'^0 ANALYTICAL PROCESSES. 



total solid residue, has been found to give results 0.5 

 per cent or more below the correct figure, and is there- 

 fore not described. 



Addms' Method. — This consists essentially in 

 spreading the milk over absorbent paper, drying, and 

 extracting the fat. By this means the milk is dis- 

 tributed in an extremely thin layer, and by a selective 

 action of the paper, the larger portion of the fat is left 

 on the surface. The extraction is performed by means 

 of ether, in a Soxhlet apparatus. It is essential that 

 the paper be free from matters soluble in ether. A fat- 

 free paper, manufactured by Schleicher & Schuell, is 

 obtainable in strips suitable for the purpose. Each 

 of these yields to ether from .001 to .002 gram of 

 extract, and as this would only increase the figure for 

 fat by .003 per cent., the error may be disregarded. 



The procedure is as follows : 5 c. c. of the milk are 

 discharged into a beaker 5 cm. high and 3.5 cm. in di- 

 ameter. The charged beaker is weighed, and a strip of 

 the paper which has been rolled into a coil, thrust into 

 it. In a few minutes, the paper will absorb nearly the 

 whole of the milk. The coil is then carefully withdrawn, 

 and stood dry end downward on a sheet of glass. 



With a little dexterity, all but the last fraction of a 

 drop will be absorbed by the paper. The beaker is 

 again weighed and the milk taken found by difference. 

 It is of importance to take up the whole of the milk 

 from the beaker, as the paper has a selective action, 

 removing the watery constituents by preference over 



