Page:Experimental researches in chemistry and.djvu/112

[1844 they passed, in their way from the air-holder to the pump,through a coil of thin glass tube retained in a vessel filled with a good mixture of ice and salt, and therefore at the temperatureof 0° Fahr.; the water that was condensed here was alldeposited in the first two inches of the coil.

The condensing tubes were of green bottle glass, being from $1⁄6$ to $1⁄4$ th of an inch external diameter,and from $1⁄42$ nd to $1⁄50$ th of an inch in thickness. They were chiefly of two kinds, about 11 and 9 inches in length; the one, when horizontal, havinga curve downward near one end to dip into a cold bath, and the other, being in form like an inverted siphon, could have the bend cooled also in the same manner when necessary. Into the straight part of the horizontal tube, and the longest leg of the siphon tube, pressure-gauges were introduced when required.

Caps, stopcocks and connecting pieces were employed to attach the glass tubes to the pumps, and these, being of brass, were of the usual character of those employed for operations with gas, except that they were small and carefully made. The caps were of such size that the ends

of the glass tubes entered freely into them, and had rings or a female screw worm cut in the interior, against which the cement was to adhere. The ends of the glass tubes were roughened by a file, and when a cap was to be fastened on, both it and the end of the tube were made so warm, that the cement, when applied, was thoroughly melted in contact with these parts, before the tube and cap were brought together and finally adjusted to each other. These junctions bore a pressure of thirty, forty, and fifty atmospheres, with only one failure in above one hundred instances; and that produced no complete separation of parts, but simply a small leak.

The caps, stopcocks, and connectors, screwed one into the