LARD AND LARD ADULTERATIONS. 473 



Now, a mixed lard whose iodine equivalent is about 64 per cent. (Ar- 

 mour's) can not be made of any considerable quantity of the above mixt- 

 ure and pure lard. It must contain a notable quantity of lard stearine. 



For example : 



40 parts of cotton oil and oleo-stearine at 74 = 2960 

 30 parts of 1 ard at 62 = 1860 



30 parts of lard stearine at 47 = 1410 



100 parts =6230 



The theoretical iodine number of such a compound lard is therefore 

 62.30 per cent. The above hypothetical example, in the light of the 

 analyses made, shows approximately the composition of a compound 

 lard whose iodine number is not above 63 per cent. 



In the Fairbank samples the mean iodine number is 85.31 per cent. 

 The microscope revealed also the presence of oleo-steariue in these 

 samples. They were presumably composed of cotton oil, lard, and oleo- 

 stearines, and perhaps some lard. As was shown by the specific grav- 

 ity they contained an excess of cotton oil. These mixtures may be rep- 

 resented by the following proportions : 



10 parts oleo-stearine at 20 = 200 



25 parts lard stearine at 47 = 1175 

 65 parts cotton oil at 109=7085 



100 parts =8460 



Theoretical iodine number = 84.60 per cent. 



No formulae can be given for computing the proportions of ingre- 

 dients from the quantity of iodine absorbed, except in the tentative 

 way indicated above, but the value of the iodine number, when thus 

 studied with other quantitative data, is sufficiently illustrated. 



(6) By calculation from the refractive indeJC.^-Sorne valuable infor- 

 mation concerning the quantitative composition of a mixed lard may be 

 derive.d from a study of the refractive index. 



The mean refractive index at 25 of the samples of lard examined is 

 1.4620; water at the same temperature showing 1.3300 5 for cotton oil 

 the number is 1.4674; for oleo stearine, 1.4582; for lard stearine, 1.4594. 



The determination of a much larger number of samples of the stear- 

 mes would be desirable before deciding on a permanent standard, but 

 the above numbers will serve provisionally. 



Points. 



. Difference between lard and cotton oil -(-54 



Difference between lard and oleo stear i ne .' 38 



Difference between lard and lard steariue 24 



It thus appears that the addition of cotton oil to a lard would raise 

 its refractive index, while the addition of the stearines would lower it. 



