VOL. LXXXV.] PHILOSOPHICAL TRANSACTIONS. 587 



the apex of the cone of the filtre by the solution of iron. The quantity of 

 black matter on the filtres from the 2 former solutions was apparently 6 or 8 

 times more than from the solution of iron: but it adhered too firmly, and was in 

 too small a quantity, to determine the proportion accurately by weight. I esti- 

 mated the quantity of the black, matter to be one per cent, of the steel and wootz, 

 and a proportionally smaller quantity from the iron. On account of the very 

 black and turbid appearance during the dissolution of wootz and steel, I was 

 much surprized by the smallness of the quantity of black matter on the filtres; 

 nor could I by experiment find that any of it passed through the filtres with the 

 solutions. 



This black matter being sprinkled on boiling nitre, a deflagration took place, 

 and a large proportion of residue was found, and ascertained to be oxide of iron. 

 The black matter was therefore a compound of iron and carbon, or, as some 

 chemists term it, plumbago; and which in the new system is denominated a car- 

 buret of iron. I estimate the quantity of carbon in wootz and steel to be nearly 

 equal; and that quantity to be about -^ of a 100th part, or -gJ-g of the weight of 

 these 2 substances. 



I am in the next place to give an account of the solutions just mentioned of 

 wootz, steel, and iron. On standing, it has been observed, there was a de- 

 position of white matter, and formation of green crystals in a liquid. The 

 liquid being decanted, was examined, and found to be sulfate of iron and super- 

 abundant diluted sulphuric acid. The green crystals were obviously those of 

 sulfate of iron. The white matter I supposed was the siderite of Bergman; 

 which is now believed to be phosphate of iron. I made many experiments to 

 ascertain its nature, but it is only necessary to state, that it readily dissolved in 

 hot water ; and the solution afforded nothing but crystals of sulfate of iron. 

 These crystals, by dissolving in a little water, and by boiling to leave behind 

 water insufficient for crystallization, yielded on cooling a white sediment as 

 before. This white matter yielded colcothar, a red oxide of iron, by applying 

 the flame with the blow-pipe. The white matter therefore was not siderite but 

 sulfate of iron, which could not crystallize on account of deficiency of water. 



§ 7- Experiments with oxide of wootz, steel, andiron. — 1 200 grs, of wootz 

 dissolved by diluted sulphuric acid, and then precipitated from this acid by pot- 

 ash, yielded greenish oxide; which on drying in a stove became a reddish-brown 

 light powder, weighing 2700 grs.; and by ignition it was reduced to 2000 grs.; 

 300 grs. of this oxide were made into a paste with linseed oil; which, being 

 wrapped in paper, was put into a crucible and exposed for near an hour to a 

 fierce fire in the wind furnace. On cooling, a cake of metal weighing 200 grs. 

 was obtained, which had the essential properties of steel. The pyrometer de- 



4 F 2 



