LVIIIL—AN IMPROVED METHOD FOR DETERMINING THE 
GASES DISSOLVED IN WATER, sy RICHARD J. 
MOSS, F.c.s. 
(Read, January 20th, 1879.] 
Havina had occasion to determine the quantity and composition 
of the gases dissolved in certain waters with a high degree of 
accuracy, I found it impossible to get satisfactory results by the 
ordinary methods, and accordingly attempted to devise some 
more trustworthy method. The common plan of collecting the 
gases from a measured quantity of water in a tube from which 
the air is expelled by boiling water in it is very simple, and 
sufficiently accurate for most purposes. A great improvement in 
this method (Watts’ Dictionary, Vol. V., p. 1,028), consists mainly 
in the employment of a long collecting tube so arranged that one 
end dips into mercury, which ascends in the tube when the air 
is expelled by vapour of water, a Torricellian vacuum is thus 
obtained into which the gases are allowed to escape. The gases 
collected by either of these methods must be subsequently 
transferred to a suitable vessel for measurement and for analysis. 
Whichever method is employed there is no convenient way of 
ascertaining, (1) whether throughout the operation the joints of 
the apparatus remain perfectly air-tight, (2) whether the space 
into which the gases are allowed to escape is quite free from air, 
and, (3) whether the gases are completely expelled from the liquid 
under examination. The employment of the Sprengel pump 
overcomes all these difficulties and offers so many obvious 
advantages that I should suppose its use has long ago been 
suggested. I have, however, failed to find any published account 
of such an application of that useful apparatus, and as the form 
of apparatus which I| have finally adopted has proved satisfactory, 
I venture to describe it, in the hope that it may contribute 
towards increased precision in the methods of water analysis. 
