46 ANALYSIS AND ADULTERATIONS OF BUTTBE. 



used as adulterants witli, or substitutes of butter, if we except 

 tbe small quantity of palm oil, used to impart a yellow colour 

 to such mixtures. 



The equivalents of these glycerides, and of the acids they 

 furnish on decomposition, being very high and but little 

 differing from each other, theory predicted that they would 

 yield, on saponification and decomposition of the soap with 

 dilute mineral acid, nearly equal amounts of fatty acid. 

 Thus pure palmitin would yield 95 '28 per cent, of palmitic 

 acid ; pure stearin, 95"73 per cent, of stearic acid, and lastly, 

 olein 95 '70 per cent, of oleic acid. 



All fats therefore, being mixtures of these three glycerides, 

 should yield percentages of fatty acids ranging between 

 95'28 per cent, and 95-73 per cent., or as stearic and oleic 

 acids for the most part predominate, on an average about 95 '5 

 per cent. As the three acids named are insoluble in water, 

 we may therefore assert that all animal fats except butter-fat 

 furnish 95-5 per cent, of insoluble fatty acids. 



Butter, containing as we have shown, a considerable pro- 

 portion of volatile acids, which at the same time are more or 

 less soluble in water, should therefore furnish a lower amount 

 of insoluble acids, these being diminished in ratio to the 

 quantity of the insoluhle acids. 



This reasoning proved to be strictly in accordance with the 

 facts. Numerous determinations of the amount of insoluble 

 fatty acids in animal fats, such as taUow, lard, and dripping, 

 proved the correctness of the theory, results Ijeing obtained 

 closely approaching 95 '5 per cent., whilst butter yielded on 

 an average of twelve experiments made on different samples 

 but 85 '85 per cent., the results ranging from 85*4: to 86*2 per 

 cent. The plan followed was shortly this. A weighed quan- 

 tity of the fat, conveniently about three grammes, was saponi- 

 fied in a small porcelain hasin, by means of a concentrated 

 aqueous solution of potash, the liquid being kept boiling, or 



