Page:Popular Science Monthly Volume 13.djvu/91

This page has been validated.

pumps before described, enters the apparatus at a and passes out as vapor from the orifice b, after volatilization.

PSM V13 D091 Sectional view of the pictet apparatus.jpg
Fig. 3.—Section of the Same.
B, cast-iron shell containing chlorate of potash; A A', closed iron tube in which the gas is condensed; C, refrigerating cylinder in which liquid carbonic acid is volatilized; F, wooden case packed with some bad heat-conductor; D, reservoir holding liquid carbonic acid, surrounded by a refrigerating cylinder in which liquid sulphurous acid is volatilized; H, case packed with a bad heat-conductor; G, gasometer containing gaseous carbonic acid; K, reservoir for liquid sulphurous acid; P, one of the double-action pumps; A', cock which can be opened so as to give an exit to the liquefied gas which escapes in the direction shown by the arrows.

With this apparatus, M. Raoul Pictet, on Monday, December 24, 1877, in the presence of members of the Physical Society of Geneva, three different times obtained violent jets of vapor which contained globules of liquefied oxygen. On the following Thursday the experiment was made for the fourth time. The manometer, which had risen to 560 atmospheres, after a few minutes fell to 505, and there stood for

PSM V13 D091 Retort and the tube in which gas is liquefied.jpg
Fig. 4.—The Retort and the Tube in which the Gas is liquefied.

over half an hour, showing by this diminution of pressure the transition of a portion of the gas into the liquid state, under the influence of the -140° temperature to which it was subjected. The cock closing the orifice of the tube was then opened, and a jet of oxygen escaped with extraordinary violence. A beam of electric light, projected on the cone of escapement, enabled the spectators to see that the jet consisted of two distinct parts: the one central, a few centimetres in length, whose white color gave evidence of liquid or even solid elements; the other external, whose blue color showed the return of the compressed and frozen oxygen to the gaseous state.

In later experiments M. Pictet succeeded in collecting a very appreciable volume of liquid oxygen, and in liquefying all the other "permanent" gases.