[macfarlane] on the ANALYSIS OF CHEESE 5 



wide part being 65 mm. In filling it with the fibre it has been found: 

 advantageous to place a small piece of platinum or wire gauze over the 

 small opening at the bottom, to prevent the fibre from being drawn down 

 into it when the contents are being subjected to the action of the filter- 

 pump. The fibre itself is placed in the tube in successive loose layers, 

 so that they can be removed and replaced singly when desired. 



The series of operations which it seems necessary to make for ordin- 

 ary practical purposes in the analysis of cheese by the use of the appara- 

 tus just described are the following : — 



I. Water and substances volatile at 98° C. After the Macfarlane 

 tube with its crysotile contents has been dried and weighed, all the fibre 

 except the layer at the bottom is removed, and the latter pressed down 

 to such a degree of closeness as to prevent too rapid percolation. 5 

 grammes of the cheese to be examined are then mixed with part of the 

 fibre (which had been removed and placed on a sheet of glazed paper) in 

 a small mortar, and kneaded up intimately with it. This mixture is 

 introduced into the tube, the mortar carefully wiped out with a little 

 more of the weighed fibre, which is also replaced in the tube, and then 

 the whole is covered up with the fibre still remaining on the glazed 

 paper. The tube is then placed in a rack with others, and dried in the 

 water-bath at 98° C. This effects a very perfect elimination of the 

 water, owing to the fine sub-division of the particles of the cheese, and 

 the insertion of the fibre between them. This is proved by the close 

 agreement of duplicate determinations. On cooling and weighing the 

 tubes, the loss in weight indicates the quantity of moisture and volatile 

 constituents present. 



II. Butterfat and added oils. By subjecting the tube and its con- 

 tents to the action of petrolic ether of low boiling point in the above 

 described apparatus for 3 or 4 hours, all the fat is removed. The heat 

 is applied by means of a water-bath, and on this account the petrolic 

 ether should not contain any hydrocarbons of higher boiling point than 

 80° C. Of course, bisulphide of carbon or chloroform may be sub- 

 fitituted for the petrolic ether, but the latter has the advantage of cheap- 

 ness. x\fter the extraction, the tube is placed over the filter pump and 

 deprived of most of the solvent mechanically retained in it. It is then 

 placed in a tray with other tubes which have undergone the same treat- 

 ment, and heated in the water-bath for 2 hours, allowed to cool in the 

 desiccator and weighed. The loss gives the quantity of butter and other 

 fats. 



III. Alcohol Extract. — The tube is next subjected to extraction by 

 alcohol of 92 or 95 p. c. by volume. The solvent is heated by direct 

 flame, and is contained for safety's sake in a copper flask. The Stutzer 



