TRANSACTIONS OF SECTION B. 61 i 



them with that of the Bessemer flame, led to the conclusion that it was not the 

 spectrum of carbon in any form, or of manaranese, but that of manganic oxide. 



The spectrum is a complex one, which exhibits differences in constitution 

 during different periods of the ' blow,' and even during different intervals in the 

 same period. As originally observed by Watts, the spectrum differs in different 

 works, the difference being due to temperature and to the composition of the 

 metal blown. 



During the First Period. — The lines of the alkali metals, sodium, potassium, 

 and lithium, are seen unreversed on a bright, continuous spectrum caused by 

 carbon monoxide. The C line of hydrogen, and apparently the F line, were seen 

 reversed during a snowstorm, when much moisture entered the metal with the 

 blast. 



During the Second Period, the ' Boil.' — Bands of manganese are prominent, 

 overlying the continuous spectrum of carbon monoxide. There are lines of carbon 

 monoxide, manganese, and iron, also those of the alkaline metals. 



During the Third Period, the ' Fining Stage.' — The spectrum is the same as the 

 foregoing, but the lines of iron are not so strong and not quite so well defined. 

 Some of the short lines of iron disappear; the lines of the alkali metals are 

 visible. 



The alkali metals do not show themselves in the Bessemer flame until a layer 

 of slag has been formed and the temperature has risen sufliciently high for these 

 basic constituents to be vaporised. At the temperature of the ' boil,' or second 

 period, both metallic manganese and iron are freely vaporised in a current of 

 carbon monoxide which rushes out of the bath of molten metal. The evidence of 

 this is the large number of bands of manganese and lines of iron in the spectrum. 



When the metal blown contains but little manganese, the manganese spectrum 

 in the flame does not arise from that substance being contained in the bath of 

 metal ; it must be vaporised from the slag. That this is so has been proved by 

 photographs of the spectrum from samples of slag obtained from the Crewe works. 

 This explains the fact observed by Brunner, namely, that when a converter is 

 being heated with coke after it has been used, but not relined, the spectrum of the 

 Bessemer flame makes its appearance ; manifestly it comes from the adhering slag. 



The luminosity of the flame during the ' boil ' is due, not merely to the com- 

 bustion of highly heated carbonic oxide, but also to the presence of the vapours of 

 iron and manganese in the gas. 



The disappearance of the manganese spectrum at the end of the ' fining stage,' 

 or third period, is primarily due to a reduction in the quantity of the heated 

 carbon mono.xide escaping from the converter, which arises from the diminished 

 quantity of carbon in the metal. When the last traces of carbon are gone, so that 

 air may escape tlirougli the metal, the blast instantly oxidises any manganese 

 either in the metal or in the atmosphere of the converter, and furthermore oxidises 

 some of the iron. The temperature must then fall with great rapidity. 



The entire spectroscopic phenomena of the ' blow ' are undoubtedly determined 

 by the chemical composition of the molten iron, and of the gases and metallic 

 vapours within the converter, the temperature of the metal, and that of the 

 issuing gases. 



The Temperature of the Besiemer Flame. — Tlie probable temperature of the 

 Bessemer flame at the finish is that produced by the combustion in cold air of 

 carbonic oxide heated to about 1,580° C. — that is to say, to the temperature which, 

 according to Le Ohatelier,' is that of the bath of molten metal from which the gas 

 has proceeded. 



5. On the Chemistry of Coal Formation. 

 By J. W. Thomas, F.I.C, F.C.S. 



The age of the coal, and the physical conditions, such as the effect of water, 

 heat, and pressure, should throw light upon the chemistry of coal formation ; but 



• Comptes Mendus, vol. cxiv. 



B B 2 



