Page:The Liquefaction of Gases.djvu/43

temperature of 166° below 0°; or 60° below the temperature of the same bath at the pressure of one atmosphere, i.e. in the air. In this state the ether was very fluid, and the bath could be kept in good order for a quarter of an hour at a time.

As the exhaustion proceeded I observed the temperature of the bath and the corresponding pressure, at certain other points, of which the following may be recorded:—
The external barometer was 29.4 inches:

			inch.				Fahr.
when the mercury in the air-							°
pump barometer was			1	the bath temperature was			-106,
...	...	...	10	...	...	...	-11212,
...	...	...	20	...	...	...	-121,
...	...	...	22	...	...	...	-125,
...	...	...	24	...	...	...	-131,
...	...	...	26	...	...	...	-139,
...	...	...	27	...	...	...	-146
...	...	...	28	...	...	...	-160,
...	...	...	28.2	...	...	...	-166,

but as the thermometer takes some time to acquire the temperature of the bath, and the latter was continually falling in degree; as also the alcohol thickens considerably at the lower temperature, there is no doubt that the degrees expressed are not so low as they ought to be, perhaps even by 5° or 6° in most cases.

With dry carbonic acid under the air-pump receiver I could raise the pump barometer to twenty-nine inches when the external barometer was at thirty inches.

The arrangement by which this cooling power was combined in its effect on gases with the pressure of the pumps, was very simple in principle. An air-pump receiver open at the top was employed; the brass plate which closed the aperture had a small brass tube about six inches long, passing through it air-tight by means of a stuffing-box, so as to move easily up and down in a vertical direction. One of the glass condensing siphon tubes, already described, fig. 1, was screwed on to the lower end of the sliding tube, and the upper end of the