



Mr. Hunt on Actino-Chemistry . 



I. II. %4^' 



Olefiant gas . . . . 10-19 9-25 



Carburetted hydrogen. 31-35 36-05 



Hydrogen .... 28-80 30-17 



Carbonic oxide . . 16-28 11-42 



Azote ...... 13-35 14-01 



Carbonic acid ... a trace a trace 



Atmospheric air . . 0-48 0*50 



Naphtha vapour . . a trace a trace 



Ammonia .... a trace ' 



100-35 101-40 



VII. Contributions to Actino-Chemistry. By Robert Hunt, 

 Esq., Secretary to the Royal Cornisoall Polytechnic Society, 

 Sfc.^ 



MANY of the changes produced upon photographic pre- 

 parations, by the influence of the solar rays, are of a 

 remarkable character, and few of them in the present state of 

 our knowledge can be satisfactorily explained. In some in- 

 stances it would appear that new properties are imparted to 

 bodies by exposure to sunshine ; in others, that radiation has 

 the power of disturbing the known chemical forces, and appa- 

 rently establishing a new order of affinities ; whilst in all we 

 are forced to recognise the operations of a principle, the na- 

 ture of which is involved in the most perplexing uncertainty. 

 In the hope of being enabled to follow out some of these phae- 

 nomena, under circumstances more favourable for investiga- 

 tion than those which offer themselves in the ordinary method 

 of pursuing photographic experiments with the chemical com- 

 pounds spread upon paper, where we have organic matter in- 

 terfering with the results, I have been led to examine with 

 attention the changes which take place under more simple 

 conditions. It must be evident that a subject so extensive as 

 this new branch of inquiry, embracing all material elements 

 and their combinations, will not readily admit of satisfactory 

 generalization ; in this paper, indeed, I am scarcely able to 

 do more than record a few facts, under particular heads, with- 

 out any attempt at systematic arrangement. 



To prevent any misinterpretation of terms, or confusion 

 of ideas, it will be necessary to make a few preliminary re- 

 marks. The researches of Sir John Herschel and others 

 most distinctly prove that the Light, Heat and Chemical 

 Power of the solar rays are three distinct classes of phaeno- 



* Communicated by the Chemical Society ; having been read March 3, 

 1845. 



