Chemistry and Physics. 397 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Formation of Ozone by Ultra-violet Light. — Fischer 

 and Braemek, by employing a mercury-vapor lamp with quartz 

 walls, have studied the effect of ultra-violet light upon oxygen. 

 They have found that ozonization takes place if the temperature 

 is not too high, for above 270° ozone is decomposed more rapidly 

 than it is formed. Thorough cooling of the oxygen by means of 

 a water-jacket increased the yield of ozone, while a greater 

 intensity of the light of the lamp also increased the yield to a 

 certain limit and then decreased it, probably on account of the 

 effect of greater heating. Upon doubling the speed ,of the oxy- 

 gen through the apparatus the total amount of ozone formed was 

 nearly doubled, but the percentage of ozone formed was some- 

 what diminished. The authors believe that their experiments 

 show the correctness of Warburg's view, that the formation of 

 ozone by the silent electric discharge is due to the ultra-violet 

 light thus formed. A short time ago one of the authors found 

 that their lamp could produce in a few hours the violet coloration 

 of glass containing manganese, which is effected by sunlight in 

 high mountainous regions in months or years, and in our low 

 regions only after longer periods, because the ultra-violet part of 

 its spectrum is strongly absorbed by the earth's atmosphere. By 

 this absorption of .ultra-violet sunlight by our atmosphere ozone 

 results in the upper layers of air, and when it sinks to lower 

 regions it is decomposed by oxidizable substances. — JBerichte, 

 xxxviii, 2633. h. l. w. 



2. A JVeio Reagent for Nickel. — Heretofore there has been no 

 characteristic and delicate reaction for nickel, particularly in the 

 presence of considerable amounts of cobalt. The most delicate 

 of the known tests is probably the brown color produced by 

 alkali thiocarbonates, but this is interfered with by the presence 

 of cobalt. Tschtjgaeff has recently found that a-dimethyl- 

 glvoxime, 



CH 3 . C( : N . OH) . C( : N . OH) . CH 3 , 



is an extraordinarily delicate and characteristic reagent for the 

 metal under consideration. To make the test, the solution is first 

 freed from any excess of acid by the addition of alkali (prefera- 

 bly an excess of ammonia or sodium acetate solution), then some 

 powdered dioxime is added and the solution is heated to boiling 

 for a short time. If the solution is not exceedingly dilute, a 

 scarlet precipitate is produced at once having the composition 

 NiD . DH 2 , where DH 2 represents dioxime. When very small 

 amounts of nickel are present a yellowish liquid is obtained, 

 from which, after cooling, the red precipitate is deposited after a 

 few minutes, whereby the excess of dioxime which separates at 



