394 O H an Apparatus for Gas-analysis 



tube, by interposing it at / between the two parts A and B, 

 A being for that purpose shifted to the further end of the box, 

 and the two ends of the tube in which the gas is collected con- 

 nected by vacuum- tubing, filled with mercury, with the ends 

 of the capillaries of A and B. The pressure in one side of the 

 apparatus is now reduced, either by running mercury from A 

 by means of the stopcock y, or by lowering the movable leg p 

 of B. When the points of the tube are broken the gas rushes 

 into the parts of the apparatus where the pressure is least, its 

 place being supplied by mercury from the other side. The stop- 

 cocks are then closed, the tube full of mercury removed, the 

 parts A and B reunited by/, and the analysis proceeded with. 

 When the gas is to be admitted through a, an india-rubber 

 tube is connected at y and filled with mercury by opening a, 

 as in Fig. 2, and running mercury through it. The point of 

 the collecting-tube, having previously been touched with the 

 file, is pushed into the india-rubber tube ; the other end having 

 also received a stroke of the file, is immersed in a cylinder full 

 of mercury and the lower point broken off against the bottom. 

 The mercury immediately rises in the tube; and by supplying 

 its place in the cylinder and reducing the pressure in A or B, 

 as the case may be, the whole or part of the gas may be trans- 

 ferred to the instrument. Of course in all these cases the india- 

 rubber tubes must be moistened inside with solution of corrosive 

 sublimate. 



The gas, having been introduced in one way or the other, is 

 brought all into the eudiometer q, mercury being allowed to 

 run over from A into q until the whole capillary part, down to 

 where it joins the eudiometer at g, is full of mercury, q is a 

 short eudiometer with a scale of only six divisions, like the 

 measuring-tube in Frankland's apparatus 1 . It is immersed in 

 the cylinder r, which is filled with water. The leg p is divided 

 into millimetres, and is lowered or raised until the meniscus 

 of the mercury stands exactly at one of the lines. The difference 

 in height of the two columns is then measured by means of the 



1 The tube q in the figure is shown divided as stated in the text. I have 

 found, however, that it is much more convenient to have it divided into 

 millimetres ; and the labour of calibration is no greater. 



