422 FOODS AND FOOD ADULTERANTS. 



A. PHYSICAL PROPERTIES. 



(a) Specific gravity. The specific gravity of stearines may be taken 

 in their solid state or in a liquid state at a high temperature, 40 to 100. 



(6) Melting point. The melting points of the stearines are higher 

 than the natural glycerides from which they are derived. A prime oleo- 

 stearine from Armour & Co., Chicago, showed a melting point of 51.9. 

 A prime lard stearine from the same firm showed a melting point of 

 44.3, which is only slightly higher than the mean melting point of pure 

 lards. The lowest melting point of any stearine examined was a sample 

 of dead-hog stearine from J. P. Squire, Boston, which was 33.2. The 

 highest observed melting point in the stearines examined was an oleo- 

 stearine from N. K. Fairbank & Co., Chicago, showing 53.8. The high 

 melting point of the stearines is a characteristic of great value in the 

 adulteration of lard since it serves to counteract the influence of the 

 cotton oil, which of course tends to lower the melting point of any lard 

 mixture into which it may enter. The influence of the various con- 

 stituents, however, on the melting point does not seem to be propor- 

 tional to the respective quantity of each therein. For instance, a mix- 

 ture of 25 per cent, of cotton oil having a melting point below zero, with 

 25 per cent, of an oleo-stearine having a melting point of only about 

 12 above the normal for pure lard, with 50 per cent, of pure lard of 

 normal melting point, might not show a lowering of the melting point 

 at all proportional to the presumable influence of the cotton oil present. 

 The cotton-oil stearine, as might be expected, has a melting point be- 

 low that of the similar products derived from lard and tallow. 



(c) Color reaction. The color reactions produced in the steariues by 

 sulphuric and nitric acids are much the same as those produced in the 

 original glycerides from which they were derived. Cotton-oil stearine 

 shows a less intense color perhaps than ths original oil; while in the 

 case of tallow and lard stearines the coloration is not marked enough to 

 be susceptible of description. 



(d) Refractive index. The refractive index of the stearines appears 

 to be slightly lower than that of the original glycerides. The high re- 

 fractive index which was noticed in the case of the original glycerides 

 of the cotton-oil was also found in the stearine from that source. 



(<?) Rise of temperature with sulphuric acid. With the lard and tallow 

 stearines no degree of comparison can be made in the rise of tempera- 

 ture with that produced in the original glycerides, on account of the 

 high initial temperature which is necessary for the conduct of the ex- 

 periment. Allowing for the difference in initial temperature, however, 

 the steariues deport themselves very much as the original glycerides. 



B. CHEMICAL PROPERTIES. 



(a) Volatile acids. The amount of volatile acids in the stearines 

 mentioned is so small as to be- negligible. 



