476 



FOOES AND FOOD ADULTERANTS. 



The different glycerides when mix< d do uot have a melting point which 

 corresponds to the one theoretically calculated. For this reason equal 

 mixtures of cotton seed oil and lard, instead of having a melting point of 

 about 20, really melt only at a much higher temperature. While, 

 therefore, the determination of the melting point of a compound lard 

 should not be omitted, it does not afford a basis for any reliable estima- 

 tion of a quantitative nature. 



10. Heating with nitric acid and albumen. The coloration produced 

 by heating the fat or oil under examination with nitric acid and albu- 

 men has also been proposed as a quantitative test. Although I have 

 not tried this method quantitatively, I am of the opinion that it will be 

 found of no greater value than the other color reactions already noted. 



The Brull6 test appears to be unaffected by free acid or rancidity, in 

 which point it possesses an advantage over chloride of gold and in some 

 cases over nitrate of silver. 



SUMMARY. 



From the methods already worked out as applied to the two classes 

 of mixed lards examined the following general results are deducible, 

 viz : 



The mean percentage of adulteration for the Armour samples is 37.'_'4. ' For t!ie Fiiirbauk samples 

 it is 92.10. 



It is not unusual to omit the percentage of lard stearine used in 

 accounts given by manufacturers of the extent of adulteration. If we. 

 allow that one-third of the total adulterant is lard stearine the per- 

 centages of foreign fats in the Armour and Fairbank lards are 24.83 

 and 61.40 respectively. 



In the foregoing discussion it has been assumed that the mean proper- 

 ties of a mixture of various glycerides are proportional to the quanl itiVs 

 of each present. In the case of the melting point, we know that this is 

 not the case, and the consideration of the melting point then-Ion' as a 

 factor in quantitative determinations has been omitted. It may be true 

 that other properties are also unequally developed in a mixture, and 

 this would add still another complication to the problem. 



In the present state of ourknowledge the chemist is unable to express 

 definitely the degree of adulteration which a sampleof lard has snllered. 

 He can state with confidence whether or not a given sample is adul- 



