( 124 ) 
we meet with the difficulty that the terms containing the second 
powers of those corrections cannot be neglected in comparison with 
the terms containing the first power, because although each of these 
are much larger, they yet partia!ly neutralize each other. A calcula- 
tion in which the terms mentioned were kept, did not give a good 
result. Therefore by means of the value of 4, derived by approxima- 
tion from @, / and y, viz. b— 0.0009, I have calculated the cor- 
rection term, which VAN DER WAALS’ formula requires in addition 
to the terms used, viz. ATL? d? (1—bd), subtracted this value from 
PV and have equalized the derived value to @' + /’'d + y'd?, from 
which is found: 
M= |B Ups yor 
(7 == 0.000670, 
vy’ = 0.00000088. 
By putting: 
pe RT, 
PS RTba;, 
== RD, 
we find: 
a = 0.00030, ma = 0.000042, 
b—=0.00091, ms = 0.00004, 
Finally let us compare our results with those of ReanauLT and 
AmAGAT. The values determined by me are indicated in the figure 
by circles, those found by RecNnavLt by squares; in this I have 
supposed that at the lowest pressure REGNAULT's result and mine 
were the same; after this the other points have been drawn. 
From a development in series, calculated from AMAGAT’s obser- 
vations at 0°, 15°.4 and 47.°3 C., we find by means of interpolation: 
PV_,° — 1.07252 + 0.000719 4 0.00000067 
20 : V V2 ; 
If we substitute V = 0.01129, Amacat’s greatest volume at 
15°.5 C. we find PVsge = 1.1414 (PVj;°., = 1.1290), while from 
the values of «, /? and y we obtain PV,,° = 1.1394 and from the 
original equation of VAN DER WAALS with the given values of 
a and 6: PVge = 1.1401. 
