262 



NA TURt 



[July 12, 1S94 



carbon (Roscoe) or to carbon monoxide (Lielegg and Kupel- 

 wieser), but to manganese and other elements in the pig iron. 



The very careful examination of these spectra by Watts and 

 his comparison of them with that of the Bessemer flame led to 

 the conclusion that it was not the spectrum of carbon in any 

 form nor of manganese, but that of manqanic oxide. 



Owing to (he courtesy of Mr. F. W. Webb, the engineer of 

 the Locomotive Department of the London and North- Western 

 Railway, and of Mr. E. P. Martin, the manager of the Dowlais 

 Ironworks, observations have been made at Crewe and at 

 Dowlais during the past year. Ninety spectra were photographed, 

 about fifty of which were available for study. 



Ninety-two lines were identified with lines in the solar 

 spectrum, with lines in Kayser and Runge's map of the arc 

 spectrum of iron, and in spectra from steel and ferric oxide 

 heated in the oxyhydrogen flame. 



The Constitution of the Bessemer Specti-um. 



The spectrum is a complex one which exhibits differences in 

 constitution during different periods of the "blow," and even 

 during diflTerent 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. 



. The lines of the alkali metals, sodium, 



potassium and lithium, are seen unreversed on 



During the a bright continuous spectrum caused by carbon 



first period. monoxide. The C line of hydrogen and ap- 



I parently the F line were seen reversed during 



I a snowstorm. 



Bands of manganese are prominent, over- 

 Daring the lying the continuous spectrum of carbon mon- 

 second period. oxide. There are lines of carbon monoxide, 

 The "boil." manganese, and iron, also those of the alkali 

 metals. 



stage. 



visible. 



^ . f The spectnim is thesame as the foregoing, 



IJuring j j^yj j|^^ \\a^% of iron are not so strong and not 



Th '^Mi'Tnc qu''e so well defined. Some of the short lines 



' ,, " disappear. The lines of the alkali metals are 



The alkali metals do not show themselves in the Bessemer 

 flame until a layer of slag has been formed, and the temperature 

 has risen sufficiently high for these basic constituents to be 

 vapourised. At the temperature of the " boil " or second period, 

 both metallic manganese and iron are freely vapourised in a 

 current of carbon monoxide, which, in a highly heated stale, 

 fu-hes out of the bath of mollen 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 man- 

 ganese spectrum in the flame does not arise from that substance 

 being contained in the bath of metal, it must be vapourised 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 (act observed by Hrunner, namely, that when a 

 converter is being heated with coke after it has been used, but 

 notrelined, the spectra of the Bessemer (lame makes its appear- 

 ance i manifestly it comes from the adhering slag. 



The luminosity of the flame during the "boil" is due, not 

 merely to the combustion of highly heated carbonic oxide, but 

 also to the presence of the vapours of iron and manganese in the 

 gai. 



The disappearance of the manganese spectrum at the end of 

 the "fining stage," or third period, is primarily due to a re- 

 duction in the quantity of heated carbon monoxide escaping 

 from the converter, which arises from the diminished quantity 

 of carbon in the metal. When the last traces of carbon arc 

 gone, to that air may escape through the metal, the blast 

 instantly oxidise* any mnnganeie, either in the metal or in the 

 atmotphere of i' r, and, furthermore, oxidises some of 



the iron. The must then fall with grea' rapidity. 



The entire s| .-^..-.-piiit phenomena of the " blow " are un- 

 doubtedly determineil by the chemical composition of the 

 molten iron, and of the gases and metallic vapours within the 

 converter, the tempera'.ure of the metal and that of the issuing 

 gasei. 



Tilt Ttmferaliirt of the Bemmer I'lamt. 



The probable temperature of the Bessemer flame at the 

 finish is that produced by the combustion in cold air of carbonic 



NO. 1289, VOL. 50] 



oxide heated to about is8o°C., that is to say, to the tempera- 

 ture which, according to Le Chatelier (Cc//;//« Rendu:, vol. cxiv. 

 p. 670) is that of the bath of molten metal from which the gas 

 has proceeded. The bath of metal acts simultaneously as a 

 means of heating the blast, producing the gas, and as a furnace, 

 on the regenerative principle, which heats the gas prior to its 

 combustion. The heating effect is therefore cumulative. The 

 temperature, as is well known, can easily rise too rapidly, and 

 the metal has then to be cooled. 



If we may judge by the lines and bands belonging to iron and 

 manganese which have been measured in photographed spectra 

 of the Bessemer llame, the temperature must nearly approach 

 that of the oxyhydrogen tUme, and may easily attain the melting 

 point of platinum, namely, 1775^ C. (Violle). 



From thermo-chemical data the heat evolved during the 

 " blow " has been calculated, but the specific heats of cast iron, 

 slag, carbon monoxide, and nitrogen are unknown at tempera- 

 tures between 1200° C. and 2000° C. If we allow for 50 per 

 cent, of heat developed at high temperatures being lost by 

 radiation or otherwise, then the estimated temperature of the 

 metal in the converter is more than 1900 C. 



Le Cbatelier (Comf-tes Ketidus, vol. cxiv. p. 670) found the 

 steel in the ladle of a Robert converter to be at 1640° C, 

 Reasons are adduced for believing that it was hotter than this 

 at the highest temperature of the " blow." 



The Tet-hni^al Asped of this Investigalum. 



The complete termination of the "fining stage" is cleaily 

 indicated, but there is no indic.ition by the llame of the compo- 

 sition of the metal within the converter at any previous stajjc. 

 As the progress of the " blow " is governed by the composition 

 of the metal and its temperature in the converter, and as these 

 cannot be controlled with perfect exactitude during each " blow," 

 it follows that the practice of complete decarburisalion ' is the 

 best course to pursue, the required amount of carbon and man- 

 ganese being added subsequently in the forms of grey iron, 

 Spiegel, or ferro-manganese. 



Mathematical Society, June 14. — Mr. A. B. Kempe, 

 F R. S., President, in the chair. — Abstracts of the following 

 communications were read by the secretary (Mr. R. Tucker). — 



The solutions of sinh (aj- \y =/(>)i coshi A - W =_/(.>), Xa 



constant, by Mr. F. H. Jackson. — .\ theorem in inequalities, 

 by Mr. A. R. Johnson. This was a theorem which in a natural 

 way fills up the gap between the .^.M. and the G.M- of a 

 number of positive quantities. — Some properties of a circle, by 

 Mr. R. Tucker. — Note on four special circles of inversion of a 

 system of " generalised Brocard " circles of a plane triangle, by 

 Mr. J. Griffiths. — On the order of the tliminanl of two or more 

 equations, by Dr. K. Lachlan. In analytical work it is often 

 important to know what will be the order of the eliminant of 

 two equations containing several variables when one of them Is 

 eliminated. This question can in general be answered even 

 when it is not easy to perform the elimination. A discussion 

 of the question is given in Serret's " Cours d'Algihre Supt'ri- 

 eure," and is said to be due to Minding. But a simpler method 

 would seem to be arrived at by geometrical considerations. 

 Thus, suppose that it is required to find the order of the elimi- 

 nant in^ when x is eliminated from any two equations, 



/i(-'', J') = o and/„(.r, y) = o. 

 Let a third variable, =, be introduced, so that the equ.ations 

 may be written in the homogeneous forms, 



'»'i( >i.>'i -) = o and <()j(.v, j; z) = o, 

 and let the degrees of these equations be m and «. When these , 

 equations arc regarded as representing curves, the eliminant 

 will represent the lines connecting the point,]' = 0, c -= o to 

 the points common to the two curves. Hence, the order of the 

 eliminant will be at most inn, becau-e the curves will intersect 

 in that number of points. But a little consideration will show 

 that it will not in general be necessary to take into account the 

 points common to the two curves which lie on the lines i' = o, 

 : = o. Similarly, if it is requlre^ to eliminate i and j' from 

 three equations containing.!,,)', and ;, let a fourth variable, «'. 

 be introduced, so as to make the equations homogeneous. Then 



' The word". " carbiirisinK " .ind * dec.irburising '" arc to be preferred ' 

 "carbonisintE " and " decartioniftiriK " wtien applied to mctaJK, beciuse thr ■ 

 expression* were Ihoic oriftinally used in the (dder works r.n niclallurjjy, ai. 

 Ihcy avoid confusion with tnc other signilicaiionof the Wjrd "c.irboniiinc- 



i 



