ANALYSIS OF MILK. 



37 



into a smal], tared, porcelain dish, covered and weighed ; a drop of acetic acid is added, and 

 the dish is placed on the water bath. The milk coagulates, and as it dries the solids are 

 kept in a finely divided condition by occasional stirring. As the solids are approaching 

 dryness, i.e., in about an hour, they must be almost constantly stirred and rubbed with a 

 glass rod for about ten minutes, and the result is a white residue, resembling flour, which 

 is scraped off the dish into a filter, put into a Soxhlet and extracted with dry ether or light 

 petroleum (gasoline), boiling under 50" C. for between two and three hours. The ether or 

 gasoline is distilled off from the fat, and the latter dried to constant weight. 



The following table gives the fat determination of six milks, the numbers in the first 

 column were obtained by Mr. Babington, using the method just described, and those in 

 the second column by myself, from the same milk, by boiling up with ether in a residue 

 not granulated and without the use of the Soxhlet : — 



The celebrated Manchester milk case, where a certificate of Mr. Estcourt was disputed 

 on the ground that the solids not fat of genuine milk might fall below 9 per cent., led to 

 the appointment of a committee of the Society of Public Analysts to reconsider the whole 

 question of milk analysis. This was the more needful, as the process adopted by the 

 chemists at Somerset House was not that in use by analysts generally, and their standards 

 were not those of the Society, a state of things that can not be looked upon as otherwise 

 than unfortunate. Their process was that of drying the total solids to constant weight, 

 and evaporating the portion of milk destined for fat determination only to a paste, and 



