2 Professor Draper on Tithonized Chlorine. 



these things held for a compound substance the iodide of 

 silver (Phil. Mag. Sept. 184.1). 



For reasons which will be obvious as the description pro- 

 ceeds, I shall speak of chlorine which has been exposed to the 

 beams of the sun, as tithonized chlorine. 



I. Description of the experiment. 



In two similar white glass tubes place equal volumes of 

 chlorine, which has been made from peroxide of manganese 

 and muriatic acid by lamplight, and carefully screened from 

 access of daylight. Expose one of the tubes to the full sun- 

 beams for some minutes, or if the light be feeble, for a quarter 

 of an hour : the chlorine which is in it becomes tithonized. 

 Keep the other tube during this time carefully in a dark place; 

 and now, by lamplight, add to both equal volumes of hydro- 

 gen gas. These processes are best carried on in a small por- 

 celain or earthenware trough, filled with a saturated solution 

 of common salt, which dissolves chlorine slowly; and to avoid 

 explosions operate on limited quantities of the gases. Tubes 

 that are eight inches long and half an inch in diameter will 

 answer very well. The two tubes now contain the same 

 gaseous mixture, and only differ in the circumstance that one 

 is tithonized and the other not. Place them therefore side by 

 side before a window, through which the entrance of daylight 

 can be regulated by opening the shutter ; and now, if this part 

 of the process is conducted properly, it will be seen that the 

 tithonized chlorine commences to unite with the hydrogen, 

 and the salt water rises in that tube. But the untithonized 

 chlorine shows no disposition to unite with its hydrogen, and 

 the liquid in its tube remains motionless for a long time. Fi- 

 nally, as it becomes slowly tithonized by the action of the day- 

 light impinging on it, union at last takes place. From this, 

 therefore, we perceive that chlorine which has been exposed 

 to the sun will unite promptly and energetically with hydro- 

 gen ; but chlorine that has been made and kept in the dark 

 shows no such property. 



As I doubt not this remarkable experiment will be repeated 

 by chemists, I will add that the only point to which attention 

 in particular is to be given, is in the final exposure to the 

 light. This must not be too feeble, or the action will be te- 

 dious; but the direct sunbeam must be sedulously excluded, 

 or an explosion will result. A room illuminated by one small 

 window, looking to the north, answers very well. It need 

 scarcely be added that care must be taken that both tubes are 

 illuminated alike. 



