76 Dr. Hare's Improved Eudiometers. 
three tubes are pasielty at with water, as represented » 
in the drawing (Ws fig. 4) When the passage between the 5 
gauge and the reeipient is open, if. the pressure on the in- 
cluded air be more or Jess than that of the atmosphere, the > 
water will rise in one of the gauge tubes, and sink in the 
other. Other liquids may be substituted for water, in the - 
gau.e. when de irable.. 
In addition to the principal collar. of leathers, and screws » 
for rendering that collar compact, there isin the’ mercurial 
FKudiometers, a smail hollow cylinder, (a sine ofa aie 
rel,) with au additional collar of cork for confining oil about . 
the rod, where it enters the collar of leathers; otherwtse in | 
operating with mereury, the leathers soon become so dry as.« 
fo permit air or mereury to pass by the ro 
dit may be proper to point out, that in operations with, the - 
hydro-oxygen Eudiometer, accurate measurement is necessa~ 
ry, only, with respect to one of the gases. In analyzing an ~ 
inflammable gas by oxygen gas, or oxygen by hydrogen gas, 
it is Only necessary that “the quantity of the gas. which is to. 
be.analyzed, and the deficit caused by the explosion, should. 
be ascertained with accuracy. . The other. gas, wh must — 
he used i in excess, sometintes greater, sometimes less, must, — 
in using the Mercurial Eudiometer, be made to occupy the | 
gauge. In analyzing the air, or any mixture containing 
oxygen, the gauge is filled with hydrogen gas, as already 
stated ; but, mm examinng inflammable gas, the atmospheric 
air may be ‘left in the gauge, as its only active qualities are 
those of oxygen gas 
Figs. 6 and 7 represent those forms of the sliding-rod 
Eudiometer, which I have found most serviceable for experi- 
ments: with nitric oxide gas; with the solutions of sulphurets 5 
or those of sulphate, or muriate of irun, saturated with nitri¢ 
: Fig. 6 
