The American journal of science and arts . mode of ignition may be preferable, because an elec-trophorus is more portable than a galvanic apparatus. In damp weather, or in a laboratory where there is a pneu-matic cistern, or amid the moisture arising from the respira-tion of a large class, it is often impossible to accomplish ex-plosions by electricity. 72 Dr. Hareh Improved Eudiometers^ Op the Mercurial Sliding Rod Eudiometer, with a-Water Gauge. The Eudiometer which 1 have des ribed, though satisfac-tory in its results, and in its conveniency, when used withwater, has not been found so when
The American journal of science and arts . mode of ignition may be preferable, because an elec-trophorus is more portable than a galvanic apparatus. In damp weather, or in a laboratory where there is a pneu-matic cistern, or amid the moisture arising from the respira-tion of a large class, it is often impossible to accomplish ex-plosions by electricity. 72 Dr. Hareh Improved Eudiometers^ Op the Mercurial Sliding Rod Eudiometer, with a-Water Gauge. The Eudiometer which 1 have des ribed, though satisfac-tory in its results, and in its conveniency, when used withwater, has not been found so when used over mercury. Thegreat weight of this fluid caused the indications to vary in con-sequence of variations of position, during manipulation, tooslight to be avoided. The instrument represented in the fol-lowi ig rut, (fig, 4.) is furnished with a water gauge, whichbeing appealed to, enables us to render the density of thegases within, in equilibrio with the air without. Hence wecan effect their measurement with great accuFacy. Fig. Dr, Harems Improved Eudiemeters^ 73 Let us suppose that this Eudiometer has been thoroughlyfilled with mercury, the sliding rod being drawn out to itsgreatest extent; and that it is firmlj fixeu over a mercurialeistern in the position in which it is represented in the draw-ing, the little funnel-shaped part at the bottom, descendinginto the fluid to the depth of half an inch Above this partis seen a cock (C), the key of which, in addition to the per-foration usual in cocks, has another, at right angles to, andterminating in, the ordinary perforation. When the lever(L) attached to the key of this cock is situated as ilis seen in the drawing, the tube conlaining the slidingrod communicates with the recipient, but not with the mer-cury of the reservoir. Supposing the lever moved through aquarter of a circle, to the other side of the glass, the tube inwhich the rod slides, will communicate at the same time withthe recipient and the reservoir. By m
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