

BAIRD &.TATLOCK. (LONDON) LTD. 



2703 



2703 T Dr. Gibson's Improved Filtering Apparatus, as used in the University of Edinburgh, 

 complete, with indiarubber corks, etc. 



Tubulated receiver, 12 by 6| in. . . 



Brass three-way stopcock 



Long cylinder funnel . . ...... 



Short 



2704* 

 2705* 

 2706* 

 2707* 

 2708* 

 2709* 

 2710* 

 2711* 



Plain funnel, 2 in. diameter . . 

 Stand covered with indiarubber 

 Half bottle.. 

 Filter pump . . . . 



The bell-jar A (2703), rests during nitration on a square block (c) of hard mahogany, 25 centimetres square 

 and 25 millimetres thick. The cross pieces (c c) are of the same wood, and prevent warping. Over (c) is laid a 

 sheet of soft vulcanised rubber (D) of good quality, and not less than 3 millimetres thick. In the centre is a circular ' 

 disc (E) also of hard wood, 13 centimetres in diameter, and about 20 millimetres thick, which is held in position by 

 four strong brass screws, which pass down through the rubber into the square block below. In (B) is fitted a 

 single-bore rubber cork holding the brass tap (F) . This tap is simply an ordinary brass tap, converted into a three- 

 way tap by boring a hole (s) through one outer wall and through one wall of the plug. It enables the operator to 

 establish communication between (i) The bell-jar and pump ; (2) the outer air and both bell-jar and pump ; (3) 

 the outer air and pump, the bell-jar being shut off ; (4) the cuter air and bell-jar, the pump being shut off. After 

 fitting in the cork and tap, the knee-piece (H) is screwed on. If the mouth (A) be closed by a rubber stopper, and the 

 tap (F) connected by a rubber tube with a water-pump or otherexhausting apparatus, as the pressure inside diminishes, 

 the rubber sheet bulges up inside the bell-jar, and, pressing against the lower edge, closes up any interstices due to 

 irregularity on its own surface, or to imperfect grinding of the glass. A well-made water-pump will give within 

 half-an-hour a high degree of exhaustion, and this without the use of any lubricant whatever. Where a very high 

 degree of exhaustion is required, the application of a little grease outside, round the lower edge of the bell-jar, is 

 advisable. The funnel is supported by a small conical rubber stopper (i) in the upper and enlarged end of the 

 tube (K), which is in turn supported at the mouth (A) of the bell-jar by the larger rubber stopper (L). The hole in 

 this stopper should be sufficiently wide to permit of the glass tube (K) sliding easily up and down in it. The lower 

 end of the tube should be ground off at an angle, and bent as shown in the figure. It is then easy to bring the end 

 of the tube in contact with the side of the vessel in which it is desired to collect the filtrate, and thereby to entirely 

 obviate any danger of loss by spurting. 



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CROSS STREET HATTCHSr GARDETST, E-C 



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