376 Gooch and McClenahan — Typical Hydrous Chlorides. 



indicates the experimental fact that water cannot be removed 

 from the salt without simultaneous breaking out of hydrogen 

 chloride at least in the primary action, and suggests that 

 increase in the concentration of hydrogen chloride in the sys- 

 tem should retard the dehydration of the salt, as was observed. 

 The symbol 



H H 



Mg 



\ 



1 

 ^o - 



i 

 -O- 



-ci = o/' 



/ 1 



i 



H 



H 



H 



H 



H 



-Cl=OC 



\A- 



i 

 - - 



I 



i 



\ 



H 



H 



H 



shows that one-third of the water in the salt should be evolved 

 easily and without hydrolytic effect. Thereafter, the atmos- 

 phere of hydrogen chloride will act to increase the stability of 

 the chloride now containing four molecules of water within 

 the complex and so to limit the rate of dehydration as compared 

 with that in air for some range of temperature, as was observed 

 between 100° and 130°. The limit of increased stability once 

 passed, the rate of dehydration will depend upon the predom- 

 inance of the primary effect of decomposition w ; ith liberation 

 of water and hydrogen chloride or of the secondary action 

 of hydrogen chloride upon the residual oxide or hydroxide. 

 In case*the secondary effect predominates, the rate of dehydra- 

 tion will be greater in the atmosphere of hydrogen chloride, as 

 it was in six out of seven experiments at temperatures between 

 120 and 215°. 



So it appears, that the phenomena of dehydration of the 

 hydrous chlorides under discussion, in the atmosphere of hydro- 

 gen chloride as well as when heated per se, find reasonable 

 expression upon the hypothesis of varying relations of position 

 of the water within the molecular complex, as suggested by 

 Cushman upon the assumption of quadrivalent oxygen. The 

 behaviour of hydrous chlorides in an atmosphere of hydrogen 

 chloride should in many cases afford means of differentiating 

 the water within the complex from water attached externally. 



