Issued March 14, 1911. 



United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 69. 



xl 



H. W. WILEY, Chief of Bureau. 



IMPROVEMENTS IN THE KNORR FAT 



By H. L. WALTER and C. E. GOODRICH, Assistant Chemists, Miscellaneous Division. 



The common form of Knorr extraction apparatus presents a few 

 difficulties in manipulation, some of which the authors have effectively 

 overcome. These difficulties are: 



(1) In many cases the ether which condenses in the lower part of 

 the condenser can not return freely to the flask because the extraction 

 tube fits too snugly in the mouth of the flask. In this case all the 

 ether soon collects in the space C, figure 1, and 



the flask becomes dry. 



(2) There is a tendency for many of the samples, 

 together with layers of the asbestos felt, to push 

 upward in the tube by the expansion of air and 

 ether vapor which they inclose. 



(3) When a sample is very fluffy, as alfalfas, for 

 example, the ether runs through so rapidty that it 

 fails to reach all parts of the sample, and conse- 

 quently gives a poor extraction. 



(4) The form of extraction tube ordinarily em- 

 ployed has several disadvantages which will be 

 discussed later. 



The first of these difficulties was overcome as 

 follows: A glance at figure 1 will show that the 

 escape of ether vapor from the flask of the Knorr 

 extraction apparatus is accomplished by support- 

 ing the tube A upon the flask by means of three 

 glass projections D on the lower part of the 

 tube, which raise it somewhat above the rim 

 of the flask. This is easily accomplished, even 

 though only a small space is left between the 

 flask and the tube, but those who- have used the tube to any extent 

 know that considerable ether condenses in the lower part of the con- 

 denser and soon fills the space C above the mercury seal. After enough 

 has condensed to reach the top of the flask, the ether begins to flow 

 back into it. To take care of this return flow is very difficult, and in 

 many cases impossible, without using some other means to support the 

 extraction tube. 



FIG. 1. Old form of Knorr 

 extraction apparatus. 



JTo insure the free use of this invention to the public, letters patent have been applied for. 

 78931 Cir. C9 11 



