o- 



66 ANALYSIS AND ADULTERATIONS OP BUTTER. 



Dr. Dupr6's highly interesting experiments {Analyst, 

 1876, page 87) were conducted according to two separate 

 plans. Butter-fat, when heated with water for four or five 

 hours in a sealed tube to 260° or 290° C, spUts up into 

 glycerine, soluble acids, and insoluble acids. A strong silver 

 tube, with screw ends, was employed, about 5 grammes of 

 fat being decomposed in each experiment. " After cooling 

 the tube was opened, and the contents Trashed into a beaker, 

 or latterly a flask, as recommended by Dr. Muter, and the 

 insoluble fatty acids thoroughly washed, dried, and weighed, 

 without removing them from the flask or beaker. The 

 silver tube was washed out with ether, and the amount of 

 fatty acids thus obtained added to that found as above. The 

 aqueous filtrate containing the soluble fatty acids and the 

 glycerine was neutralised with barium carbonate, boiled, 

 filtered, and evaporated, at first on a water-bath, finally 

 in vacuo over oil of vitrei. The residue obtained was then 

 weighed, and the glycerine present extracted with alcohol, 

 or expelled by prolonged heating to a temperature of 

 130° C, and the rest again weighed, the loss being taken as 

 glycerine. Finally, the residual barium salt was converted 

 into sulphate, from which the amount of soluble acids 

 present could be calculated. Neither of these processes is, 

 however, quite satisfactory ; in the first some barium salt is 

 dissolved by the alcohol ; in the second the glycerine cannot 

 be all expelled without danger of decomposing some of the 

 barium salt. 



" The general results of these experiments, I have already 

 stated, viz., that they show the presence of a notable 

 proportion of soluble fatty acids." Dr. Dupri5, in four 

 experiments made on difl:erent butters thus obtained 5' 3, 

 6'4, 5'33, and 5'8 per cent., mean of the four, 6'70per cent., 

 and glycerine on an average 11 '69 per cent. 



The second process adopted by Dr. DuprI, which he 



