by the mutual reaction of Solid Substances. 211 
mixed, and in similar cases because the crystallizing point of 
these two bodies together is lower than for each alone; just as 
the freezing point “of salt water is lower than that of fresh 
water, and as the fusing point of an alloy is sometimes below 
ches of either of its constituents. 
alorimeter.—For further experiments in which the reduc- 
tion of temperature might be measured with some degree of 
accuracy, it was desirable to secure a closed —. in * which 
radiation and convection should be reduced t nimum, 
and the heat of the surroundings should be pee yee alo- 
rimeter was therefore constructed Mone oe like that used by 
Berthelot in some of his investigatio 
It consists of a coven hea ‘tank of fourteen-ounce 
tinned copper, of about twelve gallons capacity, placed in a 
much larger wooden case, the space Ss the walls of the 
tank and case being filled with loose cottor 
The upper surface of the tank has four felis each to receive 
a cylindrical vessel of polished german silver resting on cork 
supports and having av air space around and under “it. Each 
ike a pug-mi 
The thermometers have each a long stem with the scale on 
the upper part so ese readings even to as de C. can be taken 
without raising the rom the mixtu 
The tank is kept filled with see) and this is frequently 
agitated by a stirrer moved wit crank. e stirrer revolves 
horizontally i in the bottom of the. tank, and having two blades 
ike a propeller, it agitates the water thoroughly from bottom 
to top, the moistened part being always immersed. Over the 
whole is a closely-fitting wooden cover also ‘ae for the 
thermometers and stirrers. 
The salts to be mixed, after finely pulverizing, were placed 
in separate beakers within the calorimeter, and left for a time 
to acquire a uniform temperatu e ents of o 
beaker were then added to those of the other, the cover 
replaced as quickly as Pogible, the whole mixed vigor- 
ously by twirling the er. Tig action generally took 
oo were then taken, slight agitation being still continued. 
here being four beakers two experiments can be carried on 
at the same time, and as the cover is not in a single piece one 
portion can be removed without uncovering the other pair of 
beakers. 
* Water of auy desired temperature may be used, 
