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Art. IX. — Description a Variation in ifie Form of Bent 
Tuhes^ formerly described^ for experimenting on small cpian~> 
tities*(f Gases. By Mr William Kerr. Communicated by 
the Author. 
In a recent communication * I described a simple form of a bent 
tube, very convenient for the collection and absorption of small 
quantities of gas. In the present paper, I beg leave to lay be- 
fore the public the account of an apparatus, which differs in 
some respects from the former, but by which the gas evolved, 
at any period of an experiment, may be examined, unmixed 
with atmospheric air, without diluting the liquid in the appara- 
tus, or in any manner disturbing the experiment going on. Thi& 
apparatus is also a bent tube, and differs from my former in 
being open at both ends, and in having the second branch, or 
that corresponding to the shut branch of the tube formerly de- 
scribed, bent downwards a little above its middle, at an angle 
somewhat greater than that formed by the inclination of the two 
branches. In Fig. 7., Plate VII., A is the first branch, or that 
through which the materials are most conveniently introduced ; 
B represents the ascending part of the second branch, and C the 
descending part of the same branch, which can be shut at its 
inferior end by the stopper D, or by cork coated with wax, ta 
resist the action of acids. 
When this tube is to be used, the extremity of the descend- 
ing part of the second branch must first be shut by a stopper or 
cork, and the liquid poured into the first branch, till it has oc- 
cupied the whole of the second. This may easily be done by a 
little address, in nearly the same manner as was described in my 
former communication, for filling a bent tube of the simplest 
form. The tube is now to be placed so, that its first angle shall 
be its lowest point, when the solid substance to be acted on is 
to be dropped into the open end of the first branch. This body _ 
will slide down to the lowest point, and, owing to the construc- 
tion of this part of the tube being the same as that of the tube 
formerly described, the gas evolved will rise into the ascending 
• Page 53, of this volume. 
