LARD AND LARD ADULTERATIONS. 425 



lard when treated with sulphuric or nitric iicid, depends chiefly upon 

 the percentage of cotton oil which it contains. Since from a commercial 

 point of view the introduction of a small amount of cotton oil would not 

 prove profitable, we find in the adulterated lards of commerce, as a gen- 

 eral rule, strong color reactions. It might be possible, however, to mix 

 with a pure lard so small a quantity of cotton oil as to render doubtful 

 to the analyst the character of the color reaction produced. Some of 

 the colors produced in the adulterated lards examined, as copied from 

 the note-books, are as follows : "light brown," "pink red brown," "light 

 yellow red," " light pink," " deep brown," " red," " deep red brown," etc. 

 The appearance of a pinkish tint is often found in adulterated lards 

 containing a notable portion of beef-fat steariue, although this colora- 

 tion is not considered a certain indication of the presence of this sub- 

 stance. 



(d) Refractive index. The refractive index of the mixed lards naturally 

 varies with the proportion of cotton oil which may be present. The 

 greater the quantity of cotton oil the higher the refractive index. The 

 refractive index of the Armour mixed lards is decidedly lower than that 

 of the Fairbank samples. The following is the number representing 

 the mean refractive index of the Armour samples at 25, viz, 1.4634. 

 The number representing the mean refractive index of the Fairbank 

 samples is 1.4651. The refractive index is a much more important prop- 

 erty in the sorting of lards than the melting point. 



(e] Rise of temperature icith sulphuric acid. As is to be expected, we 

 find here also great variation, depending on the nature and the quan- 

 tity of the adulterants present. The presence of tallow steariue tends 

 to diminish the rise of temperature with sulphuric acid, while cotton- 

 oil has the opposite eifect. As the relative proportion of these two 

 ingredients and also the amount of pure lard varies, we may expect 

 corresponding variation in the temperature shown on mixing the lard 

 with sulphuric acid. In the samples of Armour's lards examined, the 

 highest rise of temperature noticed was 58.9 and the lowest 42.1. 

 This latter number is almost identical with that furnished with pure 

 lards. In Fairbanks lards the least rise of temperature noticed was 

 51.3 and the greatest 68.8. These numbers show a larger proportion 

 of cotton oil in the Fairbank than in the Armour samples. This rise 

 of temperature as a diagnostic sign is valuable, and its determination 

 should never be omitted. 



(/) Crystallization point of fatty acids. In Armour's lards the mean 

 temperature of crystallization for the fat acids was found to be 39.8. 

 In the Fairbank Lords it was 37.4. 



({/) Melting point of fat acids. The mean melting point of the fat acids 

 in the Armour samples was 42.8. In the Fairbank samples it was 

 40.0. 



