LARD AND LARD ADULTERATIONS. 509 



Hebner* states that in Bechi's test, without impairment of the deli- 

 cacy, the re-agent may be made up without the amyl alcohol or rape-seed 

 oil. lie makes the solution of nitrate of silver in alcohol and ether very 

 slightly acidified, and adds to the oil to be examined about one-half of 

 the bulk of the silver solution, and then heats on the water-bath for one- 

 quarter of an hour longer. Pure lard always remains perfectly un- 

 changed by this treatment, while cotton-oil mixtures blacken more or 

 less quickly. It is quite possible to arrive at approximate quantitative 

 results by comparing the oil mixtures of known composition. Mr. 

 Hehner does not see any advantage in Milliau's modification. The rise 

 of temperature when mixed with sulphuric acid is to be preferred as a 

 method of estimating the quantity of cotton oil in lard. The sample, 

 of course, must be free from water. When 50 grams of pure lard, ac- 

 cording to Hehner, are mixed with lOcc of strong sulphuric acid the 

 rise of temperature varies from 24 to 27.5, while cotton oil in the 

 same conditions shows an increase of 70. In every case lard which re- 

 duces silver shows an increase of temperature of more than 27.5. 



[JSToTE. Compare these temperatures with those obtained in our ex- 

 periments. The mean rise of temperature for pure lard was 41.5, and 

 the mean increase for cotton oil 85.4.] 



Kolaml Williams! has also contributed a study to the adulteration of 

 lard with cotton oil. He regards the saponification equivalent as quite 

 useless as far as the detection of cotton oil in lard is concerned, as both 

 the lard and cotton oil require practically the same amount ef aikali for 

 saponiftcatiou. In case of the use of cocoa-nut oil, however, the deter- 

 mination of the saponification equivalent is of the highest importance. 



The melting-point also is regarded as of no value in respect of the de- 

 tection of adulteration, since it depends largely on the parts of the ani- 

 mal from which the fat has been obtained. The specific gravity of 

 pure lard at the boiling-point of water is about .861, and of cotton-oil 

 at the same temperature .872. It may be possible, therefore, to derive 

 some valuable information in regard to the constitution of lard or 

 mixed lards from a careful determination of the specific gravity. Mr. 

 Williams failed to obtain valuable results with Maumeiie's test. This 

 failure was doubtless due to some imperfection in the method of ma- 

 nipulation. 



lu the absence of interfering boilies Mr. Williams relies chiefly upon 

 the percentage of iodine absorbed in estimating approximately tho 

 amount of cotton oil present as an adulterant. The addition of stea- 

 riue to lard interferes seriously with the determination of the percent- 

 age of added cotton oil by the iodine method. He has found pure 

 lards to absorb from GO to G2 per cent, of iodine. One sample of lard, 

 said to be leaf lard, absorbed only 51 per cent. Some leaf lard ren- 

 dered by Mr. Allen himself absorbed 51.8 per cent. 



*Tko Analyst, September 1888, p. 165, ct seq, 

 tThe Analyst, September, 1888, pp. 168,169. 



