418 
(1.)* C 4 H 5 I + 2 Cl = C 4 H 5 C1 + I Cl 
(2.) C 4 H 5 I + 2 Zn = C 4 H 5 Zn + Zn I, 
we must be prepared to anticipate the analogous recomposition — 
(3.) C 4 H 5 I + S 2 C1 = C 4 H 5 C1 + S 2 I. 
This the more, since in the case of certain compound groups, such 
as Na Sn, we find 
(4.) C 4 H 5 I + NaSn = C 4 H 5 Sn + NaI. 
The method I employ for the preparation of the bisulphide of 
iodine is, in fact, based upon the validity of equation (3). Recom- 
positions quite akin to (3) are undergone by the iodides of methyl 
and of amyl, whence we may assert the general equation (5) — 
(5.) C„H n+1 1 + S 2 Cl±= C n H„q. 1 Cl + S 2 I. 
For obvious reasons, the ethyl compound is preferred. 
The reciprocal action of iodide of ethyl and bisulphide of chlo- 
rine is perhaps as interesting in its manner as in its result. The 
two liquids may be mixed in all proportions without a greater 
change in colour than is due to the dilution of the coloured sulphide 
by the colourless iodide ; neither is heat liberated, nor other imme- 
diate token given of chemical change taking place. The change 
appears to be complete in about twelve hours. If the recomposition 
vessel be open to the air, the chloride of ethyl evaporates as it is 
formed, leaving the bisulphide of iodine in magnificent crystals, 
contaminated, however, by the products of the action of the mois- 
ture of the air upon the bisulphide of chlorine. For this reason 
the process is best conducted in a hermetically sealed tube. The 
co-reagents are used in the proportion shown by the equation, a 
very slight excess of the iodide being added. 
On opening a tube so charged which has been left overnight, and 
applying the heat of the hand, the chloride of ethyl escapes. A 
gentle heat suffices to expel the residual iodide of ethyl, whereupon 
the bisulphide of iodine is left in the form of fine tabular crystals, 
of the lustre of iodine and in a state of absolute purity. 
Although the exact composition of the substance may be fairly 
deduced from its synthesis, it was submitted to analysis in the fol- 
lowing way: — 0*3270 grins, were heated in a combustion-tube with 
nitrate of potash and carbonate of soda, whereupon the iodine and 
* Equation (1) expresses only the initial recomposition between chlorine 
and iodide of ethyl. The ultimate products are I Cl 3 , along with hydrochloric 
acid and chlorine substitution products of C 4 H 5 C1. 
