INFLUENCE OF LIGHT. 135 



in sunshine, than in the diffused light of day ; but 

 there is nothing more in this than the similar 

 action which light exercises on ordinary chemical 

 combinations, it merely accelerates in a greater or 

 less degree the action already subsisting. 



Chlorine and hydrogen combining form muriatic 

 acid. This combination is effected in a few hours 

 in common daylight, but it ensues instantly with a 

 violent explosion, under exposure to the direct 

 solar rays, whilst not the slightest change in the 

 two gases takes place in perfect darkness. When 

 the liquid hydrocarburet of chlorine, resulting 

 from the union of the olefiant gas of the Dutch 

 chemists with chlorine, is exposed in a vess'el with 

 chlorine gas to the direct solar rays, chloride of 

 carbon is immediately produced ; but the same 

 compound can be obtained with equal facility in 

 the diffused light of day, a longer time only being 

 required. When this experiment is performed in 

 the way first mentioned, two products only are 

 observed (muriatic acid and per chloride of carbon); 

 whilst by the latter method, a class of intermediate 

 bodies are produced, in which the quantity of 

 chlorine constantly augments, until at last the 

 whole liquid hydrocarburet of chlorine is converted 

 into the same two products as in the first case. 

 Here,, also, not the slightest trace of decomposition 

 takes place in the dark. Nitric acid is decomposed 

 in common daylight into oxygen, and peroxide of 

 nitrogen and chloride of silver becomes black in 



