ESTIMATION or FAT — ADAMs' METHOD. 10, 



paid to the estimation of fat in milk than that of any other 

 constituent. The methods are very numerous, and mav con- 

 veniently be divided into three classes : — 



(1) Gravimetric methods, in which the fat is separated from 

 the milk by a suitable solvent, and weighed after evaporation of 

 the solvent. 



(2) Volumetric methods, in which the fat is separated from 

 the milk by suitable means, and its volume measured. 



(3) Indirect methods, in which the amount of fat is deduced 

 from the determination of some physical property. 



Of these methods the gravimetric methods are undoubtedly 

 the most accurate, though they are all to a certain extent tedious 

 and not capable of use by unskilled persons. 



The solvent chiefly used for extracting the fat is ether, which 

 is convenient on account of the low boiling point and heat of 

 volatilisation, its great solvent power for fat, and its comparative 

 great miscibility with water, which renders it unnecessary to 

 have the milk solids in a state of absolute dryness. 



Petroleum ether, chloroform, carbon disulphide, benzene, 

 carbon tetrachloride, and amyl alcohol liave also been used, but, 

 though they give the same results, are not so convenient. 



(1) Gravimetric Methods. 



The leading gi-avimetric methods are discussed in the following 

 pages; on the whole the Gottlieb method is the best, though 

 those due to Adams, Storch, Wernei-Schmid, and Bell are little, 

 if at all, inferior in accuracy. 



The Adams Method. — Dr. il. A. Adams, Public Analyst 

 for Kent, was led to devise this method from his observation 

 that when milk was dropped on blotting-paper, it spread out to 

 a much greater extent than was possible in a basin, flask, or 

 even on a flat surface of glass ; he was of opinion that extraction 

 of fat by ether would be much more complete. 



As originally designed, the method was as follows : — Strips of 

 white blotting-paper, "' mill 428," ih inches wide by 22 inches long, 

 were coiled up loosely and held by having a brass ring shpped 

 over them. These were dried at 100" C. to constant weight, 

 the weighings being performed in a weighing bottle to prevent 

 absorption of moisture from the atmosphere. Five c.c. of milk 

 was pipetted out into a small beaker and the weight noted ; 

 one of the coils was dropped in and the milk absorbed as com- 

 pletely as possible by the blotting-paper. When sbsorptiou was 

 complete, the coil was carefully removed and stood, dry end 

 downwards, on a gla,ss plate, the beaker being again weighed 

 and the quantity of milk taken up by the coil found from the 



