722 Proceedings of Royal Society of Edinburgh. [sess. 
The Constitution of Complex Salts. — I. Derivatives of 
the Sesquioxides. By Alexander T. Cameron, M.A. 
Communicated by Dr Hugh Marshall, F.R.S. 
(MS. received February 20, 1905. head same date.) 
Preliminary. 
In a recent communication * I described how I had obtained 
crystals of potassium hydrogen succinate showing only curved 
faces, from an attempt, up to the present unsuccessful, to prepare 
complex derivatives of succinic acid corresponding to the chrom- 
oxalates. In searching the voluminous literature of the subject 
for particulars of such complex salts I especially noticed two 
things, — first, the frequent but hitherto scarcely noted parallelism 
exhibited by these compounds ; and second, the noticeable lack of 
uniformity in the formulae attributed to them. 
The former I shall deal with in the general part of this paper, 
the latter in this preliminary portion. 
The complex sulphates and oxalates are typical examples of 
these salts, and may therefore be selected for consideration. 
Graham and Mitscherlich ascribed to Gregory’s blue chromoxalate 
the “ double-salt” formula 
3K 2 0.C 2 0 3 + Cr 2 0 3 .3C 2 0 3 + 6H 2 0 , 
while Crofts f ascribed to the red salt which he discovered a 
similar formula 
K 2 0.C 2 0 3 + Cr 2 0 3 .3C 2 0 3 + 12H 2 0 . J 
Malaguti § considered that these and similar compounds should be 
regarded as complex derivatives of chromic oxide ; and E. A. 
Werner, for reasons which I shall mention immediately, considered 
that K 6 Cr 2 (C 2 0 4 ) 6 , 6H 2 0 , and not the empirical formula, correctly 
* Proc. Roy. Soc. Edin., 25, p. 401. 
t Phil. Mag., iii., 21, p. 197. 
+ These formulae are here written in accordance with modern atomic 
weights. 
§ Compt. Rend., 16, p. 456. 
