Figure i. 



Titanium " tliennit " in foundry worl<. 

 iHcatinfj "thermit" tin nver the ladle before in^;ertion.l 



of water added to a mixture of ahnniniuni and 

 sodium peroxide causes it to react : but //; vacuo tiie\' 

 found it to cause merely a sHght effervescence.* 



II. — Tfxhnological Aspects of thk G()I,d- 

 scHMiDT Reaction.' 



The technolo.i;ical importance of Goldschmidt's 

 reaction can hardly be over-estimated. The whole 

 subject is as yet in its infancy, but already it ma}- be 

 said to constitute a new branch of technologw to 

 which the name of " Aluinino-thermics " has been 

 given. 



In the first place, the reaction serves for the 

 preparation of a number of pure metals and allo}-s 

 of considerable value in the iron and steel and allied 

 industries. Of the former of these we mav mention 

 chromium (98-99% pure), manganese (96°;,). and 

 molxbdenum (98-99%). Chromium is used in the 

 manufacture of high-speed tool steel, as well as 

 armour [ilate : manganese is also used in the 

 manufacture of very hard steel. Amongst the allo\-s 

 we may mention chromium-manganese, manganese- 

 titanium, ferro-titanium. ferro-\anadium and ferro- 

 boron. CLT"' P '! 



251 



"Thermit"; containing a small amount of titanium 

 oxide is used in foundry %\ork. The mixture, jilaced 

 in a tin fastened to an iron rod (see Figure 2), is 

 plunged into the molten iron as s<xm as it is run from 

 the furnace into the ladle, and held at the bottom until 

 the reaction is over. The slag rises to the top and can 

 be removed. It is found that this treatment tends 

 to prevent blowholes and to give clean, dense 

 castings, the effect of the titanium being to increase 

 the fluidity of the metal and produce a finer grain ; 

 moreover, the sulphur content is decreased. 



In the slag from the reaction of chromium 

 '" thermit," minute rubies are found, ruby being 

 nothing but crystallised alumina coloured with 

 chromium : but they are too small to be of any 

 commercial value. A use, howe\er, for the slag has 

 been found. Dr. Buchner has discovered tliat, owing 

 to its comparati\-e freedom from metallic impurities 

 and absolutely anhydrous condition, it is preferable 

 t(> natural corundum (which it resembles) in the 

 manufacture of pottery, for which purpose it is 

 mixed with cla}- and burned, and is especialh- useful 

 tor making chemical apparatus which ma^• be 

 subjected to great changes in tiiuperature without 

 f r.irtiirni'' . 



I'IGURE 3. 



Aliimino-therniic repair to the stern frame of the 

 s. s. "Sexilla" after t\vel\e months. 



■■■ F. E. Weston and H. R. Ellis; "Thermic Reactions in Vacuo." Trntisactions of flic Faraday Society, (1910), Vol. VI. 



i The writer's heartiest thanks are due to "Thermit. Limited" for their kindness in supplying him with full 



information concerning the technological applications of Goldschmidt's Reaction, for opportunity to examine their 



apparatus and methods, and for the loan of the blocks of several illustrations in the present article. 



, '■ Thermit " is the registered name given to a mixture of aluminium and iron oxide. 



