On the Heat evolved in Chemical Combination. 1 9 



retted waters. But if paramount duty should oppose itself to 

 such a course, we have a certain remedy to propose. You 

 have seen how instantly chlorine destroys the gas. Chlorine 

 and sulphuretted hydrogen cannot coexist together. Plentiful 

 fumigations of chlorine would therefore infallibly prevent the 

 deleterious effects ; and the antidote is at once cheap, and in- 

 capable, under proper management, of producing any injuri- 

 ous effects to counterbalance its advantages. 



The Lords of the Admiralty have received these sugges- 

 tions with indulgence, and have given instructions to their 

 cruisers upon the African coast to test the waters at regular 

 intervals. They have also abundantly supplied the African 

 expedition with the means of chlorine fumigation ; and I have 

 the gratification of knowing that the views which I have now 

 had the honour of submitting to you, have tended to give con- 

 fidence not only to the gallant band who have devoted them- 

 selves to one of the most disinterested enterprises which ever 

 emanated from pure Christian charity, but to the numerous 

 friends who wait the result with anxiety. 



II. Abstract of recent Researches on the quantity of Heat 

 evolved in Chemical Combination, particularly those of MM. 

 Dulong and Hess. 



"C^ARADAY having established the law of definite electro- 

 ■"• lytic action, and thus connected together the two princi- 

 ples under which scientific chemistry at the present day is 

 organized, the abstract and the numerical, the electro-chemical 

 theory and the law of equivalents, it became an interesting 

 point to examine whether affinity possessed the same definite- 

 ness of character in relation to other physical agents, and 

 especially to heat, the influence of which on affinity is even 

 more remarkable than that of electricity, and with whose 

 operations indeed chemistry itself, until a comparatively recent 

 date, was identified. 



Investigations tending to this end had been long since 

 entered on. The measurement of the quantity of heat evolved 

 in combustion was, independent of all relations to scientific 

 theory, a problem of such technical importance, that it has 

 occupied from time to time all those philosophers who de- 

 voted themselves to that branch of science. Their results, 

 frequently discordant, but still often useful, have been con- 

 sidered, especially those of Despretz, as indicating that the 

 heat evolved was proportional to the quantity of oxygen which 

 entered into combination. 



For some time before his death, M. Dulong had been occu- 



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