Adeney — An Apparatus for Gas Analysis, 8fc. 549 



forward, and then lowering the vessel slightly to loosen its connec- 

 tion with the tube g. If the reservoir has been previously- 

 adjusted to the level of the end of the tube g, immediately on 

 loosening its connection with the vessel in the manner described, 

 the bubbles of air will escape into the atmosphere. After the 

 laboratory vessel has been finally placed in position, a mercury 

 trough filled with water, and supported on an ordinary table 

 support, is placed under the vessel, and fixed at such a height 

 that the lower end of the vessel is immersed in the water. This 

 arrangement prevents leakage or diffusion of air through the 

 indiarubber cork which closes the end of the vessel. 



When the combustion of the water residue has been completed, 

 the combustion tube is again exhausted, and the gases resulting 

 from the combustion are transferred to the laboratory vessel ; this 

 operation being completed, the gases are next passed into the 

 burette to be measured. 



The method of adjusting the level of the mercury in the 

 burette, after the gases have been passed into it, will require some 

 explanation. The simple plan of closing the stopcock, and then 

 raising and lowering the reservoir, in order to bring the mercury 

 to the level of the division line selected for measurement, cannot 

 be followed, since after transferring the gas, a small bubble of it 

 remains in the laboratory vessel under the indiarubber collar 

 attached to the tube g, and cannot be expelled. When therefore 

 the level of the mercury in the burette is being adjusted, the 

 connection between the burette and laboratory vessel must be left 

 open, and the adjustment be made by working the two reservoirs 

 conjointly. To transfer in the first instance the gases into the 

 burette from the laboratory vessel, the reservoir of the former is 

 lowered, and that of the latter raised, until nearly all the gas has 

 passed over, a little however still remaining in the laboratory 

 vessel. The operator at this point must observe whether the 

 gases will require to be compressed or expanded, in order that the 

 mercury in the burette shall stand after final adjustment, at the 

 level of the division line selected for measurement, and in order 

 that, at the same time, the laboratory vessel shall be completely 

 filled with mercury, with the exception, of course, of the space 

 occupied by the small bubble above referred to. With a little 

 practice, the final adjustment may be effected in a few seconds. 



