DETECTION OF ADULTERATIOX. 353 



Detection of Adulteration of Butter. — The most useful and 



rapid preliminary test is examination with the butyro-refracto- 



meter. Any sample showing a refractive index of less than 



46° at 35° C. is most probably genuine, but may, however, contain 



coco-nut oil. The Reichert-Wollny process should next be 



applied. Any sample requiring less than 20 c.c. for 5 grammes 



may be taken as adulterated ; samples requiring more than 



28 c.c. may be passed as genuine, though they cannot absolutely 



be certified as free from adulteration. Any sample taking a 



N . 



volume of ^ alkali between the limits given above must be 



further examined. The Polenske and A\'c-Lallemant methods 

 should be employed, and if the results are suspicious the phyto- 

 steryl acetate test should be used. Baudouin's, Becchi's, Hal- 

 phen's, and Wellmann's tests should be applied. A well-marked 

 reaction with any or all of them will furnish strong presumptive 

 evidence of the presence of margarine containing vegetable oils. 

 The soluble and insoluble fatty acids, saponification equivalent, 

 and especially the mean molecular weight of the insoluble fatty 

 acids should be determined. 



Coco-nut oil can be readily detected by tlic figures thus 

 obtained. A high Polenske figure indicates this adulterant. 

 The ratio between the Reichert-Wollny figure and the differ- 

 ence between the insoluble fatty acids and 9.5 '5 is much 



R -W 

 depressed ; in butter the ratio is about - ,. ,- = 35 (R-\V = 



Reichert-Wollny figure, and I = Insoluble fatty acids) ; while 

 coco-nut oil gives a value of approximately 075. The mean 

 molecular weight of the insoluble fatty acids in butter is 

 about 259, and varies but little from this figure, while the 

 corresponding figure for coco-nut oil is about 200. The iodine 

 absorption of coco-nut 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 

 coco-nut 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 259, while the mean combining weight of 

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



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