406 ME. ^Y. IIOPKIXS OX THE COXSTEUCTIOX OF A XEM" CALOEBEETEB 
Mean value of A=2'110 ; and therefore 
Q'>=2-ll0a%a*-l) + -00Us(^:^y'f~^ (14.) 
21. It only remains to detennine the capacity for heat of the calorimeter, and so to 
modify the numerical values of the coefficients in the preceding formulae as to obtain 
numerical values of Q in which unity shall represent the quantity of heat required to 
raise a given weight of distilled water one degree Centigrade. I shall assume this given 
weight to be 1000 grains. 
In the first place it was necessary to determine the weight of the distilled water used 
in the experiments, and that of the tin vessel containing it. For this purpose the vessel 
was filled with water while the bulb of its thermometer was stiU inserted in it. Tire 
thermometer was then removed, and the vessel and contained water was found to weigh 
8524 grs. 
Wheir empty and dry, the vessel itself weighed 
3170-5 grs., 
and consequently the weight of water was 
5353-5 grs. 
The tin plate of which the vessel was formed consisted of thin sheet iron coated with 
tin, the weight of which was of that of the iron. Also the capacity for heat of 
sheet iron may be taken =*11, and that of tin =-06, the capacify of water being 
unity. Let and be the weights of iron and tin respectively in the tin plate, and c 
its capacity for heat. Then if W= the weight of the vessel, 
w. . 
— to * 
also 
ty,= ^ W, and ^ 2 = — "W, 
and the weight of water equivalent to Wj of iron and iv.^ of tin, 
=w,(- 11 )+W 2 (- 06 ) 
=W(-l + -0055) 
= 319 grs. 
Anotlier small correction is required for the bulb of the thermometer and the small 
portion of the glass tube inserted within the vessel of the calorimeter, and the merciu-y 
contained in the thermometer. The v olumes of the glass and mercury were carefully 
estimated, and thence their weights ascertained. It was then easy to estimate approxi- 
mately their capacity for heat, which was found to be equal to that of about IT grains 
of water. This, being added to tlie correction of the last paragraph, gives 336 grains as 
the equivalent quantity of water to be added to the 5353-5 grains contained in the 
