8 Professor Draper o?i TitJionized Cklori?ie. 



serve to take place when a feeble light falls on a mixture of 

 chlorine and hydrogen which has been prepared in the dark. 

 A certain space of time elapses before any formation of mu- 

 riatic acid occurs, during which the absorption in question is 

 going on ; and when that is completed, and the mixture is ti- 

 thonized, union of the gases begins and muriatic acid forms. 

 From end to end of the spectrum the action is positive, and 

 differs only in intensity ; but this difference in intensity opens 

 before us new views of the constitution and character of the 

 solar beam. 



University of New York, 

 June 20, 1843. 



The foregoing paper was written almost a year ago, and 

 since that lime I have made several new observations corro- 

 borative of the results given. 



Chlorine is not the only elementary substance in which 

 the rays produce a change. In his chapter on phosphorus, 

 Berzelius remarks, " Light produces in it (phosphorus) a pe- 

 culiar change, of which the intimate nature is unknown ; and 

 which, so far as we can judge at present, does not alter its 

 weight. It makes it take a red tint. This phsenomenon 

 occurs not only in a vacuum, even in that of a barometer, but 

 also in nitrogen gas, in carburetted hydrogen, under water, 

 alcohol, oil and other liquids. When we expose to the sun- 

 light phosphorus dissolved in aether, oil, or hydrogen gas, it 

 instantly separates under the form of red phosphorus; it un- 

 dergoes very rapidly this modification in violet light, or in 

 glass vessels of a violet colour. The light of the sun makes 

 it easily enter into fusion in nitrogen gas, but it does not melt 

 in hydrogen, and in the Torricellian vacuum it sublimes in the 

 form of brilliant red scales." (Berzelius, Traite, tom. i. p. 258.) 



Again, when speaking of phosphuretted hydrogen, he says, 

 " Exposed to the influences of the direct solar light this gas is 

 decomposed, a part of the phosphorus separates under the 

 form of red phosphorus, and is deposited on the interior sur- 

 face of the glass. If we cover the vessel which contains the 

 gas imperfectly, no phosphorus is deposited on the covered 

 spaces." (lb. tom. i. p. 265.) 



As Berzelius does not give these experiments as his own, 

 and 1 do not know to whom we are indebted for them, I re- 

 peated some of them. Among other corroborative results, it 

 appeared, that a piece of phosphorus of a pale or whitish co- 

 lour, in a vessel filled with pure and dry carbonic acid gas, 

 placed in the sunshine, rapidly exhibited the phaenomenon in 

 question. Eventually the phosphorus became of a deep blood- 



