;62 



NA rURE 



[August 8, 1901 



reduced metal is volatilised it soon condenses, and may be 

 collected, usually in an oxidised form. 



In using aluminium as fuel the object, of course, is to produce 

 intense heat, and returning to this mass of iron ore from the 

 Surrey heath it may at once be stated that an oxide of iron. 



3000° C. The aluminium plays the part of a fuel, and this table 

 shows the advantage aluminium possesses as compared with 

 carbon for the particular work required of it.^ 



The Reduction of FCoOs to Iron by Ahiminium and by Carbon. 

 Aluminium. Carbon. 

 Compound produced ... AUO^ CO 



Amount of reducing 

 agent required to pro- 

 duce I kilo, of iron ... 0'4S4 kilo. 0'32i kilo. 

 Amount of heat pro- 

 duced by oxidation of 

 the reducing agent ... 3456calories 77ocalories 



Heat required to reduce 



the Fe.jOj 1796 „ 1796 ,, 



Heat required for fusion 



of the slag 548 ,, 



Heat required for fusion 



of iron ... ... 362^ 



Total heat required ... 2 706 ,, 179^ ,, 



Residual heat available 750 ,, —1026 ,, 



erric oxide, is the most convenient oxide to use, partly because 

 it is inexpensive. 



Many of my audience already know that the recent 

 investigations having for their object the use of aluminium 

 as a source of heat have been conducted by Dr. Hans 

 Goldschniidt, of Essen, and it is through his 

 labours that metallurgy enters upon an entirely 

 new phase. It would be difficult to offer liim 

 fuller or more unstinted praise than that. Vou 

 will, I trust, soon realise how much industry is 

 indebted to him. In its simplest form his process 

 consists in igniting a mixture of oxide of iron, 

 ferric oxide and finely divided aluminium. To 

 this mixture the name of "thermit" has been 

 given, and several varieties of it, adapted to 

 various kinds of work, are used by Dr. Gold- 

 schniidt at the works of the Allgemeine Thermit- 

 Gesellschaft at Essen-Ruhr. 



The mixture is placed inside a crucible (Fig. 2) 

 and is ignited by a small piece of magnesium wire, 

 which serves as a kind of wick if it is placed in 

 a little heap of calcium sulphate and aluminium. 

 Such a mass will now be lighted, and you see 

 intense heat is produced. [When the operation "'^ ■*'" " ^'" 

 was conducted in accordance with the above in- 

 dications, the theatre was brilliantly illuminated by the intense 

 light produced. A mass of metallic chromium weighing about 

 100 lbs., reduced to the metallic slate as above described, was 

 exhibited.] The aluminium abstracts oxygen from the oxide of 

 iron and a sufficiently intense heat is produced not only to melt 



On the aluminium side some 750 calories {units 

 ^^"- of heat) are available to do work {3456 - 2706 



= 750 calories). On the carbon side there is a de- 

 ficiency of no less than — 1026 calories. As regards the crucibles, 

 they may be made of alumina, the solid product which is the result 

 of the combustion of aluminium. They may also be made of mag- 

 nesia or mended with magnesia. I shall have more to say about 

 the solid product of the combustion subsequently. The practical 



Fig. 5. — Casing packed 



the iron which is liberated from its oxygen, but to melt up the 

 slag and, further, to leave a considerable surplus of heat, which 

 is available for doing other work. No known pyrometer will 

 enable the heat to be measured. I believe it to be about 



elJecl 



application of the process is as follow.s. The ignited and moltei> 

 mass in the crucible is so intensely hot that it may be made to 

 unite surfaces of steel that require to be joined, such as the ends 

 of lengths of rails. If I may use a simile which enables me to 

 describe the method rapidly, the fluid contents of the crucible 

 are applied as a hot bandage might be applied to 

 « nunded or severed surfaces in the human body 

 \hich require medical treatment to facilitate 

 healing or to cause them to unite. It ni.iy be 

 objected that the fluid contents of the crucible 

 would set as a whole round the metallic junction 

 and give trouble, but this is not the case, for a layer 

 of fluid alumina appears both to coat the rod, tube 

 or rail which has to be welded, and to set in a mass 

 which can be readily detached after the work is 

 done. The casings (Figs. 4 and 5) are protected in 

 the same way. The diagrams (Figs. 3, 4, 5,1 need 

 \ ut little comment, as they sufficiently indicate 

 the method adopted in the case they represent. 

 These figures were used to illustrate a paper by 

 Mr. E. F. Lange (Journal of the Iron and Steel 

 Institute, I900,"No. ii. p. 191). [I was indebted 

 to him for the loan of small appliances of a 

 similar kind to enable me to demonstrate to the 

 audience the welding of steel tubes, and the 

 operation was shown on as large a scale as safety would 



1 These data are from a paper by Prof. K 

 reicliticlu- Zcilschrlft flir Berg- und lluttct 



NO. 1658, VOL. 64] 



