86 FOODS AND FOOD ADULTERANTS. 



placing each witliiu a brass ring as it is rolled, inscribing on one corner with a lead 

 pencil its own proper number. 



These coils are next thoroughly dried, and I need hardly say the accuracy of the 

 process depends upon this drying. This can be satisfactorily done in an ordinary 

 air bath at 100 C., providing the bath be heated properly and the paper kept in it 

 long enough. I found the common way of heating the thin bottom of the bath with 

 a single jet not to answer. My bath is placed upon a stout iron surface, which is 

 heated by a large ring of jets; in this way the heat is evenly distributed over the 

 whole of the bottom of the bath, and the papers, which are put' in a cage frame of 

 tinned iron wire 5 by 2^ inches and divided into eight partitions, get evenly and com- 

 pletely dried, if allowed to remain in the bath all night, and weighed in a weighing- 

 tube next morning, and their weights having been registered according to their 

 numbers, stored away ready for use, as follows : 



The milk to be examined is shaken, and with a pipette 5cc. are discharged into a 

 small beaker 2 inches high by 1 diameter, of a capacity of about SOce. weighing about 

 12 grams. This charged beaker is first weighed, and then a paper coil gently thrust 

 into the milk very nearly to the bottom. In a few minutes the paper sucks up nearly 

 the whole of the milk. The paper is then carefully withdrawn by the dry extremity 

 of the coil and gently reversed, and stood, dry end downwards, on a clean sheet of 

 glass. With a little dexterity all but the last fraction of a drop can be removed from 

 the beaker and got on the paper. The beaker is again weighed, and the milk taken 

 got by difference. It is of importance to take up the whole of the milk from the 

 beaker, as I am disposed to consider the paper has a selective action, removing the 

 watery constituents of the milk by preference over the fat. 



The charged paper is next placed in the water oven on the glass plate milk-end 

 upwards, and rough-dried. Mismanagement may possibly cause a drop to pass down 

 through the coil onto the glass. This accident ought never to occur; but if it does, 

 it is revealed in a moment by inspection of the surface of the glass, and the experi- 

 ment is thereby lost. 



In about an hour it is rough-dried and in a suitable condition for the extraction of 

 the fat. 



The method of Adams has been thoroughly tried by the English 

 chemists, and has received the approval of the English Society of Pub- 

 lic Analysts. It gives uniformly about .2 per cent, more fat in normal 

 milk than the ordinary gravimetric methods. 



In this laboratory we use the following modification of the process : 



The blotting paper is replaced by thick filtering paper cut into strips 

 2 feet long and 2.5 in. wide. These are thoroughly extracted by ether or 

 petroleum. 



One end of the strip of paper being held horizontally by a clamp or 

 by an assistant, 5cc. milk is run out by a pipette from a weighing bottle 

 along the middle of the strip of filtering paper, being careful not to let 

 the milk get too near the ends of the paper, and to secure an even dis- 

 tribution of it over the whole length of the slip. The pipette is re- 

 placed in the weighing bottle and the whole reweighed, and thus the 

 quantity of milk taken is accurately determined. The strip of paper is 

 now hung up over a sand bath in an inclosed space high enough to re- 

 ceive it where the air has a, temperature of 100 C. (circa). In two or three 

 minutes the paper is thoroughly dry. It is at once, while still hot, 

 rolled into a coil and placed before cooling in the extraction apparatus 

 already described. 



