﻿and Expansions of some Liquids. 143 



n. 



Calculated. 



Thomsen 



4 



.... 



92-7 



9 



182-2 



182-0 



19 



361-2 



360-8 



49 



896-2 



899-6 



99 



1794 



1795 



99 



3592 



3591 



The agreement is as satisfactory as could be expected. 



I feared that the method employed in these determinations, 

 very suitable for saline solutions or for mixtures of acid with 

 water in excess, would involve much uncertainty in the case of 

 sulphuric acid monohydrated or mixed with a very small pro- 

 portion of water. 



Indeed, such a liquid tending, instead of evaporating in con- 

 tact with the air, to absorb humidity from it and become heated, 

 the experiments are no longer made in identical conditions with 

 those of the experiments for comparison on water ; so that, to 

 obtain a temperature stationary at the beginning of an experi- 

 ment, the temperature of the acid-bath must be about 4° above 

 the atmospheric. Besides, the great difference in specific heat 

 of the liquids obliges us to use very different volumes of them. 



This fear induced me to repeat the determinations for the mo- 

 nohydrated acid, alone and with from one to five equivalents of 

 water, by the second method — the one I used for the solutions 

 in sulphide of carbon. 



But then another difficulty is encountered. Either on account 

 of the viscosity of the concentrated acid, or because the greater 

 volume we are obliged to put in the balloon in order to have a 

 calorific mass equal to that of the water prevents the different 

 parts from being so well mixed by the agitation, the transmis- 

 sion of the heat to the water of the calorimeter takes place more 

 slowly. Now, if the experiment lasts longer, the losses by ra- 

 diation are no longer identical. This inconvenience can be 

 remedied, after some trials, by so regulating the velocity of the 

 agitation of the balloon in the calorimeter that each of the ex- 

 periments shall occupy the same time. 



This second series of experiments gave the following results, 

 expressing the specific heat between 20° and 56° : — 



n. c. p. C. C — 18rc. 







03363 



98 



33 





1 



0-4411 



116 



51-2 



33-2 



3 



0-5056 



152 



76-8 



22-8 



5 



0-5833 



188 



109-7 



19-7 



Let us now compare these results with those of the preceding 

 experiments or obtained by other observers. 



