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XXXI. 



ON THE CONSTRUCTION OF FUME -CHAMBERS WITH 

 EFFECTIVE VENTILATION. 



By WALTER NOEL HARTLEY, D.Sc, F.R.S. 



[Plate XXXIIL] 



[Read, March 21 ; Received for Publication, March 24 ; Published, May 11, 1905.] 



The ventilation of a laboratory is as necessary for the preservation 

 of health as the ventilation of workshops for unhealthy trades. 

 Both should be provided with an enormous fresh air-supply, and 

 a continuous extraction of foul gases. The latter provision 

 necessitates very highly efficient fume-chamber ventilation, so 

 that, in fact, the fume-chambers should act as ventilating shafts 

 to the laboratory. By this it should be understood that in no 

 circumstances whatever should there be a down-draught even of a 

 momentary or temporary nature, and no escape of foul air from 

 the chamber into the laboratory even when the doors are opened. 

 A very common defect in tho ventilation of a fume-chamber is a 

 flue of dimensions which are too small, tho entrance to which is 

 wrongly placed at the top of the chamber. A second defect is 

 that the direction of the flue is not vertical. A flue constructed 

 of pipes 6 inches in diameter placed against an outside wall gives 

 rise to cooling, so that there is condensation of steam and acid 

 vapours within, which causes the dripping of condensed moisture 

 containing acid. It must be borne in mind that every bend at 

 right angles diminishes the speed of the draught by one-half ; and 

 a flue so constructed has been known to have the speed reduced 

 to -^th of that intended, solely by the introduction of six bends. 

 The net result was — 



(1) An insufficient draught, at a speed which was ineffective. 



(2) Condensation of steam and acid vapours in tho flue. 



(3) Drip of condensed water and acid, with consequent 

 corrosion and destruction of tho gas-fittings. 



SCIBNT. PROC. K.D.S., VOL. X., TAUT III. 2 F 



