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Dr. Hare’s improved. Eudiometers. ea 
_ CHEMISTRY, PHYSICS, MECHANICS, &e: 
Ane. 1X.—An Accouat of some Eudiometers of an Impr 
* Construction.. By Rosert Hare, M. D. Professor of 
Chemistry in the University of Pennsylvania. — . 
In the ‘dacoud volume of the American Journal of Science, 
T published an aceount of some Eudiometers, operating by a 
meehanism which, previously, had not been employed in Eu- 
_ diometry. A graduated rod, sliding intoa tube through a col- 
lar of leathers, soaked in lard, and compressed by a screw. 
so as to be perfectly air tight, was employed to vary the ca- 
pacity of the tube, and at the same time to be a measure of 
the quantity of air, or of any other gas, consequently drawn 
in or expelled. About one-third of the tube was occupied 
ay the sliding rod. The remainder, being recurved, and 
converging to a perforated apex, was of a form convenient for 
withdrawing measured portions of gas from vessels inverted 
over water, or mercury. 
ere were two forms of the sliding rod Eudiometer, one 
designed to be used with nitric oxide, or with liquids absorb- 
ing oxygen; the other, with explosive mixtures. The latter 
differed from the. Eudiometers for explosive mixtures previ- 
ously invented, in the ¢ontrivance for exploding the gases, as 
well as in the mode for measuring them; a wire ignited by 
galvanism being substituted for the electric spark, as the 
-means of infammation. 
T now send you drawings of several Eudiometers, operating 
upon the principle of those above alluded to, with some mod- 
ifications suggested by experience. Fig. 1. represents a 
hydro-oxygen Eudiometer, in which the measurements ate 
made by a sliding rod, and the explosions are effected by the 
galvanic ignition of a platina wire, as in an instrument former- 
ly described, excepting, that the method then employed of 
cementing the platina wire, in holes made through the glasg, 
