«38 



HYGROMETER TOR GASSESf. 



Description 

 of it. 



of it to those, who are aware that in these delicate experi-* 

 nients we have never too many means of securing ourselves 

 against the errours of manipulation. 



This apparatus being intended to be introduced, very 

 accurately closed, under a receiver the mouth of which i» 

 immersed in mercury, it must be mounted wholly in iron. 

 When the vessel is carried above the level of the mercury, 

 it is easy to open it, to give an opportunity for the mutual 

 action of the substance it contains and the gas under the 

 receiver ; which is effected by moving the dependent part of 

 the counterpoise, previously disengaging the catch. To 

 keep it in this position, nothing is required but a simple 

 wooden bracket, with a notch cut in it to receive the handle 

 of the instrument, in which it is fixed by a wedge. After 

 having allowed it to stay as long as is necessary for the action 

 required to take place, the glass vessel may be closed by its 

 glass stopple, and taken out of the trough, without danger 

 of tfny thing escaping from it, or of a single particle of mer- 

 cury getting in, by means of the same catch, which is 

 placed in the middle of the counterpoise, and strongly presses 

 down the cover. 



To examine the hygrometrical state of any gas, take the 

 glass bottle out of its collar, weigh it accurately, and till it 

 with dry pulverized muriate of lime, that has been in fusion ; 

 which likewise must be weighed. Having replaced it, and 

 shiU down the cover close, introduce it under the receiver, 

 and then raise the cover. The weight gained by the mu- 

 ' riate of lime will indicate the quantity of water absorbed. 



Explanation of the figures. 

 Explanation of PI. VI II, fig. 1, represents the apparatus introduced under 

 the plate. ^.j^^ receiver, the glass stopple raised by the hinged cover, 

 to which it i& cemented. The cover is kept up by the catch 

 g; which in this situation is placed under ihe cross part of 

 the handle. This figure is on a scale of t\vo lines to an inch, 

 English measure. 



In fig. 2 the essential parts of the instrument are shown 

 on a scale of four lines to an inch. 



^ is a t;lass bottle, holding two or three centilitres, the 

 Tn9Uth of which is ground perfectly even ; and confined by 

 th^ screw d in the collar B, which opens with a joint at C, 



so 



Method of 

 using it. 



