(4) 
The preceding tables are obtained by interpolation. Varying 
quantities of phenol are added to mixtures of water and acetone 
containing 1.83, 4.24, 7.94, 15.6, 24.6, 31.8, 40.4, 50.2, 59.9 and 
64.9 percent of acetone, and the temperature was determined at which 
the two liquid phases which form are converted into a single phase. 
Let us now examine the different connodal lines in figure |. 
Below 68° they terminate in two points on the side W-Ph. of the 
triangle; these two points represent two binary solutions which are 
in equilibrium with each other. The positions of the conjugate points 
on the connodal line itself is still unknown. At 68° the connodal 
line touches the side W. Ph. in a point, at which the two hquid 
phases of the binary system W. Ph. become identical. As is shown 
in the figure at 80°, 85° and 87°, the connodal lines at higher tem- 
peratures lie wholly within the triangle and approach each other 
as the temperature rises, disappearing finally at about 92° in the 
point F. The composition at the point F is approximately 59 °/, of 
water, 12°/, of acetone and 29 %, of phenol. 
Above 92° the ¢-surface is convex at every point when regarded 
from below; as the temperature falls a double plaitpoint therefore 
appears at the point F, when this temperature of 92° is reached. 
On further depression of the temperature the point F develops into 
a plait with two plaitpoints, of which one moves towards the side 
W. Ph. where it disappears at 68° in the point at which the con- 
nodal line of 68° touches the side W. Ph.; at still lower tempera- 
tures therefore one point of folding alone remains. 
A further investigation will show whether it is possible in some 
measure te learn the course of the plaitpointcurve. 
Mr. ScHREINEMAKERS has thus shown experimentally that connodal 
lines with two, one or no plaitpoints may appear on the ¢-surface. 
The first example with two plaitpoints has been communicated in 
the preceding paper; in previous investigations connodal lines with 
one and with no plaitpoint were referred to. 
Chemistry. — “On the nitration of benzoic acid and its methylic 
and ethylic salts.’ By Prof. A. F. HOLLEMAN. (Communi- 
cated by Prof. C. A. LoBpry DE BRUYN.) 
Some time ago (Recueil 17.335) I described a process for the 
quantitative determination of the three isomeric mononitrobenzoie 
acids in mixtures of them. ‘This process has been simplified and 
improved so that the results obtained by it now attain an accuracy 
