68 ANALYSIS AND ADULTERATIONS OF BUTTER. 



Dr. Muter came to the same conclusion as did Dr. Dupre", 

 the method employed by him being a far more indirect one, 

 and certainly less accurate. A comparatively large quantity 

 of butter-fat, ten grammes, was saponified in an open flask 

 by means of alcoholic potash, and the soap decomposed by 

 the addition of sulphuric acid, the alcohol having been 

 previously driven off. The insoluble fatty acids were washed 

 in the flask, dried, and weighed. The liquid containing the 

 soluble fatty acids was made up to 1,000 c.c. In one portion 

 the total acidity was determined, due to free sulphuric and 

 soluble fatty acids. In a second portion the total amount of 

 sulphuric acid, both free and combined, was precipitated by 

 means of chloride of barium, the precipitated sulphate being 

 collected and weighed as usual. Lastly, a third quantity 

 was evaporated, the free sulphuric acid driven off by 

 strongly heating the residue, the mineral matter being taken 

 as sulphate of potash. From these last two data the amount 

 of acidity due to free sulphuric acid was ascertained, which, 

 subtracted from the total acidity, yielded the proportion of 

 acidity due to soluble butter acids. 



It will be observed that this process is in several points 

 open to objection, inasmuch as a portion of the volatile acids 

 is necessarily lost in the form of butyric ether during saponi- 

 fication in the open flask, and as the residue calculated as 

 sulphate of potash is never of sufficient purity to allow of 

 its being taken as such. But these objections might easily 

 be avoided by saponifying in a closed flask and determining 

 by precipitation the proportion of sulphuric acid in the 

 residue obtained by evaporation. There are, however, graver 

 objections inseparable from the process, namely three different 

 determinations, gravimetrically and volumetrically, involving 

 a great many different manipulations, have to be made, and 

 small figures, obtained by subtracting comparatively large 

 amounts from each other, be calculated as volatile acids. 



