THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[THIRD SERIES.] 



JULY 184-4. 



I. On Tithonized Chlorine. By John William Draper, 

 M.D., Professor of Chemistry in the University of New 

 York. 



[The following paper was read at the meeting of the British Association, 

 held at Cork last year (1843), I have added to it, in an Appendix, some 

 further observations subsequently made. — J. W. D.] 



/CHLORINE gas, which has been exposed to the daylight 

 ^^ or to sunshine, possesses qualities which are not pos- 

 sessed by chlorine which has been made in the dark. 



This is shown by the circumstance, that chlorine which has 

 been exposed to the sunshine has obtained from that expo- 

 sure the property of speedily uniting with hydrogen gas; a 

 property not possessed by chlorine whicli has been made and 

 kept in the dark. 



This quality gained by the chlorine arises from its having 

 absorbed tithonic rays corresponding in refrangibility to the 

 indigo. It is not a transient, but apparently a permanent 

 property, the rays so absorbed becoming latent, and the effect 

 lasting for an unknown period of time. The facts which I 

 shall proceed to describe will be interesting to chemists, be- 

 cause they plainly lead us to suspect that the descriptions we 

 have of the properties of all elementary and compound bodies 

 are either inaccurate or confused. These properties are such 

 as bodies exhibit after they have been exposed to the light ; 

 we still require to know what are the properties they possess 

 before exposure to such influences. 



Natural philosophers will also find an interest in these phae- 

 nomena, for they finally establish for the tithonic rays two im- 

 portant facts, — 1st, that those rays are absorbed by ponder- 

 able bodies ; and 2nd, that they become latent after the man- 

 ner of heat. Some years ago I endeavoured to prove that 



Phil. Mag. S. 3. Vol. 25. No. 163. July 1844. B 



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