( fi« ) 



and C for the violet clu'oiuic cliloride. Botli are taken in the 

 caleiihition as hydrates with 6 H^O so that the sum of H^O and the 

 two lijdrates is always taken as 100 (percentage by weight). 



The line AGH first runs close to the axis AC. This means that 

 in weak solutions a final condition is reached in which the chromic 

 chloride occurs nearly exclusively in the violet modification. 



Strictly speaking this means in the condition in which the violet 

 chromic chloride finds itself the moment it has dissolved. Briefly, 

 we will call this the violet condition. If, therefore, we make a 

 solution of the green chloride of the same concentration the green 

 chloride will be almost completely changed into the violet salt. This 

 process proceeds slowly enough to admit of its course being studied, 

 also to show that both green and violet lead to the same final condition. 



If the amount of hydrated chromic chloride exceeds 20 "/„ the line 

 A I G begins to run perceptibly upwards and consequentl}" the final 

 condition in the solution shifts more and more towards green. 



In the point I the final equilibrium is situated near an equal 

 amount of green and violet. This corresponds with a total of 65 7o of 

 chloride ') of which 32.5 "/„ is green and 32.5 "/„ violet. 



It will be noticed that we cannot go further than G because the 

 solution there reaches its saturation. If crystallisation did not take 

 place the prolongation of the line AI G could be determined. If 

 this may be represented by G H, the terminal point H would 

 indicate the amount of green and of violet chloride in liquid hydrate 

 of chromic chloride (without excess of water); this point would 

 therefore lie at about 157„ violet and 857„ green. Its determination 

 is however impossible as the green hydrate melts at 83° and the 

 violet one at 92°. Although the melted hydrates crystallise very 

 slowly still it is difficult to keep them liquid down to 25°. 



The final condition of solutions of different concentrations thus 

 being known, the solubility of the two-hydi-ates at 25^ was studied. 

 The saturation was very soon accomplished, 1) and E represent 

 the concentrations of freshly prepared saturated solutions of green 

 and violet chloride. 



These, however, soon undergo a modification. In the green solution 

 violet chloride is formed and conversely. This causes a change in 

 the solubility which runs along the lines BF and EF respectively. 

 These show that the total solubility of both green and violet increases 

 as the transformation of green into violet or the reverse proceeds in 

 the solution. 



1) This total amotiiit may be read off on AC or AB if we draw from I a Hue 

 parallel with BC- 



