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SCIENCE 



[N. S. Vol. XLIV. No. 1135 



tical purity. Moreover, industrial applica- 

 tions of these methods are not lacking, 

 amongst which I may mention the separa- 

 tion of nitrogen and oxygen from air, and 

 of hydrogen from water-gas — processes 

 which have helped to make these elements 

 available for economic use on the large 

 scale. 



Electrolytic methods are now extensively 

 employed in the manufacture of both inor- 

 ganic and organic substances, and older 

 processes are being displaced by these mod- 

 ern rivals in steadily increasing number. 

 It is sufficient to refer to the preparation of 

 sodium, magnesium, calcium and alumi- 

 num, by electrolysis of fused compounds of 

 these metals ; the refining of iron, copper, 

 silver and gold; the extraction of gold and 

 nickel from solution; the recovery of tin 

 from waste tin-plate; the preparation of 

 caustic alkalies (and simultaneously of 

 chlorine), of hypochlorites, chlorates and 

 perchlorates, of hydrosulphites, of per- 

 manganates and ferricyanides, of persul- 

 phates and perearbonates ; the regenera- 

 tion of chromic acid from chromium salts ; 

 the preparation of hydrogen and oxygen. 

 As regards organic compounds, we find 

 chiefly in use electrolytic methods of re- 

 duction which are specially effective in the 

 case of many nitro compounds, and of oxi- 

 dation, as for instance the conversion of 

 anthracene into anthraquinone. At the 

 same time a number of other compounds, 

 for example iodoform, are also prepared 

 electrolytically. 



"Within recent years there have been 

 great advances in the application of cata- 

 lytic methods to industrial purposes. 

 Some processes of this class have, of course, 

 been in use for a considerable time, for ex- 

 ample the Deacon chlorine process and the 

 contact method for the manufacture of 

 sulphuric acid, whilst the preparation of 

 phthalic anhydride (largely used in the 

 synthesis of indigo and other dyestuffs), by 



the oxidation of naphthalene with sul- 

 phuric acid with the assistance of mercuric 

 sulphate as catalyst, is no novelty. More 

 recent are the contact methods of obtain- 

 ing ammonia by the direct combination of 

 nitrogen and hydrogen, and of oxidizing 

 ammonia to nitric acid — both of which are 

 said to be in operation on a very large scale 

 in Germany. The catalytic action of met- 

 als, particularly nickel and copper, is util- 

 ized in processes of hydrogenation — for ex- 

 ample, the hardening of fats, and of de- 

 hydrogenation, as in the preparation of 

 acetaldehyde from alcohol, and such me- 

 tallic oxides as alumina and thoria can be 

 used for processes of dehydration — e. g., 

 the preparation of ethylene or of ether 

 from alcohol. Other catalysts employed in 

 industrial processes are titanous chloride 

 in electrolytic reductions and cerous sul- 

 phate in electrolytic oxidations of carbon 

 compounds, gelatine in the preparation of 

 hydrazine from ammonia, sodium in the 

 synthesis of rubber, etc. 



Other advances in manufacturing chem- 

 istry include the preparation of a number 

 of the rarer elements and their compounds, 

 which were hardly known thirty years ago, 

 but which now find commercial applications. 

 Included in this category are titanium, 

 vanadium, tungsten and tantalum, now used 

 in metallurgy or for electric-lamp fila- 

 ments; thoria and ceria in the form of 

 mantles for incandescent lamps ; pyrophoric 

 alloys of cerium and other metals ; zirconia, 

 which appears to be a most valuable re- 

 fractory material; and compounds of 

 radium and of mesothorium, for medical 

 use as well as for research. Hydrogen, to- 

 gether with oxygen and nitrogen, are in 

 demand for synthetic purposes, and the 

 first also for lighter-than-air craft. Ozone 

 is considerably used for sterilizing water 

 and as an oxidizing agent, for example in 

 the preparation of vanillin from isoeugenol 

 and hydrogen peroxide, now obtainable 



