LARD AND LARD ADULTERATIONS. 417 



(g) Melting point of fatty acids. In couuection with the crystallizing 

 point of the fatty acids, the melting point is also of value. This tem- 

 perature has been determined in the fat acids derived from steam and 

 pure lards, and the numbers will be found in the analytical tables. In 

 the prime steam lards these numbers vary from 41.4 to 43. In pure 

 lards of other kinds the variation was from 36.9 to 46.6. 



B. CHEMICAL TROPERTIES. 



(a) Volatile acids. The quantity of volatile acid, as ordinarily esti- 

 mated in a pure lard, is quite minute. Unless some suspicion of adul- 

 teration is awakened the search for such volatile or soluble acid may be 

 omitted. Measured by the decinormal alkali solution required for 5 

 grammes of the fat the mean quantity of volatile acid in a pure lard may 

 vary from .2 to .4 of a cubic centimeter. The determination, therefore, 

 of the volatile acid in the examination of lards has none of that high 

 diagnostic value which attaches to it in the examination of butters. 



(b) Fixed acids. The quantity of fixed acids (non-volatile and insol- 

 uble in water) in lard varies from 93 to 95 per cent. 



(c) Free acids. The quantity of free acids in lard rarely exceeds .5 

 per cent. 



Twelve determinations of free acids in lards of known purity gave the 

 following numbers expressed as per cent. : 



.54 .92 .55 .75 .75 .35 .65 .60 .45 1.0 .40 .50 



(d) Saponification equivalent. The amount of caustic alkali necessary 

 to saponify the fatty acids of the common glycerides is known as its 

 sapouification equivalent or number. The operation is usually known 

 as Koettstoffer's process. The number of parts of a glyceride saponi- 

 fied by one equivalent of alkali is represented by one-third of the molec- 

 ular weight of the glyceride in question. The saponification equivalent, 

 therefore, represents the number of grams of an oil or fat saponified 

 by one equivalent in grams of an alkali. The percentage of caustic 

 potash used for saponifying a lard is about 20 and the mean sapouifica- 

 tion equivalent about 285. In the prime steam lards examined by us, 



the extreme variations were 276.14 and 290.05, and the mean 283.45. 

 In pure lards of other kinds the extremes were 272.64 and 294.14, and 

 the mean 280.33. 



(e) Iodine number The quantity of iodine absorbed by an oil or fat 

 affords one of the most valuable indications of its constitution. The 

 glycerides of the olein series have the property of absorbing the halo- 

 gens. On the other hand the glycerides of the stearic series do not 

 absorb iodine. Hence in a fat or oil from which the presence of linolein 

 and its analogous bodies can be excluded the quantity of iodine absorbed 

 may become a fairly accurate measure of the amount of oleic acid pres- 

 ent. The lard derived from different portions of the swine varies largely 

 in the amount of olein contained therein. For instance, a sample of 

 intestinal lard absorbed 57.34 per cent, of iodine ; the leaf lard from the 



17319 t. 4 2 



