728 
Proceedings of Poycd Society of Edinburgh. [sess. 
General. 
The constitution of complex salts of dibasic acids of the type 
H 2 X , and metals forming oxides of the type M 2 0 3 , may be best 
considered by taking as examples the complex chromoxalates, and 
treating them as derivatives of chromic hydroxide by the substitu- 
tion of half-saturated oxalate groups for hydroxyl radicals. 
If all the hydroxyls are replaced by the radical - C 2 0 4 K 
Gregory’s salt is obtained, to which accordingly must be given 
the constitution 
This type may be regarded as the saturated one, and will here- 
after be referred to as A. 1. 
By the elimination of potassium oxalate from two molecules of 
Gregory’s salt a compound 
is theoretically derivable. No such chromoxalate has up to the 
present been obtained, but Recoura has prepared an exactly 
analogous chromisulphate, having the constitution 
This type of salt will be referred to as A. 2. 
In type B. will be included salts which still retain one hydroxyl 
group, and in addition the compounds which can be derived from 
these by loss of water. 
The first class of type B. is obtained by substituting two - C 2 0 4 K 
radicals for hydroxyl groups in chromic hydroxide, as in the 
compound 
c 2 0 4 -k 
/A-k 
CrfCA-K 
>CA or CA = [Cr : (C 2 0 4 .K) 2 ] 2 
CAA-K 
AA-k 
S0 4 : [Cr : (S0 4 .H) 2 ] 2 . 
ca-k 
