9/5 
therefore be represented in a triangle the apexes of which indicate : 
5, 5,Cl,, and the compound, or the new modification. 
Let us take first the case of a 
GA compound, for instance, 5,Cl,; the 
composition may then be expressed 
by a point of the triangle PQR 
in Fig. |. As unity of the com- 
es pound has been taken '/, S,CI,; 
- this has the advantage that we 
can now deduce the gross 
composition, i. e. the relation 
5:5,Cl, in a simple manner from 
P 7 a pe ras the real composition (S: S,CI, : '/, 
JC 5,Cl,), namely by projection on 
Meet the side PR. 
If O is the real composition, a mixture of this composition O 
contains PTS RUS,Cl, and UT'/, 8,C1,. The gross composition 
is now : 
cote ee UT PO 
file Sh ROL OT ROL 
Hence, O’ gives the gross composition. This is also the composition 
which one may determine experimentaliy by an estimation of the 
total sulphur. Not, however, the true composition (, for there is no 
means of determining the quantity of 5,Cl,. 
The question now arises: If we heat the mixture of varying 
sulphur content to a given temperature and then cool to a definite 
temperature, how then does the composition of the solution saturated 
after warming, vary with the original composition? This is readily 
indicated with the aid of fig. 2. 
Let the line PBHR represent the equilibrium S + $,Cl, 2 5,Cl, 
at a temperature 7’. 
Let 7 DFU represent the solubility line of 5; in mixtures of $,Cl, 
and §,Cl, at the temperature ¢,. The point 7’ then represents the 
soiubility of 5; in §,Cl,. 
When now a mixture of S and $,Cl, of the gross composition A 
is heated long enough at 7’, the equilibrium S + S, Cl, 228, Cl,, which 
belongs to the temperature 7’, sets in. The inner composition is, 
therefore, given by a point of the curve PBHR, which is found by 
drawing a line 1 PF in the gross composition of A. The intersecting 
point of this perpendicular line with PBHR gives the looked for 
real composition. If one now cools rapidly to ¢, the composition 5 
