After the four pumps have been worked for several hours by means of a steam engine of 15-horse power, and when all the oxygen has been disengaged, the pressure in the glass tube is 320 atmospheres, and the temperature at 140° below zero.
Upon suddenly opening the orifice, P, the oxygen escapes with violence, producing, in doing so, so considerable an expansion and absorption of heat as to cause a liquefied portion to appear in the glass tube, and to spirt out
from the orifice when the apparatus is sloped.
It ought to be stated that the quantity of liquefied oxygen contained in the tube one metre long and 0·01 m. in internal diameter, occupied about a third of its length, and issued from the orifice P in the form of a liquid jet.
In a communication to M. Dumas, received two days after the above sitting, M. Pictet described his experiments more fully, prefacing the account by the following very interesting remarks:—“The end to which I have been tending for the last 3 years has been to seek to demonstrate experimentally that molecular cohesion is a general property of bodies without exception.
“If the permanent gases cannot be liquefied, it must be concluded that their constituent particles do not attract each other, and are therefore independent of this law.
“To succeed experimentally in bringing the molecules of a gas into the closest possible proximity, and thus to obtain its liquefaction, certain indispensable conditions are necessary, which I thus sum up:
“1. To have a gas that must be perfectly pure and without a trace of foreign gas.
“2. To have at one’s disposal very powerful means of compression.
“3. To obtain an intense degree of cold, and the abstraction of heat at these low temperatures.