470 FOODS AND FOOD ADULTERANTS. 



(10) By the coloration produced by boating with nitric acid and al- 

 buinen (Brall^'s inetbod). 



In the peculiar conditions attending tbe analyses of mixed lards it is 

 unnecessary to say that the most misleading results may be obtained by 

 relying on any one of the above methods, and even when all are ap- 

 plied the real quantity of added adulterants may not be determined. 



The processes indicated in Nos. 1, 2, and 3 of the foregoing classifica- 

 tion may be dismissed without further discussion. They are entirely 

 unreliable for any quantitative purpose. 



(4) BY CALCULATION' FROM SPKCIFIC GRAVITY. 



Iii the case of No. 4, approximate results could be reached were only 

 one kind of adulterant used, the specific gravity of which, as in the 

 case of cotton oil, is distinctly different from that of lard. 



But if one adulterant be used like an oleo or lard steariue having 

 a lower specific gravity, and another like cotton oil with a high one, the 

 neutralizing effect of the two will render the results of the analysis unre- 

 liable. 



Cotton oil, however, has a specific gravity considerably higher than 

 that of a stearine is below the number for pure lard ; hence a mixed lard 

 containing equal portions of cotton oil and a stearine will have a higher 

 specific gravity than pure lard. In point of fact, it may be said that 

 where one of these adulterants is present in any notable quantity, say 

 15 to 30 per cent., the other is also present in proportions approximately 

 known. It might bo possible, therefore, to construct an arbitrary for- 

 mula by which the disturbing efl'ect of the second element could be al- 

 lowed for. In this way some approximate number might be reached 

 of the respective amounts of adulterants present. 



Example : 



Let specific gravity of pure lard at 35 = . IHT> 



Let specific gravity of pure steariue at 35 = . l)i>:> 

 Let specific gravity of pure cottou oil at 35 = . 913 



The theoretical specific gravity of a mixed lard composed of tliose 

 bodies in the proportions stated would be as follows : 



20 per cent. stearine = . 903x20 = 18. 060 

 30 per cent, cotton oil = , 913x30 = 27. 390 

 50 per cent, lard = . W>x">0 = 45. i>:>u 



100 per cent. =90.700 



Then theoretical specific gravity = .907. 



It is usual to mix cotton oil and stearine in compound lards in 1 1m 

 respective proportions mentioned above, vi/, 1.5 parts to 1.* 



"Testimony of George H. Webster, Report of Hearings l>H<>-c- H..MM- ( 'nimnittea 

 on Agriculture, p. 20. 



