4? On the Ufc of Calcareous Stones ht 



aiiJ filex is combined v/ith the iron {lone?, the lava will flow 

 from the furnace comparatively cold, tenacious, and of a. 

 brown or pale dirty green colour, containing iron : when 

 the mixture is jufl, the colour of" the fcoria is pure white, 

 enamelled with a variety of blue fliades, waving, circular, or 

 formed in llraight delicate lines, arifing from a peculiar ex- 

 ifting modification of a minute portion of the metal. Should 

 lime be added in excefs, the quality of the iron will not be 

 improved, but the quantity confiderably diminiflied. This 

 Iof< takes place in two ways; when the iron is oxygenated, 

 the prefencc of an extra quantity of fufed earths fiicilitatcs 

 the oxj-dation of the metal, whenever it comes into contafb 

 with atmofpheric air *. The flrong current of air from the 

 d'ifcharging pipe aRords ample opportunity for this oxyda- 

 tion; the fmall globules of metal deflagrate and become 

 combined with a great portion of oxygen ; the want of car- 

 bon in the furnace prevents any part of the oxygen from 

 being again removed ; the oxydated iron incorporates with 



• As I have frcqiicnt occafion to uTe tlic two ver'os, to oxygenate, aiul 

 tr, ox3'datc, I (hall expiifs the precife meaning I attach to two woids 

 which are foir.etiiTn,s indifcriininately ufed, and to which it has been 

 thought that M. Lavoifier had affixed no ftparate or diflinft meaning. 1 

 have uTed oxygenate to exprefs the progreiFive combination of oxygen with 

 tlic metal, without, b.ow^vcr, dettroyingits metallic fracture, or exhibitiag 

 iiiternaUy the finalleft appearance of an oxydc. Oxydation, on the other 

 h;ind, I have always uftd to exprefs the final confcquence of the combina- 

 tion of bxygen with iron, aiiJ the complete change from a metallic (tatt, 

 to that of a deta-rhed friable oxyde. For example, crude iron run fioni 

 the fcrnace, of a white frafture, is f.:id to be oxygenated. In cooling, 

 being expofcd to atmofpheric air, it acquires a confiderable quantity of 

 bluehli oxyde ; its lurfaee may then juftly be fald to be oxydated. It is 

 the fjme with malieable iron and fiecl; each of thefe fuller in quality from 

 the alTinirv oxvgtn has to combine with them, at a high temperature, 

 before the Icaft diminution of metallic frafture takes place; and in that 

 ftate I have always confidered them as oxyginated. When, however, 

 this was pad, and the combination of oxygen haddcftroycd every property 

 of metal, I have confidered this only as a flatc of oxydation. 



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