510 FOODS AND FOOD ADULTERANTS. 



Milliau's modification is recommended, but it is advised that a blank 

 experiment be made with the re agent, since sometimes alcohol contains 

 impurities which reduce silver nitrate. Experiments in the use of the 

 silver nitrate test for quantitative purposes did not give satisfactory re- 

 sults. 



Jones* says that he was the first public analyst of England to cer. 

 tify a case of lard adulterated with cotton oil under the sale of food and 

 drugs act. He first applied a qualitative test with chloride of sulphur 

 essentially the process described by Warren. He used 5 grams of 

 the fluid lard in a porcelain dish, to which he adds 2cc of equal vol- 

 umes of chloride of sulphur and bisulphide of carbon. The mixture is 

 well stirred at first and occasionally for fifteen or twenty minutes. No 

 heat is applied. By this treatment genuine lard only thickens or be- 

 comes rather stiff in three hours. If it contain cotton oil it becomes 

 quite hard and solid in one-half hour. This test is very simple, but 

 with practice one can with certainty pick out all lards containing cot- 

 ton oil. He estimates the extent of the adulteration by the percentage 

 of iodine absorbed. He finds that pure lard never takes sensibly more 

 than GO per cent, of iodine, while cotton oil takes 105 to 110 per cent. 

 He adopts the formula 



100 r L ^sorbed-GO x per ^ cotton Qi , 



The accuracy of the work is checked by the specific gravity taken at 

 100 F. At this temperature the specific gravity of pure lard is taken 

 at .90GO, and of cotton oil at .9135. 



The formula for calculating the percentage of adulteration by the 

 specific gravity is as follows : 



100 / Sp.gr. found- 906 x =pcr ^ ^^ ojl 

 V. / .o J 



The radical error in the method of Mr. Jones is, that he takes no ac- 

 count whatever of the admixture of stearine with adulterated lard, which 

 may be done so skillfully as to wholly vitiate the method employed for 

 determining the amount of adulteration. 



Stock t describes a modification of Milliau's method for the detection 

 of cotton oM. His method is as follows : 



Fifteen grams of the sample are saponified in a 7 inch porcelain basin 

 with a mixture of 15cc of .'50 per cent. NallO and 15cc of 92 per cent, 

 alcohol. To commence, the t'at is heated to 110 0. The alkaline al- 

 cohol must be added in quantities not exceeding lee :it a time, the 



*Tho Aualyst, Sept ember 1H-S, v . 170. 

 tTbo Analyst, September, 18^8, p. 172. 



