Prof. Draper's Descripti he Tithonometer. 227 
held in solution; perhaps:a 
through such a solniial hye r0 
obtain that degree of saturation by vol- 
ow long the electrolysis is continued, if 
allowed to pass through the liquid. 
liged to decompose commercial muriatic acid in a alae 
vessel. Phe positive electrodes being at the bottom of the vessel, 
ind the negative at the surface of the liquid. Under these cir- 
cumstances, the chlorine as it is disengaged is rapidly taken up, 
and the hydrogen being set free without its bubbles passing 
through the mass, the impregnation is carried to the point re- 
quired. 
Although this chlorinated muriatic acid cannot of course be 
kept in contact with the platina wires without acting on them, 
the action is much slower than might have been anticipated. I 
have examined the wires of tithonometers that had been in ac- 
tive use for four months, and could not perceive the platina sen- 
sibly destroyed. It is well however to put a piece of platina foil 
in the bottle in which the supply of chlorinated muriatie acid is 
kept ; it communicates to it slowly the proper golden tint. 
The liquid, being impregnated with chlorine in this manner 
until it exhales the odor of that gas, is to be transferred to the 
siphon adc of the tithonometer, and its constitution finally ad- 
justed as hereafter shown. 
Thirdly, of the Voltaic Battery—The battery, which will be 
found most applicable’for these purposes, consists of two Grove’s 
cells, the zinc surrounding the platina. 
The following are the dimensions of the pairs which I use. 
The platina plate is half an inch wide and two inches long; it 
dips inte a cylinder of porous biscuit-ware of the same dimen- 
sions, which contains nitric acid. Outside this porous vessel is 
the zinc, which is a cylinder one inch diameter, two inches long, 
and two tenths thick; it is amalgamated. The whole is con- 
tained in a cup two inches in —— and two deep, which also 
receives the dilute sulphuric aci 
