily substance 

 which,, when separated, is the glycerine so well known as 

 the base of neutral oils and fats. 



The composition of butter varies considerably in regard 

 to the proportion of these fatty bodies, margarine and 

 oleine. In summer the proportions of these fats are 

 about as follows: 



COMPOSITION OF SUMMER BUTTER. 



Marsrarine 40 percent 



Oleine - -^ " 



100 



In winter this proportion is nearly reversed, as follows: 



COMPOSITION OF WINTER BUTTER. 



Margarine - 65 per cent 



Oleine - 35 " 



lOQ 



