RECENT ADVANCES IN SCIENCE 445 



them here. In order that the solution of thiosulphate may 

 remain alkaline until the whole of the thiosulphate has been 

 decomposed by chlorine, it is necessary to have present 

 Na 2 C0 3 .ioH 2 in slight excess. A satisfactory formula for a 

 respirator is 5 :6 : 10 of thiosulphate, crystallised carbonate, and 

 water respectively. Sel r oints out that with the formula of 

 the Paris Academy of Medicine, the solution becomes acid 

 when only 35 per cent, of the thiosulphate has been decom- 

 posed. 



Catalysts. — The search for substances which will act as 

 specific catalysts is being prosecuted with increasing vigour, 

 as the need for more economical processes in industrial work 

 becomes greater. To this end, more and more attention is 

 being directed to the rarer inorganic substances, such as the 

 metals and compounds of the rare-earth and platinum groups. 

 The Badische Anilin und Soda Fabrik have lately patented 

 (D.R.P. 275518) the use of ruthenium, its oxides and salts to 

 catalyse certain oxidation processes. With asbestos and 

 potassium ruthenate, methyl alcohol in presence of air readily 

 forms formaldehyde at 120 C, whilst a red heat is necessary 

 in the cases of platinum, palladium, and iridium. With hydro- 

 carbons, where air is unsuitable, ordinary oxidising agents 

 such as chlorate can be utilised successfully when a trace of 

 a ruthenium salt is present. 



In the classical researches on ammonia, descriptions of 

 which are now appearing (Z. Electrochem. 191 5, 21, 191), 

 Haber and his co-workers have made very frequent use of 

 catalysts, and have investigated their actions in a systematic 

 manner. Iron and osmium are specific catalysts for the 

 decomposition of ammonia, whilst uranium acts as a synthetic 

 catalyst. Uranium . carbide was used, but the active agent 

 appears to be Ur 3 N 4 which is formed gradually, best of all 

 from the carbide, although other derivatives give the effect. 

 High pressure and a temperature about 500 C. are the other 

 requisite conditions for the optimum reaction of the mixed 

 nitrogen and hydrogen gases. 



Analysis. — The well-known brown ring qualitative test for 

 nitrates is liable to be vitiated when halide salts, more espe- 

 cially bromide and iodides, are present. Consequently the 

 new test devised by Tingle (/. Soc. Client. Indust. 191 5, 34, 

 393) of the same order of delicacy, but which is reliable in 



