LARD AND LARD ADULTERATIONS. 513 



lard is dissolved iu ether iu a test tube, which should be about two-thirds 

 filled. The solution should be nearly saturated. The tube is loosely 

 stopped witli cotton wool, and placed iu a quiet room, at a temperature 

 of about 60 F. When the first crystals are formed they are removed by 

 means of a pipette, placed on the slide of the microscope, and examined 

 iu the usual way. The forms of the crystals produced have already 

 been described. 



David Wesson* says of Belfield's microscopic test, that while at times 

 it gives very characteristic crystals, at other times their forms are not 

 sufficiently definite to be relied upon. The nitric and sulphuric acid 

 tests are sometimes unreliable, especially with old samples. Bechi's test 

 is also sometimes uncertain. On old samples of cotton oil it sometimes' 

 gives negative results, while with old samples of lard oil it will give a 

 slight reduction. 



Michael Conroyt uses the following tests for the determination of the 

 purity of a sample of lard. 



(1) Heat and stir about one-half ounce of lard with one-tenth its 

 weight of strong nitric acid, specific gravity 1.42, in a porcelain dish 

 of about 8 ounces capacity, until a brisk action commences, when the 

 source of heat should be removed. Pure lard sets in about one hour to 

 a pale orange-colored solid, but if it contain cotton oil it takes a more or 

 less deep orange-brown tint. 



(2) The test of Labiche was also tried, as follows : Equal parts of the 

 fat and neutral acetate of lead and ammonia added, stirring briskly. 

 The acetate of lead decomposes and the nascent oxide reacts upon the 

 oil, causing it to turn red. This reaction proved a failure. 



(3) The proceeding of Ernest Milliau By this test it is claimed 1 per 

 cent, of cotton oil can be detected. 



(4) Bechi's test: When sodium carbonate has been used to correct 

 the acidity of lard this test is not applicable, unless the re agent be 

 acidified with nitric acid. The following modification of Bechi's test 

 was employed : A solution of five parts of silver nitrate and one part of 

 nitric acid, specific gravity 1.42, in one hundred parts of alcohol. Put 

 grams of lard in a ilry test tube and add one-fourth gram of the so- 

 lution above described, and hold the tube in boiling water for five min- 

 utes. Pure lard remains perfectly white, but if adulterated with cotton 

 oil it assumes a more or less olive-brown color. This color is best ob- 

 served when the lard sets. One percent, of cotton oil in a lard gave a 

 color quite distinct from the genuine article. 



Cotton oil has also been used for the adulteration of tallow.J 

 The melting-point of the genuine tallow, according to Williams, va- 

 ries considerably in different samples, ranging from 100 to 120 F. 



" The Analyst, July, 1888, p. 140. 



tThe Analyst, Vol. I!?, No. 151, p. 203. The Pliarmacentical Journal and Transac- 

 tions, -Seplomhor 22, 1383, p. 237. 



t Kola ml Williams, Journal of Society of Chemical Industry, March, 1888, p. 186. 

 17319 pt. 4 8 



