68 



J. W. Evans — Apparatus for Isolating Minerals. 



B represents a long glass tube (b^ passing through the centre of 

 a cork. At the lower end the tube is brought to a blunt point, in. 

 which is a minute aperture. After being drawn out to a point, the 

 end must be carefully heated again so as to thicken the glass round 

 the hole without closing it entirely. Unless this is done, the point 

 of the tube is apt to break off. This tube can be closed above by 

 india-rubber tubing and a short piece of glass rod. The cork is also 

 perforated (as shown) by another tube (63), which can be closed in 

 a similar manner. 



ill 





^ ■ ;Scal& of Ccnti -merrea . 



The liquid and the material to be operated on are placed in the 

 funnel. When the first separation has taken place, the apparatus B 

 is inserted, the point of h^ should reach down close to the pinchcock. 

 \ is left open at the top, and h^ is connected with an air-pump, 

 which should be very cautiously worked and the pressure diminished 

 so that a gentle stream of bubbles passes from the opening at the 

 end of &!• The particles are thus thoroughlj^ shaken ; the lighter 

 fragments that have been carried with the heavier, or vice versa, are 

 disengaged. 



The upper end of h^ is now closed and the air is exhausted so as 

 to get rid of any air attached to the grains. The apparatus may 

 then be separated from the air-pump by compressing the india- 

 rubber tube attached to h.^ and at the same time disconnecting the 



