April ii, 191 8] 



NATURE 



107 



strains in the vicinity, as may be produced by 

 le welding. 



'hermit welding finds its chief application in 



irork on large sections, such as rails and thick 



shafts. In welding together the ends of two con- 



lutive rails, for example, the rails are made to 



uch, and a refractory mould is placed round the 



iwo ends. The thermit mixture, consisting of 



uowdered aluminium and oxide of iron, is fired in 



crucible by the ignition of a small quantity of 



mixture of barium peroxide and aluminium, the 



action resulting in the production of aluminium 



\ide and metallic iron at a temperature of about 



500° C. The molten mass is run from the crucible 



into the mould, the quantity being such that the 



lower part of the rails is surrounded by molten 



iron and the upper part by the fused alumina. 



After a short time longitudinal pressure is applied 



10 the rails, which are now at a welding heat, and 



complete union is secured. After removing the 



mould, the thermit iron is left adhering to the- 



lower part of the joint and the slag broken away 



from the upper part. This is now the common 



method of welding rails, and forms a typical 



example of the use of thermit. 



In comparing the various methods of welding, 

 it may be said that each has its special advan- 

 tages and is preferable for one kind of work. 

 \\'hen a choice has to be made in a case in which 

 the work could be executed by several methods, 

 the user is guided by experience as to which is 

 likely to suit best, and also by cost and conveni- 

 ence. In all instances much depends upon the 

 skill of the welder, and figures showing the 

 strength of welds will not be realised in practice 

 unless the work is carried out by a thoroughly 

 competent workman. ^ C. R, D. 



SULPHURIC ACID AND THE WAR. 

 IV/rODERN warfare has been described as an 

 ■'■*^-»- affair of mechanics and chemistry. Of 

 course, this is a very partial and incomplete defini- 

 tion, inasmuch as it neglects what, after all, is 

 the paramount factor — the human element. But, 

 given that the human factor is equally potent on 

 both sides, it is certainly true that the belli- 

 gerent which is most alert and most resourceful in 

 the use of the methods and practical achievements 

 of science will inevitably triumph in the end. The 

 whole conduct of the war shows that our enemies 

 have not been slow to appreciate this fact, and if 

 we have been a little more tardy in learning the 



. same lesson we are rapidly making good what- 



[ ever leeway we may have lost. 



Nothing distinguishes this war more markedly 

 from previous campaigns than the manner in 

 which the scientific knowledge and intelligence of 

 the nation have been enlisted, both in its prosecu- 

 tion and in the repair of its ravages. We have 

 notable instance of this circumstance in the 

 cently published Report of the Departmental 

 Committee appointed to consider the post-war 



f position of the sulphuric acid and fertiliser trades. 

 Sulphuric- acid is indispensable in war; a nation 

 NO. 2528, VOL. lOl] 



deprived of it, or of certain of the products which 

 can be obtained only by its means,' would be help- 

 less in face of its enemies. It required, however, 

 nearly nine months of actual warfare for those in 

 authority in this country to realise the danger of a 

 possible shortage in the supply of the sulphuric 

 acid absolutely essential to the production of ex- 

 plosives, and a small but eminently competent 

 committee of well-known manufacturers was at 

 length appointed to advise the Government in the 

 matter. The result was that the makers of sul- 

 phuric acid and its principal users were organised 

 in view of the national emergency. The request 

 that the demands of the explosive factories should 

 receive priority was willingly acceded to, and it 

 is satisfactory to learn that their requirements 

 were fully met. 



The enormous amount of sulphuric acid of high 

 strength needed in the manufacture of explosives 

 has, however, led to an extraordinary development 

 in the industry, and to many far-reaching changes 

 which those who are charged with the considera- 

 tion of questions of what is termed "reconstruc- 

 tion " view with no little apprehension and con- 

 cern. Concentrating plants on a large scale have 

 been everywhere erected ; large oleum plants have 

 been constructed in connection with Government 

 factories, and private manufacturers have been 

 encouraged to extend their chamber plants and 

 to work them continuously and intensively. The 

 result is that the productive power of the country 

 has now reached an amount greatly in excess of 

 the pre-war consumption, and the problem which 

 the Committee has had to consider is how this 

 expansion can be dealt with in view of possible 

 post-war requirements. 



If the outcome of the war is to lead to the 

 continued existence of militarism, the Government 

 explosive factories with their contact and oleum 

 plants will have to be maintained, for it is incon- 

 ceivable that we shall revert to the fatuous 

 policy of letting things take care of themselves, 

 and of not foreseeing and making provision in 

 advance, which prevailed at the outbreak of 

 hostilities. As regards private manufactories of 

 concentrated acid and oleum, it is to be expected 

 that the resuscitation of the synthetic dye industry 

 in this country will continue to absorb an increas- 

 ing amount of these products. We may hope that 

 it will prove to be one more instance of a super- 

 fluity in supply creating a new demand. But, 

 however optimistic one may be in this respect, 

 it can scarcely be doubted that for some time to 

 come the supply will greatly exceed the demand, 

 and that much plant will lie idle and may possibly 

 be "scrapped." 



There is at least one new source of sulphurjc 

 acid in this country, created by the war, which 

 it is greatly to be hoped will be maintained and 

 extended, and that is the production of acid from 

 Australian zinc concentrates. The manufacture of 

 zinc was instituted in this country before it was 

 started in Belgium and Germany, but it has not 

 been developed here to anything like its proper 

 extent. Although London is the chief zinc market 



