1901-2.] Dissociation of Compound of Iodine and Thio-urea. 233 
The Dissociation of the Compound of Iodine and 
Thio-urea. By Hugh Marshall, D.Sc. 
(Read June 2, 1902.) 
When thio-urea is treated with suitable oxidising agents in 
presence of acids, salts are formed corresponding to the general 
formula (CSN 2 H 4 ) 2 X 2 
2CSX 2 H 4 + 2HX + 0 === (CSN 2 H 4 ) 2 X 2 + H 2 0 . 
Of these salts the di-nitrate is very sparingly soluble, and is pre- 
cipitated on the addition of nitric acid or a nitrate to solutions of 
the other salts. The salts, as a class, are not very stable, and their 
solutions decompose, especially on warming, with formation of 
sulphur, thio-urea, cyanamide, and free acid. A corresponding 
decomposition results immediately on the addition of alkali, and 
this constitutes a very characteristic reaction for these salts. 
The di-chloride and di-bromide were prepared by Claus * by the 
direct action of the corresponding halogen on an alcoholic solution 
of thio-urea ; he found, however, that under similar conditions the 
di-iodide was not produced. 
McGowan f investigated a number of the salts and prepared 
them in various ways. Among other experiments, he tried the 
action of the chlorides of iodine on alcoholic solution of thio-urea ; 
this he found gave rise to the di-chloride of the base and free 
iodine ; he states that “ in aqueous solution the iodine separates 
more slowly.” By shaking together the di-chloride and potassium 
iodide with alcohol, there were formed potassium chloride, thio-urea, 
and free iodine; here again “in aqueous solution the separation 
of iodine proceeds more slowly.” He succeeded in preparing 
the di-iodide, however, by rubbing together solid thio-urea and 
iodine with a small quantity of alcohol, washing away excess of 
free iodine by means of benzen, and drying on filter paper. In 
* Ann. Chem. Pharm., clxxix. 139 (1875). 
t Journ. fur prakt. Chem., xxxiii. 188 (1886). 
