184 
it is possible to determine by the electro-optic method a transition 
temperature of the two modifications of the sal-ammoniac fogs, which 
we have discovered. Other examples will be tried also. 
(To be continued). 
Chemistry. — “On critical end-points in ternary systems. Il. By 
Prof. A. Smits. (Communicated by Prof. A. F. HorLEMAN). 
In two previous communications I already discussed some parti- 
cularities which may occur in ternary systems obtained by the 
addition to a system of the type ether-anthraquinone of a third 
substance which presents critical end-points neither with anthraquinone, 
nor with ether’). An example of this was naphtaline-ether-anthra- 
quinone, which was examined by Dr. Apa Prins’). 
Though some more cases were afterwards theoretically examined 
by me, the publication was postponed not to anticipate too much 
on the experimental investigation, which was greatly delayed by 
want of time. 
Now however just recently we have met with the very welcome 
circumstance that the petrographer-mineralogist Nieerr not only has 
seen that the phenomena which are found for the said systems, are 
of fundamental significance for petrography and particularly for the 
chemistry of the magna, but that moreover he has had the courage 
to enter upon an investigation of this territory, which is so compar- 
atively difficult to explore °). 
In virtue of this it seemed desirable to publish our results already 
now, the more so as I may cherish the hope to facilitate the experi- 
mental study of others somewhat in this way. 
Having discussed one of the possible types pretty fully in my last 
communication on this subject, a more general discussion of the 
classification of the different cases which might be distinguished for 
ternary systems with critical end-points may suffice here. 
1 Case. In the first place 1 will mention the case that critical 
end-points occur for only one of the three binary systems; this case 
was discussed by me before, and tested by an example by Dr. Apa Prins. 
If we call the components A, B, and C, and if critical end-points 
occur only in the system A—C, we know that the ternary system 
1) These Proc. 25 Sept. 1909. 182. 
2 » 24 Sept. 1910. 342. 
2) These Proc, 24 Sept. 1910. 353. 
3) Zeitschr. f. Anorg. chem. 75. (1912). 
