534 



ally, the sides of (lie quadrangle have been omitted, only a part 

 of the diagonals with their jtoint of intersection W is drawn. Fig. 1 

 is not the representation in space of the equilibria, but their pro- 

 jection on the quadrangle. Before discussing the quaternary equili- 

 brium, we will first consider the four ternary equilibria. 



2. llie ternary equilibria. 



a. The system K^SO^ — KCl — H^ 0. 



Only K2SO4 and KCl occur as solid phases; in fig. 1 the satura- 

 tioncurve of KaSO^ is rej)resented by hy and that of KCl by fg. 

 Consequently point h represents the solubility of K^SO^, point ƒ the 

 «olubility of KCl in water; point y is the solution, saturated with 

 the two salts. 



b. The system CuSO, — A\SO, — H,0. 



This system was examined already formerly ^) ; as solid phases 

 occur K,SO„ CuSO, . 5H.,0 and the doublesalt CuSO, . K,SO, . 6H,0. 

 The isotherms of 30° and 40° are determined experimentally ; that 

 of 30° is represented schematically in the figure. The saturation- 

 curve of K2SO4 has been represented by hi, that of CuSO^ . ÖH^O 

 by ak and that of tlie doublesalt by Id. When we represent this 

 doublesalt in fig. i by the point Di.^.g (hen the line WD^.j-g intersects 

 the curve ik in a point y. The doublesalt is, therefore, soluble in 

 water without decomposition; its solution saturated at 30° is repre- 

 sented by r. 



The following is still of importance for the investigation of 

 the quaternary system. When we heat an aqueous solution of 

 K3SO4 -|- CuSO^ above 50°, a light green salt is separated from the 

 solution. Meerburg found for the composition of this salt: 



4Cu() . K,0 . 4SO3 • '^^,0, 

 while Brunner "), who examined first this basical salt has found 

 four molecules instead of 3 molecules H^O. 



c. The system CuSO^ — CuCl^ — ti-^O- 



Also this system was investigated formerly =*). as solid sub- 

 stances occur: CUSO4.5H2O and CuCl^ . SH^O. In fig. 1 a/j represents 

 the saturationcurve of CuSO^ . SHjO and cb that of CUCI2 . 2H2O. 



d. The system Cu CI, — KCl — H, 0. 



In this system of 'which the invariant (P) equilibria were 



1) P. A. Meerbukg. Gedenkboek J. M. van Bemmelen, 356 (1910). 



2) Beunner. Pogg. Ann. 15 476 (1829). 



3) F. A. H. ScHREiNEMAKERS. Tlicse Communications I.e. and Zeilschr. Phys. Chera. 

 69 557 (1809). 



