ADULTERATION OF BUTTER. 365 



molecular weight of the insoluble fatty acids in butter is 

 about 260, and varies but little from this figure, while the 

 corresponding figure for coconut oil is about 200. The iodine 

 absorption of coconut oil is also low, about 9 per cent. ; while 

 butter absorbs about 34 per cent, of iodine. Mercier's or Hink's 

 microscopic methods should be used before the presence of 

 coconut oil is certified. 



It is far more difficult to detect other adulterants, if present 

 in small quantities, unless vegetable oils are detected. Genuine 

 butters which are below the average in the Reichert figure give 

 high insoluble and low soluble fatty acids, a high iodine absorp- 

 tion, and a low percentage of potash absorbed. In the few 

 samples that the author has examined the mean combining 

 weight of the insoluble fatty acids has not been so high as would 

 be expected. Thus the mean combining weight of the insoluble 

 fatty acids is about 260, while the mean combining weight of 

 the insoluble fatty acids of most adulterants is about 277. The 

 Valenta test is also useful, and the density may be used as a 

 corroborative test. 



Margarine. It is advisable to calculate from the mean figures 

 yielded by genuine butters and margarines the apparent per- 

 centage of margarine present. If the percentage thus calculated 

 from the mean combining weight of the insoluble fatty acids, 

 the Valenta value, and the density be less than that calculated 

 from the other determinations and, at the same time, the iodine 

 absorption and refractive index are slightly high, it is probable 

 that the butter is genuine. If the contrary is the case, and the 

 apparent percentages from all the methods give approximately 

 the same value, it is probable that the butter is adulterated, 

 especially if the Ave-Lallemant method shows adulteration. 

 If, in addition, the colour tests for vegetable oils have given 

 distinct reactions, the probability of adulteration is strengthened, 

 and the presence of phytosterol may be considered conclusive. 



Though in the present state of science it is not possible 

 definitely to certify many cases of small amounts of adulteration, 

 for dairy control work the task is much simplified. The samples 

 which must be regarded as suspicious can be reported as such, 

 or even as adulterated, with a high degree of probability, and it 

 will be possible frequently to trace such samples to their origin, 

 by examining the fat of the milk of the cows which yielded the 

 butter. 



Influence of Keeping on the Analytical Properties of 

 Butter. When butter is kept and becomes rancid very pro- 

 nounced changes take place in the composition of the fat. These 

 may be classed under two heads hydrolysis and oxidation. If 

 butter fat be kept in the dark and out of contact with the air, 



