58 ANALYSIS AND ADULTERATIONS OF BUTTER. 



from the same merchant, we think we are fully justified in 

 doubting their genuineness. Several similar cases have come 

 under our notice, but in every instance the butters were im- 

 ported from abroad, and no guarantee for their purity existed. 

 On the other hand, we have frequently determined the quan- 

 tity of insoluble fatty acids in articles acknowledged to be 

 mixtures, such as "butterine," and always found the figures 

 to come to about 92 or 93 per cent., or even more, corre- 

 sponding to an addition of foreign fat amounting to two-thirds 

 to three-fourths of the whole article. 



Butter-fat, when exposed to the action of the air, is 

 considerably changed in appearance, slowly at ordinary and 

 quicker at higher temperatures. It becomes perfectly white 

 and tallowy, acquiring a very acrid, rancid smell. One might 

 be inclined to think that a change so greatly altering and 

 apparently destroying all characteristics of butter, could not 

 be without a deep influence upon its composition and upon 

 the percentage of the insoluble fat acids. Now, although 

 this change doubtless influences and alters the quantity of 

 the fatty acids, yet it takes place to so slight an extent as not 

 to interfere in the least with the accuracy of the method, as 

 will be apparent from the following determinations. 



A first-class butter, which yielded in its fresh state 8 7 '48 

 and 8 7 *5 7, or on an average 87*52 per cent, of insoluble 

 fatty acids, was exposed to the air for about four months, a 

 thin layer being spread out on a glass plate properly 

 sheltered from dust and moisture. The white, tallowy mass 

 into which the butter was found to be converted at the end 

 of that time, was again analysed, and yielded 87*90 per cent, 

 of fatty acids. Of course butter could not be sold in so 

 decomposed a condition as was presented by the sample 

 analysed. The above results, which are corroborated by 

 many similar instances, therefore show decisively that the 

 percentage of insoluble fatty acids is not altered to any great 



