590 DRE. A. LETTS ON THE COMPOUNDS OF ETHYL-, ETC., THETINES. 
In concluding this paper it may not be superfluous to make a few remarks — 
on the thetines as a class. 
A sulphide of the series (C,H2,,1).5 , when treated in the cold with brom- 
acetic acid, combines with it to form the hydrobromate of a thetine— 
C Hon41;5 ipuoutd 
S + Br—CH,—COOH = Br—S—CH,—COOH. 
| : 
Cp Hon+1 Cn Hon41 
The intensity of the reaction and the quantity of hydrocarbon sulphide 
combining with the bromacetic acid decrease as the series is ascended. In 
the case of the first member of the series—sulphide of methyl—nearly the 
whole of it combines with the bromacetic acid, and the action is so energeti¢ 
that unless checked by cooling, the sulphide of methyl boils off; whereas in 
the case of sulphide of amyl the mixture has to be warmed before a reaction 
occurs, and even then less than half the sulphide enters into combination. 
The production of a thetine hydrobromate is almost invariably attended with 
the following phenomena :—The bromacetic acid dissolves in the sulphide with 
fall of temperature—the solubility of the acid and therefore the extent of this 
fall decreasing as the series of sulphides is ascended. An oily liquid gradually 
‘separates from the solution as soon as the bromacetic acid is dissolved, and. 
this liquid consists for the greater part of the thetine hydrobromate. The latter 
is more or less soluble in excess of the hydrocarbon sulphide. The separation 
of oily liquid appears to be characteristic of the formation of a thetine hydro- 
bromate. 
Considerable differences are observed in the properties of the thetine 
compounds. All the derivatives of dimethyl-thetine crystallise with remarkable 
ease. In the ethyl series only the hydrobromate, lead salt, and chloro-platinate 
have been obtained crystallised ; and in the higher series only the lead salts 
(which are perhaps not of definite composition) are crystalline. 
The action of heat on the thetine compounds is described in a separate 
paper, p. 591, as also the action of hydrocarbon sulphides on bromacetic acid, 
p. 612. It appears probable that only sulphides of the series (C,H»,1,).8 are 
capable of combining with bromacetic acid, and that in other series the action 
is similar to that which occurs when a sulphide of the (C,H,,,,),S series is 
heated with bromacetic acid. 
The action of oxidising agents on the compounds of dimethyl-thetine, p. 601, 
shows that in the latter the hydrocarbon sulphide retains to a certain extent its | 
original properties. | 

