LARD AND LAED ADULTERATIONS. 



439 



(6) Melting point. The term melting poiut applied to a glyceride does 

 not indicate a physical state capable of being appreciated with definite- 

 ness. As usually employed it indicates the temperature at which the 

 fat becomes transparent; but this temperature, as is well known, varies 

 under certain conditions chiefly dependent upon the initial temperature 

 of the body. A more definite point, and one usually capable of being 

 ascertained, is that where a thin disk of the fat, when freed from the 

 attraction of gravitation and left to its own molecular forces, assumes a 

 sensibly spherical state. The melting point given in the following 

 analytical tables, with the exceptions to be noted, has been determined 

 by an apparatus based on the above principle. This apparatus is de- 

 scribed in the Journal of Analytical Chemistry, volume 1, part 1, pages 

 39 et seq. 



FIG. 20. 



DESCRIPTIOX OF APPARATUS. 



The apparatus, Fig. 20, consists of (1) an accurate thermometer for 

 reading easily tenths of a degree; (2) a less accurate thermometer 



