and the Sulphurets of Kakodyl. 185 
stalline mass. When heated more strongly it is decomposed, 
like many inorganic sulphurets, into free sulphur and proto- 
sulphuret of kakodyle, which is driven off. This compound is 
easily soluble in alcohol and ether, but perfectly insoluble in 
water; concentrated nitric acid oxidizes it with great violence; 
fuming acid even causes combustion and explosion. It may be 
reduced with the same ease with which it is formed. Mercury 
effects itin the cold; the products are sulphuret of mercury 
and protosulphuret of kakodyle. The products of this action 
will of course be different at different temperatures, for I have 
already shown that the protosulphuret is decomposed at a 
temperature of 200° C. 
Persulphuret or Tersulphuret of Kakodyle. 
I have not succeeded in obtaining this substance in an iso- 
lated state, but the action of sulphuretted hydrogen on kako- 
dylic acid and its salts renders the existence of a sulphuret 
analogous to kakodylic acid almost a matter of certainty; this 
action of sulphuretted hydrogen is extremely remarkable. 
When dry sulphuretted hydrogen is passed over anhydrous 
kakodylic acid, even at ordinary temperatures, such an intense 
heat is produced that the vessel containing the acid must be 
well cooled in order to prevent a complete decomposition of 
the products: these are protosulphuret and bisulphuret of 
kakodyl and free sulphur. The same decomposition ensues 
when sulphuretted hydrogen is passed through an alcoholic 
solution of kakodylic acid. This action is perfectly similar 
to that of sulphuretted hydrogen on several metallic acids. 
If however sulphuretted hydrogen be passed into a solution 
of kakodylate of potassa, there is no more precipitate than in 
the cases of the salts of metallic acids: this is only produced 
on the addition of a stronger acid, and is the same as that 
produced from kakodylic acid. 
If however acetic acid be added to the solution until a feeble 
acid reaction is observable, no precipitation is produced. So- 
lutions of metallic salts produce in this mixture precipitates 
similar to the kakodylates, in which the tersulphuret of ka- 
kodyle plays the part of the acid, and the metallic sulphuret 
that of the base. 
I must for the present content myself with simply noticing 
the existence of these curious sulphur salts, at a future period 
I shall publish a fuller examination of them. 
The results of the above research prove most satisfactorily 
the great similarity which exists between kakodyle and certain 
metals. 
