372 Gooch and McClenahan — Typical Hydrous Chlorides. 



air loses water appreciably at 101°, the loss in an atmosphere 

 of. hydrogen chloride is not considerable until the temperature 

 rises to abont 130.° In both cases, however, loss of weight 

 is accompanied by hydrolytic action. At the outset, for 

 every gram-molecule of water liberated approximately a gram- 

 molecule of hydrogen chloride is eliminated : later the propor- 

 tion of water to the hydrogen chloride increases, because, no 

 doubt, the aluminum hydroxide hrst formed begins to lose 

 water. 



Discussion of Results. 



It appears that hydrogen chloride is without influence of any 

 kind in the dehydration of hydrous barium chloride, BaCl 2 ' 

 2H 2 0, at temperatures not exceeding 100°, at which the process 

 is complete. 



In dehydrating hydrous magnesium chloride, MgCl 2 , 6H 2 0, 

 hydrogen chloride appears to have little or no effect upon the 

 loss of the first third of the water (which may be removed at 

 100°), to act in restraint of the process of dehydration when 

 the salt is placed at once in an atmosphere heated to a point 

 between 100° and 130°, and to aid dehydration at temperatures 

 above 130°. The hydrolytic dissociation of the salt is not very 

 marked in either air or hydrogen chloride until the temperature 

 approaches 200°. 



The dehydration of aluminum chloride, A1C1 3 '6H 2 0, is inhib- 

 ited by an atmosphere of hydrogen chloride until a temperature 

 of about 130° is reached. Above that point, as in air above 

 100°, water and hydrogen chloride are evolved simultaneously. 



In attempting to account for the relation of water of crys- 

 tallization to the general molecular configuration of hydrous 



