236 



REV. S. M. JOHNSTON 



N0 3 ion two and one half molecules of water of hydration, on the assumption that the 

 hydrogen ion does not hydrate. 



The above results are mean values of the several experiments made by Garrard 

 and Oppermann. 



The values they obtained for the several ions considered are : — 



Cl Ion. 



Br Ion. 



N0 3 Ion. 



S0 4 Ion. 



7-4 



31 



2-1 



6-5 



5-0 



5-2 



1-8 



171 



31 



4-9 



1-2 



8-8 



5-4 



5-6 



4-1 





1-6 



2-9 



2-7 





2-0 



3-2 



3-0 





Treating the results I have obtained for the ammonia salts as the above experi- 

 menters did theirs, that is, assuming that the NH 4 ion does not hydrate. As the ionic 

 hydrations I have given above are mean values for the two ions, these must be doubled 

 for monovalent and trebled if one be bivalent, under the above assumption, i.e. that the 

 NH 4 ion does not hydrate. 



The following are the results : — 



Cl Ion. 



Br Ion. 



N0 3 Ion. 



S0 4 Ion. 



•10 



2-8 



1-2 



6-6 



1-84 



3-0 



2-0 



6-9 



2-2 



3-6 



2-0 



6-9 



3-0 



4-2 



2-0 



6-0 



3-4 



4-2 



1-0 



•4 



7-5 



3-8 



4-6 





7-2 



4-0 



4-4 





75 



4-0 



4-8 





6-9 



3-0 



4-6 





5-4 



2-6 



4-4 





4-8 





4-4 





4-8 





4-0 







The above figures show an agreement in hydration values which is scarcely less 

 than striking when it is remembered they have been obtained by two wholly different 

 methods. 



Had Garrard and Oppermann given the concentration or concentrations at which 

 they worked, it would have been possible to make the comparison more complete. 



For concentrations over a wide range, the hydration values I have obtained are 

 nearly constant. 



II 'JARRAKDand Oppermann worked at a constant concentration, then my results 

 would be in striking contrast to theirs, as for a considerable range of concentration I 



