Even after the sample has been restored to its proper place in the tube 

 by either of the foregoing methods, the cushion of vapor is likely to 

 form again, requiring a repetition of the procedure just described. 



A simple spring was, therefore, designed to avoid this unnecessary 

 care and loss of time. It is made of No. 19 spring brass wire, and is of 

 the form shown in the perspective drawing, figure 3. The parts consist 

 of the upright B, at the lower end of which is formed the open equi- 

 lateral triangle T. At the top of B the wire is bent 

 into a single coil C and extended in the portion Z>, the 

 end of which is bent at Eto facilitate inserting it in 

 the tube. A slight double curve should be given to B, 

 as illustrated in the drawings, so that the points X 

 and J^shall be in contact with the sides of the tube, 

 thereby holding the apparatus in a vertical position. 



The plane of the triangle T 7 should be perpendicular 

 to B. The length of its sides will vary according to 

 the inside diameter of the extraction tube and should 

 be such as will allow a slight amount 

 of pla} T . The plane in which B and 

 D lie must bisect the angle A to in- 

 sure an upright position of the appa- 

 ratus in the tube. 



To use this apparatus proceed as 

 follows: 



Drop a perforated platinum (or 

 nickel) disk on top of the sample so 

 that it will lie in a horizontal posi- 

 tion. Press B and D between the 

 t, thumb and forefinger and push the 



T 



\ 



FIG. 4. Spring in 

 position in tube. 



spring down into the tube until T presses firmly 

 against the disk; in fact it does no harm to compress 

 the sample slightly. The complete combination is 

 shown in figure 4, being the sample and P the 

 disk. D presses firmly against the side of the tube, 

 thereby holding the apparatus securely in place at 

 any height. 



B should have a length of about 50 mm, and D 

 40 mm, the loop C being 15 mm in diameter. It is 

 not necessary to use exactly these dimensions, but 

 care should be taken to have C below the top of the 

 extraction tube, otherwise the ether in falling from the condenser may 

 strike the wire and be scattered over the side of the tube. 



With flasks modified as described it is possible to use the form of 

 tube shown in figure 5. The advantages of this tube over the old form 

 are many. (1) The initial cost is much less, since for most solvents 



[Cir. 69] 



PIG. 5. New form of 

 extraction tube, a, 

 Perforated disk; 6, 

 Wire riveted to disk; 

 c, Size i inch. 



