Chemistry and Physics. 187 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND PHysIcs. 
1, Liquefaction of Oxygen ;* by M. Raovut Picret.—The ob- 
ject which I have had in view for more than three years is to 
demonstrate experimentally that molecular cohesion js a general 
property of bodies, to which there is no exception. 
the permanent gases are not capable of liquefying, we must 
conclude that their constituent particles do not attract each other, 
and thus do not conform to this law. 
Thus, to cause experimentally the molecules of a gas to approach 
each other as much as possible, certain indispensable conditions 
are necessary, which may be expressed thus :— 
(1.) To have the gas absolutely pure, with no trace of foreign gas. 
ts} To be able to obtain extremely energetic pressures. 
3.) To obtain intense cold, and to subtract heat at these low 
temperatures, 
(4.) To utilise a large surface for condensation at these low tem- 
peratures, 
(5.) To be able to utilise the rapid expansion of the gas from 
extreme condensation to the atmosphere pressure—an expansion 
which, added to the preceding means, will compel liquefaction. 
Having fulfilled these five conditions, we may formulate the 
oa alternative :— 
e 
Satisfy these different conditions, and I have chosen the compli- 
cated apparatus of which the following 1s a brief description :— 
» ing E 
Couple these pumps in such a way that the exhaustion of one 
Corresponds to the compression of the other. The exhaustion ° 
the first communicates with a tube (R) of 1°1 metres long and 12° 
