Chemistry and Physics. 67 



electrolysis. The experiments were made by passing an alternat- 

 ing current through an ordinary non-inductive resistance and 

 through an electrolyte, the difference of potential at the extremi- 

 ties of these two resistances being measured at different phases 

 of the current. Accompanying the paper are curves of current 

 and potential differences with different frequencies, and also curves 

 showing the dissipation of energy per cycle. As a result it ap- 

 peared that with platinum electrodes 150 sqcm . in area, the ion 

 being hydrogen, the maximum electromotive force due to polari- 

 zation was reached when one-tenth of a coulomb had passed 

 through the cell. That is to say, when O'OOOOl gram of hydi-o- 

 gen had been liberated. It appears therefore that 0*00000007 

 gram of hydrogen is sufficient to polarize one square centimeter 

 of platinum. If we may assume the density of this hydrogen to 

 be comparable with that of liquids, the thickness of the film of 

 hydrogen necessary is of the same order as this number — 

 0-00000007 cm — a number comparable with the distance between 

 the molecules. — Proc. Hoy. iSoc, liv, 407 ; J. Chem. JSoc, lxvi, ii, 

 178, May, 1894. G. F. b. 



4. On the Source of the Hydrogen Peroxide in the Atmosphere. 

 — From his experiments, Bach has been led to the conclusion that 

 under the action of sunlight carbonic acid undergoes decomposi- 

 tion, yielding percarbonic acid and the elements of formaldehyde 

 according to the equation 



(H a CO,),= (H,CO 4 ), + |0 + H s O 



The percarbonic acid may subsequently decompose, yielding car- 

 bon dioxide and hydrogen peroxide H 2 C0 4 = C0 2 + H 2 2 . It is 

 to these reactions in his opinion, that the presence of hydrogen 

 peroxide in the atmosphere is due. If a cold saturated and fil- 

 tered solution of uranium acetate, containing one per cent of 

 freshly distilled diethylaniline, be exposed to the simultaneous 

 action of carbon dioxide and strong sunlight, a violet coloration 

 is developed ; although the solution is not thus affected by either 

 of these agents separately. The result, therefore, must be due, 

 the author believes, to the production of formaldehyde and of a 

 compound (percarbonic acid) which will oxidize the leuco-base 

 produced by the action of the formaldehyde upon the diethylani- 

 line. — JBer. Berl. Chem. Ges., xxvii, 340, February, 1894. 



G. F. B. 



5. On the Explosive Haloid Compounds of Nitrogen. — Pure 

 niti*ogen trichloride NC1 3 was first prepared by Gattermann in 

 1888, as an oily liquid, so explosive that sunlight or even the light 

 of burning magnesium caused its detonation. Associated with it, 

 the crude product contained other chlorides of nitrogen. Last 

 year Szuhay produced the compounds NHI 2 and NAgI 2 , both ex- 

 plosive. The whole subject has now been stLdied by Seliwanow 

 who shows that the production of the chloride or the iodide of 

 nitrogen by the action of the halogens upon ammonia takes 



