DAIRY PRODUCTS. 87 



The fat is dissolved by ether or petroleum, collected in a weighed 

 flask, and, after thorough drying, weighed. I have already mentioned 

 that by the use of asbestos paper I had hoped to be able to estimate 

 the moisture in milk, but so far have not achieved the success which I 

 believe is possible. 



Of all the methods for the gravimetric determinations of fat in milk, 

 I do not hesitate to say that the Adams method, properly carried out, 

 is the best. 



SOXHLET'S AREOMETRIC METHOD OF ESTIMATING FAT IN MILK. 1 



Caldwell and Parr 2 call attention to the difficulty which is often ex- 

 perienced in using Soxhlet's areoinetric method for the estimation of 

 fat in milk. They say, speaking of the determination of fat by the 

 lactobutyrometer : "But in this case, while the butyrometer gave tol- 

 erable results, Soxhlet's method failed entirely ;. even after standing 

 five hours the layer of ether fat solution in the mixing bottle, which 

 should be over a centimeter thick, was hardly a millimeter thick." 



This experience is so much in harmony with my own that I thought 

 it would be of interest to call attention to some of the difficulties en- 

 countered in working with Soxhlet's method. 



Soxhlet's original paper was published in " Zeitschrift des Land- 

 wirthschaftlichen Vereins in Bayern," in 1880. 



It rests upon the assumption that an alkaline milk shaken with ether 

 will give all its fat to the ether, and this solution, being lighter than 

 the rest of the mixture, will collect at the top, where it can be sepa- 

 rated and its specific gravity determined. 



The reagents used are ether saturated with water and a solution of 

 caustic 'potash containing 400 grams to the litre. 



The milk and reagents having been brought to a temperature of 17.5 

 C. are measured into a flask (I use an ordinary pint beer bottle), with 

 pipettes furnished with the apparatus; 200cc. milk, lOcc. of potash solu- 

 tion, and uoc~:. of the aqueous ether are the quantities to be employed. 

 The milk is first placed in the flask and to this the potash solution 

 added and shaken vigorously. Afterwards the ether is added and the 

 shaking continued for one minute longer. The bottle is then put into 

 water at a temperature of 17.5 C. and gently struck on the table in a ver- 

 tical position at intervals of half a minute for fifteen or twenty minutes. 

 At the end of this time the ether-fat solution has collected at the top, 

 wheuce it is passed to the areoinetric cylinder by means of the rubber 

 bulb blowing apparatus shown in figure 1. 



Water is now added at a temperature of 16 C. to 18 C. to the outer 

 cylinder, and after the temperature has become constant the density of 

 the ethereal solui ion is read on the scale of the areometer. At the same 

 time the temperature is read from the delicate thermometer attached 



1 H. W. Wiley, Journal of Analytical Chemistry, vol. 1, no. g, 

 i. Chein. Jour., vol. 7, p. 245. 



