MILK AND MILK PRODUCTS 13 



should be used, and one should be extracted without any milk 

 on it, as a tare for the others. Four or five hours' extraction 

 is necessary, and the coils should be well dried before extraction 

 is begun. 



Thimble- shaped cases made of fat-free paper are now ob- 

 tainable and are convenient for holding the absorbent material 

 on which the milk is spread. The fine texture prevents un- 

 dissolved matter escaping. A case may be used repeatedly. 

 Sour milk may be thinned with ammonium hydroxid before 

 taking the portion for analysis. 



Babcock Asbestos Method. This is recommended by the A. O- 

 A. C. : Provide a hollow cylinder of perforated sheet metal 60 

 mm. long and 20 mm. in diameter, closed 5 mm. from one end 

 by a disk of the same material. The perforations should be 

 about 0.7 mm. in diameter and 0.7 mm. apart. Fill the cylin- 

 der loosely with from 1.5 to 2.5 grams of freshly ignited woolly 

 asbestos free from fine or brittle material. Cool in a desiccator 

 and weigh. Introduce a weighed quantity of milk (about 4 

 grams) and dry at 100. The cylinder is placed in the ex- 

 traction tube and extracted with ether in the usual way. The 

 ether is evaporated and the fat weighed. The extracted cyl- 

 inder may be dried at 100 and the fat checked by the loss in 

 weight. A higher degree of accuracy is secured by performing 

 the drying operation in hydrogen. 



For thorough extraction, especially with difficultly soluble 

 materials and volatile solvents, the continuous extraction ap- 

 paratus devised by Szombathy, but commonly called the Soxh- 

 let tube, is most suitable. 



The apparatus, as shown in figure i, is provided with a 

 globular metal condenser, but any form may be employed. 

 The material may be placed in a fat-free paper thimble and 

 covered with a plug of cotton to prevent loss of fine particles. 

 In place of the cotton plug, a Gooch crucible may be used ? 

 as shown in the cut, The top of the thimble should be a short 



