( 243 ) 
who ascribes, therefore, the appearance of this type to abnormality. 
The occurrence of two heterogeneous double plaitpoints R 1 and R\ 
by the side of the open plait C 0 R t A is, indeed, not very probable, 
nor do any theoretical or experimental grounds plead in favour oi 
the existence of such a system of plaits. That, however, van Laar s 
original, type II, Buchner’s type I, fig. 3 here, is very well possible 
for normal substances, van der Waals’s theoretical investigations and 
Buchner’s experimental ones have proved convincingly. 
8. Classification of the investigated systems. 
All the systems mentioned in the table appear to belong to the 
types I, 2, or 3, except one single system, methyl alcohol and ethane, 
which may possibly belong to type 5. 
For normal components we have found type I for nitro-benzene 
and aniline with saturated hydro-carbons, a few times also the case 
of lig. 2 a (SO, with hexane); the cases of CO, with little volatile 
substances, chrysene and ether, etc. found by Buchner, belong to 
type 3. \ 
We have not met with the case 26 for normal substances, nor 
can we state with certainty that we have found it for abnormal 
substances, for on account of the very high pressures which soon 
occur, the plaitpoint line cannot be examined far enough. But if we 
compare inter se the results which a series of homologous hydro¬ 
carbons with methyl alcohol give, the supposition suggests itself that 
we have to do here with a transition of case 26 to 2 a, passing 
from the lower to the higher hydro-carbons. 
For while for propane and methyl alcohol according to the obser¬ 
vations of Kuenen the — is — 0°,12 starting from the critical end- 
dp 
point (so we have here case 1 or 26), this value changes to —0°,03 
at about 100 Atm., which certainly agrees better with 26. (See table II). 
For isobutane x ) and methyl alcohol the — is at first practically 
speaking- 0, at 10 or at 70 atms. we find no perceptible difference 
for the plaitpoint temperature; if the pressure is increased further, 
the temperature too begins to rise very perceptibly, and + 0.009 
is found for — at 140 atm. (See table II). So we are forced to conclude 
__ d P 
J >^The~preparations of butane and isobutane were particularly pure; they had 
been presented to us by Mr. Ouedinoff at Brussels, for which we once more 
express our thanks to him. 
