1901-2.] Dr Hugh Marshall on Thallic Sulphates. 
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Thallic Sulphates and Double Sulphates. 
By Hugh Marshall, D.Sc. 
(Read Jane 16, 1902.) 
In a note on “ the hydrolysis of thallic sulphate ” which I com- 
municated to the Society some time ago,* I commented on the 
conflicting nature of the statements, made by various investigators, 
as to the exact composition and nature of thallic sulphate. As the 
subject appeared of some interest, I subsequently commenced an 
investigation of the salt and of the double salts derived from it. 
The results so far obtained are in some respects rather striking, 
but the investigation is not yet completed, and my reason for now 
publishing a general statement of these results is, that apparently 
others besides myself are working in the same field. A paper has 
just been published by James Locke, f in which the author describes 
a caesium thallic sulphate which he obtained while endeavouring to 
prepare caesium thallic alum. No alum could he obtained, the 
most hydrated salt corresponding to the formula CsT1(S0 4 ) 2 , 3H 2 0. 
This question of the formation of thallic alums was one to which 
I turned my attention early in the investigation. I employed 
more particularly ammonium and rubidium sulphates, and was 
quite unsuccessful, being unable to obtain even mixed alums in 
which thallium (TT”) had partly replaced other triad metals.. 
Mixed solutions prepared from ammonium chrome alum, ammonium 
sulphate, thallic sulphate, and dilute sulphuric acid were allowed 
to crystallise. Crystals of chrome alum and of a hydrated ammon- 
ium thallic sulphate formed separately ; the latter were colourless 
and of prismatic habit, and much less hydrated than an alum ; the 
chrome alum crystals were free from thallium, except a trace of 
thallous sulphate replacing ammonium sulphate. Similar results 
* Proc. R.S.E., xxii. p. 596 (1899). 
f Abstract in Chem. Central- Blatt, 1902, i. p. ] 266, from Amer. Chem ► 
Journ ., xxvii. p. 280. 
PROC. ROY. SOC. EDIN. — VOL. XXIV. 
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