585 



examined formerlj ^) occur as solid phases: KCl , CiiCl^ . SH^Ó, 

 CnCI, . 2KC1 . 2H,Ó and CiiCI, . KCl. This last saU, however, occurs 

 onlj above 57°, so that at 30°: KCl, CuCl, . 2H,0 and CuCl, . 

 2KC1 . 2H5O only occur as solid phases. 



The isotherm of 30° is represented schematically in fig. 1 ; f e is 

 the saturationcurve of KCl, cd that of CuCl.^ . 2H2O and ed that of 

 CuCl, . 2KCi . 2H2O. When we represent in fig. 1 this doublesalt by 

 Dj.j.^, then the line WDj.^.g does not intersect curve cy/, but curve ƒ<?. 

 This doublesalt is, therefore, at 30° uot soluble in water without 

 decomposition, but it is decomposed with separation of KCl. 



This isotherm of 30° was determined already formerly ') ; we 

 have also still determined some points. 



3. The quaternary system. 



At first sight we may think that the examined system is built 

 up by five components; as, however, between four of these substances, 

 the reaction : 



CuCl, 4- K,SO, ^ K,C1, + CuSO, (1) 



occurs, this is not the case. 



In view of the above-mentioned double-decomposition (1) we shall 

 represent the equilibria with the aid of a quadrilateral pyramid, the 

 base of which is a quadrangle. The four anglepoints of this qua- 

 drangle indicate the four substances: CuSO^, CUCI2, K^SO^ and K2CIJ 

 and in this way that the two substances, which are in reaction (1) 

 at the same side of the reaction-sign, are united by a diagonal of 

 the quadrangle. Perpendicular above the point of intersection W of 

 the diagonals, is situated the top of tlie pyramid, which represents 

 the water. 



At the examination of this quaternary system we have always 

 remained below the temperature, at which the basical salt 



4CuO. K.,0. 4SO3. 3H2O 

 is separated. If this had not been the case, the reaction 1 

 - 4GuS0, + K,S0, + 4H,O:;t4Cu0.K,0.4S0,.3H,0 + H,SÖ,. (2) 

 would have occurred. We should then have had to examine a 

 quinary system, in which reactions (1) and (2) occur. 



As the quaternary solutions saturated with a solid substance, are 

 represented by a surface in the space, viz. the saturationsurface, we 

 have seven saturationsurfaces. We find their projections in fig. 1 ; 



1) W. Meyerhoffer. Zeilschrift fur Phys. Ghem. 336 (1889) 5 97 (1890). 

 ~) H. FiLiPPO; not yet published. 



