52 ANALYSIS AND ADULTERATIONS OF BUTTER. 



this case an additional quantity of alcohol may effect the 

 solution, frequently only after the liquid has been concen- 

 trated by evaporation, but it is preferable to begin the 

 experiment afresh with a new quantity of butter-fat. 



The soap is then heated on the water-bath until all smell 

 of alcohol has disappeared ; the dish is nearly filled with 

 water, in which the gelatinous soap, which has separated on 

 concentrating the liquid, readily dissolves. Dilute hydro- 

 chloric acid is now added to strong acid reaction of the 

 liquid, to liberate the fatty acids. These rise quickly to the 

 surface as a white or yellowish creamy precipitate, whilst a 

 strong disagreeable smell of butyric acid or its relations is 

 given off. It will be observed, that unless the alcohol be 

 removed completely, or very nearly so, the risk of losing 

 some of the fatty acids is caused by their being kept dissolved 

 in the alcohol. 



The separated fatty acids are heated on the water-bath for 

 about half-an-hour, until they are perfectly fused into a clear 

 oil, and until the acid liquid below is nearly clear. During 

 the process of fusion it is well to avoid allowing the water 

 to evaporate much, as by so doing the acids come into imme- 

 diate contact with the dry dish, and can be removed only 

 with considerable difficulty. The water in the water-bath 

 should not be boiling. 



Meanwhile a filter of about five inches in diameter, of the 

 best and closest Swedish filter paper, has been dried in the 

 water-box, as well as a filter weighing-tube with ground 

 stopper, and a small beaker. The beaker, the filter-tube, and 

 the tube and filter, are now weighed, the weight of the beaker 

 plus filter being thus obtained. The paper, on account of its 

 being eminently hygroscopic, cannot of course be weighed 

 directly, but must be enclosed in the tube, or between two 

 watch-glasses. It is equally inadmissible to counterpoise it 

 by another filter of the same size and paper, as is frequently 



