REPORT OP THE CHEMIST. 283 



the flask is broken tip with a glass rod and allowed to drop into a 

 weighed dish, together with whatever is readily detached from the 

 filter paper. The funnel with the filter paper is then placed in the 

 flask, a hole made in the point of the paper, and tlie remaining par- 

 ticles washed into the flask with abs(dute alcohol delivered from a 

 small wash bottle. After dissolving up all the particles left in the 

 flask by the same solvent, it is poured into the dish containing the rest 

 of the insoluble acid, and the flask rinsed out with another small por- 

 tion of absolute alcohol. This dissolves the fatty acids nearly as 

 rapidly as ether, and is not so volatile, besides serving the purpose 

 of aiding in driving off the water from the acids, Avhen drying. The 

 dish is now placed in a steam-jacketed air bath and kept at a temper- 

 ature of 100° C. for about 2 hours after the alcohol has been all 

 driven off. After cooling and weighing, it is again dried for two 

 hours longer. If not over 10 to 15 milligrams have been lost it is 

 not dried further; otherwise it is dried for another hour. The dish 

 is then weighed, the original weight of the dish subtracted, and the 

 percentage of insoluble acid determined by dividing its weight by the 

 weight of the fat taken. The percentage of insoluble acid in a pure 

 butter is about 88. In some rare samples it may reach 89, but in such 

 a case there are grave grounds for suspicion. Lards, tallows, &c., 

 on the contrary, have from 92 to 94 of insoluble acid. 

 The second chemical method in use is known as 



koettstorfer's process. 



About 2. 5 grams butter fat (filtered and free from water) are weighed 

 into a patent rubber-stoppered bottle, and 25 cubic centimeters ai^ir'Qx- 

 imately semi-normal alcoholic potash added. The exact amount taken 

 is determined by weighing a small pipette with the beaker of fat, run- 

 ning the fat into the bottle from the pipette, and weighing beaker and 

 pipette again. The alcoholic potash is measured always in the same 

 pipette and uniformity further insured by always allowing it to drain 

 the same length of time (30 seconds). The bottle is then placed in the 

 steam bath, together with a blank, containing no fat. After saponi- 

 fication is complete and the bottles cooled down, the contents are 

 titrated with accurately semi-normal hydrochloric acid, using phenol- 

 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 ^vith the 

 fat, and the saturation equivalent is calculated by the following form- 

 ula, in which. W equals the weight of fat taken in milligrams, and 

 N the number of cubic centimeters which has combined with the fat: 



Sat. Equiv. =-^ 



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 com- 

 monly used for adulterants the equivalent rises to 270 to 290. These 

 numbers, therefore, give a fair idea of the purity of a butter, or, if 

 an adulteration has been practiced, of its extent. 



The third chemical process used has for its object the determina- 

 tion of the volatile acids present in a fat. Although not an absolute 

 method, yet it has met with great favor among analysts. 



