
DIMETHYL-THETINE AND ITS DERIVATIVES. 573 
or as— 
CH, 
oH,—$—cH,—co 
Ne: 
cb_cn,_d_on, 
CH, 
exactly as similar alternative formule have been proposed for free betaine. 

Hydrobromate of Dimethyl-Thetine.—This substance, from which all the 
derivatives of dimethyl-thetine are obtained, is produced by the action of 
sulphide of methyl on bromacetic acid at ordinary temperatures. 
For its preparation, sulphide of methyl and bromacetic acid are mixed in a 
flask connected with a vertical condenser. The flask with condenser attached 
is then placed in a tub of water, and so arranged that from time to time it may 
be removed and agitated. Conveniently the tub of water is placed in the 
corner of a room and the condenser supported by leaning against the angle. 
The bromacetic acid rapidly dissolves, but to ensure complete solution the 
flask should be well shaken, otherwise the thetine compound begins to separate 
out before the whole of the acid dissolves. 
The bromacetic acid is so soluble in sulphide of methyl that the temperature 
of the mixture sinks below zero, and in one experiment a minimum of — 5° C. 
was observed. 
As soon as the whole of the bromacetic acid has dissolved, the mixture 
begins to grow cloudy, and almost immediately yellowish oily drops begin to 
separate out; these rapidly increase in quantity, and soon unite to a layer, 
which eventually forms the greater part of the product. As the oily liquid 
increases in quantity the temperature of the mixture rises; the action, indeed, 
is so energetic that unless it be checked by cooling the flask in water, the 
sulphide of methyl boils off with such violence that even with a long condenser 
the greater part may be lost. On the termination of the action (which 
occurs in an hour or two) the product consists of two distinct layers. The 
lower of these is almost pure dimethyl-thetine hydrobromate ; the upper a 
solution of the thetine compound in sulphide of methyl. The condenser is 
now removed, the flask loosely corked * and left to itself for a night. Next 
| day the lower oily layer is found to have completely solidified, whilst the upper 
pala tightly corked, the flask, unless strong, may burst inwards owing to the absorption which occurs. 
