12 ANALYSIS AND ADULTERATIONS OF BUTTER. 



small, as it is necessary frequently to shake the melted butter 

 so as to facilitate evaporation of the water which collects 

 below the fat. If the dish be too small and deep, the water 

 does ot evaporate at all. 



If the drying be done in the air-bath, or upon sand, as has 

 been recommended by Dr. Muter, the temperature should not 

 exceed 110 or 115 C. This plan is by far preferable, on 

 account of its rapidity and completeness. 



A quantity of about three or four grammes is sufficient, 

 provided the sample be cut from the middle of the mass 

 submitted for analysis. To take more only adds to the 

 trouble, and renders the process of drying clumsy, without 

 materially improving the result. It must be admitted that 

 not only water is volatilised during drying, but also any free 

 volatile acid which may be present ; but as the quantity 

 of free acid in even highly rancid butters is but exceedingly 

 small, this source of error may quite safely be disregarded. 



The butter thus freed from water is weighed, and the per- 

 centage of loss calculated. The fat is then again fused, and 

 dissolved in about 10 c.c. of ether. The ethereal solution of 

 fat is poured off, if the liquid be clear, into a weighed beaker, 

 or, if necessary, filtered through a weighed filter. The curd 

 and salt thus obtained are repeatedly washed with ether, 

 until a drop of the filtrate evaporated upon a glass slide no 

 longer leaves a greasy spot. The perfect removal of the fat 

 is not very easy, and a comparatively large quantity of ether 

 has to be used. The filter is dried in the water-bath, and 

 weighed between two watch-glasses, so as to prevent any 

 absorption of moisture from the atmosphere, the increase of 

 weight, added to the weight of the residue in the basin, being 

 calculated as curd and salt. 



In order to save trouble, filters, instead of being weighed, 

 are often counterbalanced by placing another filter of appa- 

 rently the same size and weight upon the opposite pan of the 



