1898-99.] Dr Marshall on Hydrolysis of Thcdlic Sulphate. 597 
though probably in these cases also the amount of hydrolysis 
would be diminished. 
The brown precipitate produced by the action of water on the 
thallic salts is stated to be thallic hydrate, not a basic salt. In 
that case the action might be supposed to be that expressed by 
the equation 
T1 2 (S0 4 ) 3 + 6H 2 0 = 2T1(0H) 3 + 3H 2 S0 4 . 
According to Lamy, however, thallic hydrate is a metahydrate 
(TIO.OH), though Strecker states that he could obtain only the 
anhydrous oxide. This might be explained by assuming that the 
orthohydrate [Tl(OH)J is first produced, but loses water sub- 
sequently. There is, however, another difficulty. Willm states 
that he experienced great difficulty in preparing normal 
thallic sulphate, but readily obtained a colourless basic salt, 
T1 2 0(S0 4 ) 2 5H 2 0, by crystallisation from strongly acid solutions; 
a similar but less hydrated salt was even precipitated by the 
addition of concentrated sulphuric acid to the solution. Strecker 
prepared and analysed the normal salt, to which he ascribes the 
formula T1 2 (S0 4 ) 3 7H 2 0, but says nothing about a simple basic salt. 
By addition of solution of potassium hydrogen sulphate to his 
thallic sulphate solution, on the other hand, he obtained a white 
crystalline precipitate, having the composition expressed by the 
formula T1 2 0(S0 4 ) 2 2K 2 S0 4 . 
There is therefore some doubt as to whether normal thallic 
sulphate exists in the ordinary solution containing dilute acid. 
As it would be of considerable interest to have the matter cleared 
up, I have commenced an investigation of the thallic sulphates 
and their double salts, and I also propose to investigate 
quantitatively the action of water upon them. 
If it is desired simply to show the action of heat on thallic 
sulphate solution, without requiring specially to prepare the pure 
salt, this may be effected by warming thallous sulphate and 
ammonium persulphate with a little water. If the ammonium per- 
sulphate is approximately pure, equal weights of the two salts may 
be taken. A considerable amount of brown precipitate separates ; 
the mixture should then be allowed to cool, and filtered, or sulphuric 
acid may be added till the precipitate is just dissolved. The clear 
solution, obtained in either way, gives a precipitate on heating. 
