274 DR. R. ANGUS SMITH ON AN APPARATUS FOR 



one piece with the tube (d). The tube (b) is a receiver for 

 the gases, and is connected by a flexible tube to the small 

 tube projecting from (</). This tube may be disconnected 

 by means of an external pressure valve, or a steel spring, 

 which closes the caoutchouc tube. A similar valve is placed 

 at the upper part of the tube (b). 



If the balloon be strong and sufficiently elastic, it may be 

 pressed flat, and then allowed to expand, when it will fill 

 itself if the end of the tube has been dipped into any liquid. 

 When raised again into its proper position, the water may be 

 pressed from the balloon into the flask, and up to the point 

 (a). The balloon is then empty, or nearly so, and perfectly 

 flat. If it be strong, or if it have a tendency to expand, it 

 may exercise a slight pressure, tending of course to draw air 

 into the joints, but this is very small indeed, and if too much, 

 then a balloon with less elasticity may be used. The joint 

 (a) is shut, and that between (b) and (d) opened. The water 

 is boiled, and the air as it rises passes into the upper tube 

 (b). The balloon (c) is constantly expanding and contract- 

 ing to a small extent. The hot water is continually rising, 

 but has no injurious effiect on the balloon. It is important 

 not to allow it to hang down, as cold water may lodge in 

 it. The apparatus is small, holding about 3,300 grains of 

 water. Much less may in reality be used with safety. The 

 tube (d) is wide, of about |in. bore, and so is more readily 

 kept at a high heat during the process. When no more air 

 escapes the connecting valve is shut, the tube (b) removed, 

 and the gas passed into a graduated tube over mercury for 

 measurement and analysis. 



When the gas fills (b), there is little fear of loss by absorp- 

 tion. This absorption may be calculated, or it may be entirely 

 prevented by completely separating the gas from the water. 

 This is done by putting a piece of paraffine into the tube ; 

 it melts, swims on the top, and on cooling prevents all con- 

 nection between the water and the air or gas in (b). Paraf- 



