368 TRANSACTIONS OF SECTION B. 



properties of aluminium, now obtainable at a moderate price, in the various 

 operations classed under the heading alumino-thermy, the most important being 

 the reduction of refractory metallic oxides, although, of course, thermite is 

 useful for the production of high temperatures locally. 



The modern methods of liquefying gases, which have been developed within 

 the period under review, have rendered possible research work of absorbing 

 interest on the effect of very low temperatures on the properties and chemical 

 activity of many substances, and have been applied, for instance, in separating 

 from one another the members of the argon family, and in obtaining ozone in 

 a state of practical purity. Moreover, industrial applications of these methods 

 are not lacking, amongst which I may mention, the separation 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 inorganic and organic substances, and older processes are being displaced 

 by these modern rivals in steadily increasing number. It is sufficient to refer 

 to the preparation of sodium, magnesium, calcium, and aluminium, by electro- 

 lysis 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 alkalis (and simultaneously of 

 chlorine), of hypochlorites, chlorates, and perchlorates, of hydrosulphites, of 

 permanganates and ferricyanides, of persulphates and percarbonates ; the regene- 

 ration of chromic acid from chromium salts ; the preparation of hydrogen and 

 oxygen. As regards organic compounds, we find chiefly in use electrolytic 

 methods of reduction, which are specially effective in the case of many nitro 

 compomids, and of oxidation, 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 

 catalytic methods "to industrial purposes. Some processes of this class have, 

 of course, been in use for a considerable tune, for example the Deacon chlorine 

 process and the contact method for the manufactiu-e 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 sulphuric acid with 

 the assistance of mercuric sulphate as catalyst, is no novelty. More recent are 

 the contact methods of obtaining ammonia by the direct combination of nitrogen 

 and hydrogen, and of oxidising ammonia to nitric acid — both of which are eaid 

 to be in operation on a very large scale in Germany. The catalytic action of 

 metals, particularly nickel and copper, is utilised in processes of hydrogena- 

 tion — for example," the hardening of fats, and of dehydrogenation, as in the 

 preparation of acetaldehyde from alcohol, and such metallic 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 sulphate in 

 electrolytic oxidations of carbon compounds, gelatine in the preparation of 

 hydrazine from annnonia, sodium in the synthesis of rubber, &c. 



Other advances in manufacturing chemistry 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, vanadiu)n, tungsten, and tantalum, now used in metal- 

 lurgy or for electric-lamp filaments ; thoria and ceria in the form of mantles 

 for^ incandescent lamps ; pyrophoric alloys of ceriiun and other metals ; zirconia, 

 which appears to be a most valuable refractory material; and compounds of 

 radium and of mesothorium, for medical use as well as for research. Hydrogen, 

 together with oxygen and nitrogen, are in demand for synthetic purposes, 

 an'd the first also for lighter-than-air craft. Ozone is considerably used for 

 sterilising water and as an oxidising agent, for example in the preparation of 

 vanillin from isoeugenol, and hydrogen peroxide, now obtainable very pure in 

 concentrated solution, and the peroxides of a number of the metals are also 

 utilised in many different ways. The per- acids— perboric, percarbonic, and 

 persulphuric— or their salts are employed for oxidising and bleaching purposes, 

 and sodium hvdrosulphite is much in demand as a reducing agent— e.;/., in 



