430 Scientific Intelligence. 



methyl chloride, at the ordinary pressure. — Ann. Chem. Phys., 

 VI, xxv, 125, Jan., 1S92. G. F. b. 



2. On the Expansion of Chlorine in Violet Light. — The 

 observation of Budde in 1ST I that chlorine sutlers an expansion 

 in volume on exposure to blue or violet light, has been confirmed 

 by Richardson who finds that this expansion is independent of 

 the heating effect produced, and that it remains constant if the 

 light is invariable, returning to its original volume when the 

 light is cut off. By means of a differential apparatus, consisting 

 of two glass tubes 10 cm long and of 55 c. c. capacity, connected 

 to a graduated horizontal gauge having a small bulb at each end, 

 this expansion was compaied with the intensity of the light as 

 determined with a Bunsen and Roscoe pendulum actinometer. 

 The gauge and bulbs contained strong sulphuric acid, a bubble 

 of air in the former serving as index. When these tubes, placed 

 in a suitable box were turned so as to face the sun, it was found 

 that when they both contained air, they were equally heated; 

 but that when one of them was filled with dry chlorine, the 

 expansion was greater upon this side. When the index became 

 stationary the light-intensity was measured ; and it was found 

 that the change in the volume of the chlorine was very closely 

 proportional to the intensity of the blue rays. By suspending 

 such a differential apparatus on the beam of a balance so that 

 the flow of acid from one side to the other caused this beam to 

 move, a continuous registering apparatus was constructed by the 

 author, the motion of the beam being communicated to a pen 

 which produced a record on a revolving drum. — Phil. Mag., V, 

 xxxii, 277, Nov., 1891. g. f. b. 



3. On the Dissociation of liquid Nitrogen peroxide. — Ostwald 

 has applied the generalization of Van 't Hoff, that dissolved sub- 

 stances obey the same laws as gases, to the data obtained by 

 Cundall in a research upon the dissociation which nitrogen per- 

 oxide undergoes when dissolved in chloroform; expecting that 

 the laws of dissociation of binary compounds such as this which 

 are well known in the gaseous state, will also hold good for the 

 dissolved peroxide. Representing by the equation ar/(l — x) = Ky 

 the law of dissociation in the gaseous state, in which x is the 

 amount of dissociated peroxide, v the volume of unit mass and K 

 a coefficient constant with the temperature, the author obtains 

 from Cundall's figures y= 100/c and x = 0'000468r, where c is 

 the concentration and r the relative amount of N0 2 produced. 

 Substituting these values the equation becomes , 000468r 2 .c 

 /l — 0-00046Sr= 100K. And since K is constant when the tem- 

 perature does not change, the first member must be also constant. 

 The value of K- as given from Cundall's figures varies from 

 2-13 X lO - " 1 to 3-12 X 10~ 7 , the latter value being that at the 

 highest concentration, and one at which Van 't Hoff's law can 

 hardly be expected to hold with exactness. Hence it appears 

 that nitrogen peroxide does in fact dissociate according to the 

 same law whether it be in dilute solution or in the gaseous state, 



