Page:Popular Science Monthly Volume 13.djvu/90

80 a portion of it, in the liquid state, is seen in the glass tube, and spurts out of the orifice on the apparatus being inclined.

A sufficiently clear idea of M. Pictet's method can be had from the above diagram and description; but, as yet, the reader can hardly imagine what the apparatus looks like. Fig. 2 (after a photograph)



and Fig. 3 will supply this deficiency. Fig. 2 is a general view of Pictet's grand liquefaction apparatus, as it stands in his establishment at Geneva; and Fig. 3 exhibits the same in section. This apparatus possesses considerable size; for instance, the head of a man standing would be on a level with the manometer seen near the letter H in the engraving.

The perfected apparatus as shown in Fig. 2 differs in sundry respects from the diagram Fig. 1, as will be seen at a glance. One essential difference consists in the arrangement of the liquefaction apparatus proper, Fig. 4. Here D is an iron shell (or retort), with walls 35 millimetres in thickness; it contains 700 grammes of chlorate of potash when oxygen is the gas to be liquefied. Its orifice communicates with an iron tube five metres in length, 214 millimetres internal diameter. This tube, bent as in the figure, is closed at both ends, but one end may be opened by means of the cock E. A Bourdon manometer, graduated to 800 atmospheres, shows the inside pressure. The tube c E, in which the disengaged oxygen is compressed, is completely immersed in liquid carbonic acid, which, by the mechanism of the