Chemistry and Physics. 461 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Conversion of Ammonia into Nitrites and Nitrates. — It 

 has been known for a long time that when air acts upon metal- 

 lic copper in presence of ammonia solution, a formatiou of am- 

 monium nitrite takes place along w r ith the solution and oxidation 

 of the copper, and it has been found, also, that atmospheric 

 oxygen is taken up by a solution of capric hydroxide in ammonia, 

 with the formation of nitrite. The first of these reactions gives 

 a small yield of nitrite in comparison w T ith the amount of copper 

 oxidized, while the second one takes place very slowly. W. 

 Teaube and A. Biltz have, therefore, investigated the electro- 

 lytic oxidation of ammonia in the presence of cupric hydroxide, 

 and have found that when an ammoniacal solution of sodium 

 hydroxide containing dissolved cupric hydroxide is electrolyzed, 

 nearly all the oxygen liberated at the anode is utilized in convert- 

 ing ammonia into the nitrite. Electrodes of platinum and iron 

 foil w^ere used for the experiments ; the latter being scarcely 

 attacked in the alkaline solutions. When the electrolysis was 

 prolonged it was found that the nitrite was completely oxidized 

 to nitrate. It was found that the process gave a high percentage 

 of efficiency in the use of the electric current on the small scale 

 used in the laboratory, but it has not yet been ascertained that 

 this interesting method will prove economical as a manufacturing 

 process on the large scale. — Berichte, xxxvii, 3130. h. l. w. 



2. Is TyndalVs Optical Method Capable of Showing the 

 Presence of Molecules in Solutions? — It has been shown by 

 Spring that it is possible to obtain aqueous solutions in which a 

 powerful ray of light is invisible, just as Tyndall found, long ago, 

 that such a ray was invisible in properly purified gases. Lobby 

 de Bruyx and Wolff have recently made experiments which 

 seem to indicate that large molecules in solution have an action 

 upon the ray of light which is similar to that of ultramicro- 

 scopic, suspended particles. Their results are perhaps not yet 

 conclusive, but if work on a larger scale and with better apparatus 

 confirms these preliminary results, it will not be easy to distin- 

 guish between real and pseudo-solutions ( e. g. colloidal solutions 

 of metals), by means of the action of light. — Pecueil, Pays-Pas, 

 xxiii, 153. h. l. w. 



3. A New Modification of Silicon. — Moissan and Siemens 

 have found that silicon is more soluble in molten silver than in 

 zinc. It was observed, moreover, that a part of the silicon was 

 readily soluble in hydrofluoric acid, although it separated in a 

 crystalline condition when the silver solidified. Thus, upon 

 saturation, silver was shown to dissolve the amounts given in the 

 following table : 



