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RAIRD &T\TLOCK (LONDON) LTD. 



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2196 



2197 



By George Stanley 



2196 Gas Drying Apparatus, for use with a mechanical exhaust pump. 

 Walpole, Esq. With stand 



It is found convenient in chemical laboratories to use a mechanical exhaust pump for many purposes, especially 

 in conjunction with distillation apparatus. To maintain the pump in such a condition that at any moment it is 

 capable of working at its maximum efficiency, it must be kept dry by use of either a steam-jacket or else an efficient 

 drying apparatus interposed between it and the still. 



The accompanying drawing represents a form of desiccator which has been in use continuously for some 

 months under somewhat severe conditions. 



The gases from the still pass directly down the tower (A). If the tap (E) be closed and (F) open, they pass 

 through the concentrated sulphuric acid in the reservoir (B). This is the arrangement when the still is being 

 exhausted at the commencement of distillation or when only a moderate vacuum is required. If the tap (F) is 

 closed and (E) opened, the gases pass up the tower, meeting a slow stream of sulphuric acid running over the glass 

 beads and regulated by tap (c). 



In this arrangement a short circuit is thus established which eliminates the hydrostatic pressure of the sul- 

 phuric acid in the bottle (B), and there is no resistance offered to the gases passing to the pump. It is advisable 

 to leave all taps turned off when the apparatus is not in use. The acid from (B) can be run out periodically, and if 

 suitable, used again. 



3197 Gas Drying Apparatus, with two calcium chloride drying towers, 16 in. high, two J-litre 

 gas washing bottles, and two 12-in. U tubes, fitted with I.R. stoppers, and glass stopcocks 

 as figured, on polished board 



A2197 Gas Absorption Apparatus (Potash) . . . , . . . . . . each 



The gas enters through the admission tube (A) into the potash lye in the interior of the apparatus, and passes 

 through the " glass-wool " (B) saturated with potash lye. The latter is kept by spike-like glass projections (c) 

 at some height above the potash lye below, so that undisturbed observation of the gas bubbles passing through 

 is assured. The gas, completely freed from carbonic acid, takes its course through tube (D) and a thick layer of 

 soda lime, with which the inner part of the apparatus is charged, to the exit tube (E) . The great length of this soda- 

 line tube ensures, even with very rapid working of the analysis, the gas being completely dried passing from the 

 potash lye. All the faults are avoided which are otherwise likely to occur if rubber or ground glass joints are 

 employed. 



2198 Gas Absorption Apparatus (Sulphuric Acid) . . . . . . . . each 



This apparatus serves for absorption of water, in place of the chloride of calcium tubes commonly used. The 

 liquid is conveyed into the apparatus through tube (A), and only requires renewal after it has been used about 

 twenty-five times. The interior (A) and (B) of the apparatus is filled with glass-wool, and as much sulphuric acid 

 as will suffice for saturating the glass-wool. The bulk of the water formed is condensed in (A), and, after 

 weighing, can be easily removed through the admission tube, in order to keep the sulphuric acid as nearly as 

 possible anhydrous. 





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