DAIRY PRODUCTS. 59 



chloric acid, using' pheuol-phthalein as an indicator. The number of 

 cubic centimeters of the acid used for the sample deducted from the 

 number required for the blank gives the number of cubic centimeters 

 which combines with the fat, and the saturation equivalent is calculated 

 by the following formula, in which W equals the weight of fat taken 

 in milligrams and N the number of cubic centimeters which has com- 

 bined with the fat. 



2 W 

 Sat. Equiv. = M~ 



For pure butters the mean value of N" is about 17 when 2.5 grams of 

 butter fat are taken, and the saturation equivalent may vary from 230 

 to 255. On the other hand for lards, tallows, and other fats commonly 

 used for adulterants the equivalent; rises to 270 and 200. These num- 

 bers, therefore, give a fair idea of the purity of a butter, or if an adul- 

 teration has been practiced, of its extent. 



ESTIMATION OF INSOLUBLE ACIDS IN BUTTER FAT. 



Method of Helmcr. 1 This method consists in saponifying the fat with 

 alcoholic caustic potash, subsequent evaporation of the alcohol, decom- 

 position of the soap with sulphuric or hydrochloric acid, and the deter- 

 mination of the insoluble acid graviinctrically. 



The process as originally described by Hehner is carried on as fol- 

 lows : 



The filtered butter fat is weighed in a beaker glass with a glass rod ; 

 3 or 4 grams are taken out by means of the glass rod and put in an 

 evaporating dish about 5 inches in diameter; the glass rod with the fat 

 which remains on it is left in the evaporating dish. The beaker glass 

 is again weighed and the amount of butter fat determined from the 

 difference in weight. To the weighed fat are added 50cc. alcohol and 1 to 

 2 grams of pure caustic potash. The alcohol is warmed gradually upon 

 the water bath, by which the butter fat, especially when stirred with 

 the glass rod, easily dissolves to a clear yellow liquid, giving off a dis- 

 tinct odor of butyric ether. The heating is continued for about five 

 minutes and distilled water is then added drop by drop to the mass. 

 If this produces a cloudiness in the liquid, due to the separation of un- 

 decornposed fat, the heating is continued somewhat longer until finally 

 the further addition of water does not produce the least cloudiness. 

 Should, however, through the careless addition of water, some fat sepa- 

 rate in the form of oily drops which do not again easily pass into the 

 solution in the diluted alcohol, the whole mass must be evaporated to 

 dryuess and treated anew with alcohol, or the experiment be done over 

 again with some fresh fat. 



The clear soap solution is now evaporated on the water bath to the 

 consistency of sirup in order to remove the alcohol, and the residue 



Zeit. Anal. Chcm. 1877, pp. 145 ct scq. 



