August 7^ 19 19] 



NATURE 



44: 



A few decades ago the majority of these bodies 

 then known were regarded in the light of 

 "chemical curiosities" rather than as potentially 

 useful products. They were interesting to the 

 student on account of their theoretical signifi- 

 cance, but had little practical value. The present 

 generation has seen all this changed. There is 

 scarcely one of the commoner gases and few 

 even of the rarer ones that have not been turned 

 to a useful account. It is unnecessary to multiply 

 instances of this fact. The examples of oxygen, 

 nitrogen, chlorine, carbonic acid, nitrous oxide, 

 ammonia, acetylene, ethylene, and methane are 

 familiar enough to everybody. Others might be 

 named. And the process goes on. When argon 

 was discovered it seemed inconceivable, from the 

 very nature of its inertness, that it could be of 

 any practical use. But now argon is being ex- 

 tracted from the atmosphere on a manufacturing 

 scale and applied in the electric lighting industry. 

 Attempts are being made to utilise helium, and 

 it is only the extremely limited supply which 

 prevents the application of its extraordinary pro- 

 perties on the large scale. We may yet live to 

 see the widespread use of niton as a therapeutic 

 agent. In fact, he would be rash who would 

 attempt to set any limit to the possible utilitarian 

 application of a chemical product. History teems 

 with examples which should warn us of the un- 

 wisdom of indulging in any such restriction. 



Among the several gases which have of late 

 years received an extraordinary development of 

 application is hydrogen — the subject of Major 

 Litherland Teed's little book. Although one of 

 the earliest of the gases to have its individuality 

 clearly recognised — namely, by Cavendish, who 

 in 1766 made an approximately accurate estima- 

 tion of its lightness — it received no application, 

 except as an occasional chemical reagent, until 

 it replaced the expanded air of Montgolfier's fire- 

 balloon, and this remained its chief use until coal- 

 gas became more generally available for aero- 

 static purposes. In war-time, however, hydrogen, 

 for obvious reasons, was still employed for the 

 inflation of balloons, and much of the develop- 

 ment of the technology of hydrogen has resulted 

 from war-time necessities. Many manufacturing 

 processes, in fact, owe their origin entirely to the 

 enormous demand for the hydrogen required to 

 fill kite balloons and airships. The knowledge 

 and experience thus gained are directly available 

 for the ever-growing applications of hydrogen in 

 the chemical arts, as, for example, in the syn- 

 thesis of ammonia, and in the hardening of oils 

 and fats by catalytic agencies, both of which pro- 

 cesses have now become highly important 

 chemical industries. What the future of synthetic 

 ammonia will be remains to be seen. As yet 

 its production has made comparatively little pro- 

 gress in this country, but the "coal question " is 

 bound to affect its prospects, and to what extent, 

 if any, synthetic ammonia will replace by-product 

 ammonia is not wholly clear. On the other hand, 

 the application of M. Sabatier's cardinal dis- 

 covery of the effect of hydrogen, under the influ- 

 NO. 2597, VOL. 103] 



ence of metallic catalysts, in transforming oils 

 and other unsaturated fats into edible products 

 has solved a very pressing problem, which threat- 

 ened at one time to become acute. It has been 

 the means of adding enormously to the food 

 supply of the world. 



Major Teed's monograph consists of five com- 

 paratively short chapters. In the first two he 

 gives a concise account of the physical and 

 chemical properties of the gas, the mode of its 

 discovery, the manner of its occurrence 'in Nature 

 in the free or occluded state, and its reactions 

 with other chemical elements and with certain 

 compounds, particularly with animal and vege- 

 table oils. There is necessarily little of novelty in 

 these chapters; their material is, for the most 

 part, the common property of the text-books. 

 Certain of the physical constants of hydrogen, 

 such as its thermal values, density, solubility 

 in water, transpiration, refractivity, and the rela- 

 tionship between its pressure and volume, are 

 referred to an appendix. These matters are, 

 however, dealt with as briefly as possible; it was 

 doubtless considered necessary to treat them 

 as completing the descriptive history of the 

 subject. The account is generally accurate, and 

 bibliographical references are freely given. We 

 would, however, remark that Sir William 

 Crookes's name is wrongly spelled on p. 7 ; 

 "Moisson" (p. 19) should be printed "Mois- 

 san"; "Neuman" and "Strientz" should be 

 "Neumann" and "Streintz. " Moreover, in the 

 table, p. 15, giving the volume of hydrogen 

 adsorbed by finely divided metals, it should be 

 stated that the amounts are maximum values ; 

 the amounts actually adsorbed are frequently 

 much less in many cases. 



TTie most generally interesting and most valu- 

 able section of the work is concerned with the 

 manufacture of hydrogen on the large scale. 

 This is dealt with in the remaining chapters. The 

 processes in use are to some extent affected by 

 local conditions. This is especially true of 

 hydrogen to be used for aviation in war. But 

 when the gas is to be employed for manufacturing 

 purposes, and cost, ease, purity, and uniformity 

 of production are important considerations, war- 

 time methods are not necessarily to be preferred, 

 and as a matter of fact these are seldom or never 

 employed in industry. Manufacturing methods 

 are purely chemical, purely physical, or chemico- 

 physical. The choice of a particular method must 

 depend upon the amount of the gas required, the 

 use to which it is to be put, facility of transport, 

 etc. In certain circumstances it may be better 

 to buy the hydrogen than to make it on the spot. 

 In some established industries, as in the electro- 

 lytic production of chlorine and caustic soda, 

 hydrogen is a by-product, and its collection in- 

 volves little additional cost; hence it can be 

 obtained relatively cheaply. In other cases it 

 may be preferable to establish a plant for its pro- 

 duction. This may be electrolytic, or it may 

 depend upon the separation of hydrogen from 

 "blue " water-gas by metallic iron, or by the 



