ANALYTIC PROCESSES 1 7 



continuous extraction apparatus devised by 

 Szombathy, but commonly called the Soxhlet 

 tube, is most suitable. 



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 porcelain or platinum Gooch 

 crucible may be used, as shown in the cut. 

 The top of the thimble should be a short dis- 

 tance below, and the top of the crucible a short 

 distance above, the bend of the siphon. The 

 thimble should be supported by a section of 

 glass tubing, i to 2 cm. long, with rounded 

 edges; the edge on which the thimble rests should 

 be a little uneven to prevent a close joint, which 

 would hinder the siphoning of some of the 

 liquid. 



Alundum cylinders will probably be useful. 



Loss of solvent by leakage often occurs. It 

 may be diminished somewhat by soaking the 

 corks in rather strong hot gelatin solution, 

 draining them quickly and then exposing them 

 for some hours to formaldehyde vapor. 



The solvents most generally employed are 

 ether and petroleum spirit, but carbon tetra- 

 chlorid is well adapted for extraction purposes 

 as it has high solvent power for fats and is not 

 easily inflammable. 



When extraction is completed, the carton and 



