£58 Mr. Pepys’ Account of a new Eudiometer. 
acid gas, and the oxygene gas, leaving only such residual gas 
as the oxygene might have originally contained. 
Transferring is not here necessary, as the two solutions 
may be used one after the other, taking care to use the solution 
of green sulphate last. 
Where it is not requisite to transfer the gas into a dried or 
clean measure, previous to the use of another solution, as in the 
instance I have just mentioned, a quantity of the first solution 
may be withdrawn, by simply filling the elastic bottle with 
mercury, then joining it to the measure, and by inclining the 
measure, the mercury by its gravity will displace the former 
solution. 
If at any time the gas should get drawn into the elastic 
bottle, it may be very easily returned into the measure, by 
inclining sometimes the bottle, and sometimes the measure. 
The only error that could arise from this is, an increase of 
temperature in the gas, which may be rectified, by plunging 
the whole apparatus into mercury or water, of the standard 
temperature. 
The advantages of this construction of the eudiometer, will 
be readily perceived by all those who are in the habit of mak- 
ing chemical experiments. The portion of gas to be examined 
is completely under command ; it may be agitated without 
the least fear of the intrusion of any atmospheric air, and 
the process thereby very materially shortened. The gum 
elastic is a substance so little acted upon by chemical agents, 
that a great variety may be employed ; and above all, we can 
very conveniently use hot solutions, which will be found an 
important auxiliary in the examination of some compound 
gases. 
