FIG. 2. Modified form of flask. 



Two holes in the neck of the flask effectually overcame the trouble, 

 besides making possible other valuable improvements in the apparatus. 

 Figure 2 shows the flask with the holes. It will be noticed that the 

 amount of ether collected in the space C when the flask with this modi- 

 fication is used is much less, making a saving of about 10 cc in each 

 extraction. 



The holes are about one-fourth of an inch in diameter and are placed 



opposite each other at a distance approxi- 

 mately one-fourth of an inch above the up- 

 per mercury line or above the line of the 

 trough. 



The second and third difficulties were 

 overcome by means of a simple spring 

 shown in figures 3 and 4, a description of 

 the spring and its uses being given in the 

 following paragraphs. 



It is well known to all who have used the 

 Knorr ether extraction apparatus that the 

 sample and sometimes layers of asbestos are 

 pushed up toward the top of the tube by 



the expansion of the air and ether vapor which they inclose. Not 

 only is there danger of losing in this way the sample for the crude 

 fiber determination, but there is a chance of foreign substances 

 reaching the interior of the fat flask, and the cushion formed 

 of air, ether vapor, or both, materially checks the ether and extract 

 on their way to the flask. This, as one can readily see, prevents 

 thorough extraction, 

 even though the sam- 

 ple be not pushed 

 over the top of the 

 extraction tube. 



The remedy hith- 

 erto employed con- 

 sists in striking 

 gently the portion of 

 the condenser sur- 

 rounding the tube, 

 at the same time 

 holding the flask to 

 prevent breaking. 

 As a rule this serves 

 to break up the cushion of air, but it is often necessary to remove 

 the tube from the condenser and push down the sample with a stirring 

 rod. Every time a tube is taken from the condenser there is danger 

 of mercury getting into the fat flask, despite the best precautions. 



[Cir. 69] 



FIG. 3. Perspective drawing of spring. 



