Professor Draper on Tithonized Chlorine. 3 



II. The change in the chlorine is not transient. 



Now it might be supposed that this apparent exaltation of 

 the electro-negative properties of the chlorine is only a trans- 

 ient thing which would speedily pass away, the gas reverting 

 to its original untithonized condition. 



To show that this is not so, tithonize some chlorine in a 

 tube as before. Place it for an hour or two in the dark along 

 with the tube of untithonized chlorine, with which it is to be 

 compared ; then to both add hydrogen. Expose them as in 

 the former experiment to the daylight, and the result will turn 

 out as before, the tithonized chlorine forming muriatic acid at 

 once, and the untithonized refusing to do so. 



This, therefore, shows that the change which the sunbeams 

 impress upon chlorine is to a certain extent a permanent 

 change, and, unlike a calorific effect, it does not spontaneously 

 and rapidly pass away. 



III. There are two stages in the j)h(Enomenon. 



Let us now proceed to make inquiry into the nature of the 

 change thus impressed on the chlorine. This, 1 shall show, 

 rests in the circumstance of the absorption of rays which cor- 

 respond in refrangibility to the indigo, and which appear to 

 become latent. 



In a tube, over salt water, mix together equal volumes of 

 untithonized chlorine and hydrogen gas. Expose it to the 

 daylight, marking the time at which the exposure commences. 

 Watch the level of the liquid in the tube narrowly, and, though 

 stationary for a considerable time, after a certain period has 

 elapsed it will be seen on a sudden to start and commence 

 rising. Observe now how far it will rise during a period 

 which is equal to the time that elapsed between the first ex- 

 posure and the beginning of the rise, and it will be seen that 

 one-fourth or half the gases will disappear. 



It is obvious that from the first moment of exposure the 

 rays must have been exei'ting their influences on the mixture. 

 As will presently be proved, absorption has been all along 

 taking place. There are, therefore, two distinct phsenomena 

 exhibited by this experiment. There is a period during which, 

 though large quantities of the dark rays are disappearing, no 

 visible change is produced ; there is a second period, during 

 which absorption is accompanied by a remarkable chemical 

 effect, the production of muriatic acid. From these things 

 we gather that a definite amount of the tithonic rays must 

 disappear and become latent before muriatic acid can form. 

 The phsenomenon is not unlike that of the disappearance of a 

 definite quantity of heat in the passage of ice into the condi- 

 tion of water, 



B2 



