Action of Heat on Compounds of Dimethyl-Thetine. 
By Dr E. A. Letts. 
(Sent for Publication August 19, 1878.) 
I was induced to study the action of heat on the compounds of dimethyl- 
thetine, from having observed that they very readily suffered change when heated 
alone, or even, indeed, in certain cases when their solutions are boiled. I 
noticed that this change is attended with the disengagement of sulphide of 
methyl in all the salts except the nitrate, and this led me to think,—bearing in 
mind the ease with which the methyl-sulphine compounds are decomposed into 
sulphide of methyl and an ether of methyl,*—that in the case of the thetine 
compounds, dissociation also occurred. Thus I believed that the hydrobromate 
of dimethyl-thetine is decomposed by heating into bromacetic acid and sulphide 
of methyl,—the substances from which it is produced by direct addition. 
In order to test the truth of this supposition, weighed quantities of the 
hydrobromate (carefuily dried over sulphuric acid till they ceased to lose 
weight) were heated on watch-glasses and in beakers in a water oven. The 
results of these experiments confirmed the fact of the decomposition of the salt, 
though at this temperature it took place very gradually, loss in weight con- 
tinuing for more than a week. 
But it soon became clear that the loss in ao which the hydrobromate 
suffered when thus heated was greater than could be accounted for on the 
assumption that simple dissociation oc- 
curred. Moreover, the residue was not 
deliquescent, and had neither the appear- 
ance nor properties of bromacetic acid. 
In order to ascertain the nature of the 
products of decomposition, a quantity of 
the hydrobromate was sealed up in a 
tube constructed according to the sketch. 
The thetine salt was placed in the limb A, 
and the limb B immersed in cold water ; 
A was then heated in oil or water. After 
five hours’ heating in a water-bath the 
hydrobromate had fused, and B contained 





a few drops of a colourless liquid. A was then heated in an oil-bath. At 
* Crum Brown and Brarkie, “ Proceedings,” vol. ix. pp. 565, 712. 
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