On the Method of Condensation in Calorimetry. 357 



(2.) The piece of zinc was counterpoised in air, but the density of 

 steam being less than that of air there was an apparent increase of 

 weight on the replacement of the air by steam, to an amount equiva- 

 lent to the volume of the substance multiplied by the specific gravity 

 of steam (air being unity) at the pressure prevailing. It is sufficient 

 to take this generally as equal to 0*00062 gram per cubic centimetre 

 displacement (see Appendix). Taking the specific gravity of zinc as 

 7, and its weight being 48*300 grams, the value of the correction is — 



x 0-00062=0-0043 gram. 



The total deduction from the weight of condensation observed is 

 then 0'0358 ; we take this as 0*036 in view of the limits of accuracy 

 imposed by the balance. This leaves, as very nearly the true con- 

 densation due to the calorific capacity of the piece of zinc raised from 

 $i to t 2 , the weight 0*762 gram. The quantities are now collected — 



W= 48-300 

 w = 0-762 

 t x = 10-73° 

 t 2 =100-25° 



\ = 536*4, at this temperature (see Ap- 

 Then by the formula previously given 



pendix) . 



Specific heat of zinc 



0-762x536-4 



(100*25- 

 = 0*09453. 



10-73) x 48*3 



Degree of Accuracy attained by the Method. 



In a similar way the quantities recorded in the following tables of 

 experiments on metallic elements have been obtained. 



Table of Experiments on some Metallic Elements. 



Zinc. — Cast and cooled slowly. Free from arsenic, and probably 



nearly pure. 



w. 





h. 



w. 



Sp. h. 



Other observers. 



48 -300 .... 



15 



70 



99-76 



0-714 



-09434 





„ .... 



15 



74 



99-80 



0-73 3 



09421 



10° to 100° 



. . . . 



15 



86 



99-80 



0-713 



-09434 



Bunsen 0*0935 



.... 



10 



73 



100 25 



0-762 



-09453 



Regnault 0-09555 



,, .... 



13 



80 



100 -20 



0-7345 



09443 

















Dulong and Petit 093 



Mean .... 



14° 





100° 





-09437 





