960 
ox = 20 the diminution becomes extremely small, pointing to con- 
stancy at still lower densities. Argon differs from isopentane, how- 
ever, in this respect that with argon at higher densities far above 
on = 265, the increase becomes still more rapid, while the behaviour 
of isopentane would lead one to expect a diminution in the rate of 
increase. 
From his observations upon isopentane Youre!) deduced the following 
3 ‚ : dp 
rule for the behaviour of amen 
( y 
Be B) 
dp 
(55) 20 | 
Ou? v> tv, 
This rule has already been contirmed for a variety of substances, 
and is, as far as its second part is concerned, also obeyed by argon. 
For carbon dioxide, ethylene and isopentane, RrINGANUM found 
Op 
that the quantity an —= z()- P| vis a minimum for v about 
C U 
En and at temperatures about 10° above ¢,. If the law of corre- 
sponding states were strictly true this minimum for argon should be 
at on = 380, and therefore outside the region of experiment. Nothing 
can be done consequently beyond trying to judge from extrapolation, 
if, and where, the minimum exists. If for this purpose we graph 
ar as a function of ey at —122° and —116°, then extrapolation 
towards higher densities shows that it is probable that these curves 
3 
would also exhibit a minimum for argon at v= z 
Physics. — “On the rectilinear diameter for argon.” By E. Manas, 
H. KAMERLINGH Onnes, and C. A. CROMMELIN. Comm. 1314 
from the physical Laboratory at Leiden. (Continued). 
(Communicated in the meeting of November 1912). 
§ 5. Results. The results obtained are given in the following 
table np 901): 
The calculated values of the ordinates of the diameter given in 
this table have been obtained from the equation 
Dor = 0.20956 — 0.00 26235 t, K): 
Nl 
*) For the notations, see Suppl. No. 23. 
