426 FOODS AND FOOD ADULTERANTS. 



B. CHEMICAL PROPERTIES. 



(a) Volatile acids. The remark which has been made in regard to the 

 volatile acids of pure lards and their adulterants is also applicable for 

 mixed lards. The amount is so minute as to be of no value from an 

 analytical point of view. 



(b) Saponification equivalent. The numbers representing the sapon- 

 ification equivalent do not afford any particular indication of the kind 

 of adulteration used. In the samples of Fairbank mixed lards examined 

 the mean saponification equivalent found was 279.4. In the Armour 

 samples it was 275. 



(c) Iodine number. The amount of iodine absorbed by a mixed lard 

 gives a valuable indication of the kind of the ingredients which have 

 been added to it. It has already been seen that the stearines, especially 

 those derived from tallow, have a very low iodine number, while cotton- 

 seed oil has a very high one. It is therefore possible to mix these two 

 substances together so that the resulting iodine number may be about 

 the same as that of pure lard, viz, CO per cent. In the samples of the 

 Armour mixed lards examined the mixture seems to have been made 

 in about the proportion indicated. The lowest iodine number observed 

 in these lards was 54.11 per cent., which is decidedly less than that of 

 normal pure lard. The highest number observed was 71.19 per cent. 

 The other numbers were slightly above those obtained for pure lard. 

 In the samples of mixed lards from Fairbauk & Co. the iodine numbers 

 are much higher. The lowest number observed was 78.24 and the high- 

 est 94.78 per cent. 



(d) Reaction with nitrate of silver.* Mixed lards containing cotton oil 

 show a reduction of metallic silver in a greater or less degree, accordiugto 

 the proportion of cotton oil present. In every case where cotton oil was 

 known to be present in a mixed lard this reaction was noticed. It would 

 be possible, however, to put so small a portion of cotton oil into a lard as 

 to render difficult the positive detection of it by the nitrate of silver test. 



(e) Microscopic appearances. The mixed lards, under the conditions 

 described further on, show in the field of vision of the microscope dis- 

 tinct tufted crystals of the stearines which have been used as adulter- 

 ants. The rhombic crystals of pure lard arc also often noticed in this 

 field. 



(/) Moisture in mixed lards. Mixed lards generally contain only a 

 trace of water. In one instance, however, water appears to have been 

 added as an adulterant, over 30 per cent, of it having been found. The 

 use of water as an adulterant of lard, however, is not common. 



* Later observations show that in samples kept for several months the reaction 

 with nitrate of silver is indistinct and in some cases entirely absent. 



