ACCOMPANYING BASIC SUBSTITUTIONS. 
35 
to the immersion, the heating and cooling - processes counterbalanced one another ; and 
the correction for the last 2| minutes was made on the hypothesis that the fluid 
during - that period was at the final maximum. The rate of cooling was found to 
be about 0 o, 012 per minute, for each degree of excess, the fluid being kept in constant 
agitation. 
Knowing the weight of the water, the value in terms of water of the different parts 
of the apparatus, the temperature gained by the water and lost by the instrument, 
we possess all the data necessary to calculate the thermal value of the latter in terms 
of water. 
By repeating the same experiment with an equal bulk of the liquid whose specific 
heat is required, we obtain the thermal value of the same instrument in terms of the 
liquid. From these values the specific heat may be calculated. An equal bulk of 
the liquid is employed in order to have the instrument immersed in all cases to pre- 
cisely the same depth, and, for a similar reason, it ought to be always introduced in 
a perpendicular direction into the fluid and maintained in the same position during 
the agitation. Before calculating the final result, it is necessary to obtain an ap- 
proximate one, in order to find the thermal value of the brass vessel, &c. in terms of 
the liquid. In actual practice this is easily effected without involving any sensible 
error. If the specific heat of the liquid differ considerably from that of water, the 
correction for the heating and cooling influence of the air must also be modified. 
The weights of the different parts of the apparatus and their value in water are as 
follows : — 
Mercury in bulb of thermometer by which the increment of tem- 4 
perature was measured 300 gr. X 0 - 033 J 
Glass in bulb and immersed portion of stem 24 gr. X 0 - 14 . . . 3*3 
Glass stirrer 20 gr. X0T4 2’8 
Brass vessel 420 gr. x 0 094 395 
Value of entire apparatus 55-5 
The value of the apparatus in terms of the following solutions is 57*0 grains. 
If we now make 
D. The difference between 201° and the final temperature of the liquid, or the heat 
lost by the instrument. 
e. The excess of the final temperature above the air. 
I. The increment of temperature observed. 
I c . The increment corrected. 
F. The weight of the fluid. 
Vss. The value of the apparatus in terms of the fluid. 
X. The value of the instrument in terms of fluid. 
