Hot air blast

348 Progress el Practical g) Tlzeoretlcal aIechanlcs ~ C/~emislu/" of an atom ofsulphuric ether~ and an atom e r a new acid which we propose to designate (znanthic acid, and which is tbrmed of C ~• }I a6 0 ~, T h e condensation of its vapour is that of formic and acetic ethers. T h e oil pre~ents itself under tim farm of a greasy oil which crystallizes at 5(; ° Fahr. In its free st;tie it contains one atom of water, which it loses by distillati,~n, ]}y combining it with sulphurie ether, we can easily reproduce (~nanthic ether. W e have deemed it necessary, for the purpose of establishing the compo_ sition of one of the most remarkable of these acids, vi'/,, the mellgic acid, to make some analytic invesligalions concerning its corr~bination wilb oxide of silver. We believe that this acid may be regarded as a hwlrous acid, and our experiments on Ibis point confirm the views of M. Dulong respecting oxalic acid. 'l?he m e l i t a l e o f s i l v e r d r i e d in vacuo, b y t h e side ofsulphuric acid, contains :mum hydrogen, which it loses only at tile temperature of 356 ° F a t m under t h e t b r m o f ~ a t e r ~ and with change of relent. T l . ~ r e i s not one other salt of silver which exhibits the same result; all tbe others are anhydrous. In Ibis particular instance, the formation of water appears to he the consequence of the reduction of tile oxide, and not a simple volatilization of water which had pre-existed in the salt. According to all known analyses, the melitic acid contain three atoms of oxygen. We have reason to think it contains 1bur, and besides two atoms ot" hydrogen; and that ibis hydrogen enters inlo the constitution of all the melitates except inlo that of silver heated to ~'5(i°, so t h a t this last represents a combination of metadlic silvei'~ with the radicle of hydrous acid. ~ E,I. New t'hiios,am,r.

Ilot ./lir Blast. T h e henefitswhich this new process appeared to promise, and the sanguine expectation~ of economy and profit that have been entertained, do not appear to be fully realized. Still it is not without its advantages; and with respect to the use of anthracite coal in the reduction of iron ore, tile application of the hot blast has evidently afforded, under the management of Mr. Cran% in Wales, the most encouraging indications of a success, which in its application to our own mines of coal and iron may prove of incaluable imlmrtance. T h e tbllowigg extracts from a communication of W. Wood to the London Mining dournal~ point out what he deems to be the causes of t~ilure in the use of hot air in the smelting" of iron, and also the incidental benefits which i t a h ' e a d y produces. It is much in be desired that experimenters and iron masters may not be too soon discouraged by the untavourable nature of these statements, tbr it is very possible that the means may be hit upon0f obviating the causes which appear In occasion a deterioration of the quality of the iron, and still secure to the hot air process all the facilities and ad. vantages to which both science and thct most evidently give it a claim. G. T h e use of heated air in smelting, leas greatly fi~cilitated the production of g r e y h'o% and has, in many instances, occasioned a material increase in the make; bat that it has been productive of the g r e a t advantages which w e r e at first supposed to accrue from its use, has been by no means established. I do not mean to dispute, that at some concerns, a reduction in the quantity of fuel made use of may have been effected, but that this has been the general result, I believe I may safely say~ is by no means the case; on the contrary, in the majority of the works w h e r e it has been made use o1; the savi~g ell'coted is a mere b a g a t e l l e ~ t h e aggregate cluantity consumed

Hot ~ i r Blast.

349

in smelting, and healing tile air, being very nearly equal to that which had been previously used in smelting with cold.blast. ~rom all I can collect from different parties who have adopted the system~ the only advantage they derive from it is, that tile furnaces work more unitormly, not being liable to the fluctuations which are experienced when cold-blast is made use of T h i s is undoubtedly an adwmtage of considerable importance9 and would be sutIicient to recommend its universal adoption~ were there no disadvantages connectcd with its use. which more than balance all the benefits derived from it~ and must permanently operate against its general introduction. \Vhat 1 allude tois~ the reduction of the actual strength of the iron produced by this process. T h a t this is a fac!, is now established beyond a doubt, by numetous experiments by different parties. I sometime ago institut(~d a series of experiments myselt~ on the relative strength of iron produced by the old and new t)roces~. T h e bars I made use of were one and one-eighth squar% and supported at each c n d o n supports two feet distant from each other; from th,~ centre 1 suspended a scale board~on which weights were placed, and increased seven pounds at a time~ until they broke, The bars were obtained from a neighbouring" iron works~ and were produced from the same material~, one ~et from cold-blast~ and the other from hot, and were to all appeara,~ce of preci.cely tile same quality, so much so thai there was not the lc~:t apparent differonce in the quality of each o:l inspecting tbe several fl'acturcs. '1'be averaged result was, that the coldblast iron broke ureter a weight ot'200.9 Ibs.~ and ti~e hot-blast iron under a weight of 1568 lbs. This shows a (leiicielacy of more than twenty per cent. in the strength of the hot-I)h~t. T h e deflection under equal weights was rather in favourof" the hot-blast iron, proving it to be less flexible until it arrived at the breaking point. This is a most serious objection to such iron, and operates against its safety, when applied to purposes requiring great strengtla. I have never seen any satisfactory reason assigned for the deficiency which is evident in its strength; it, however, in my opinion, admits of a solution on cicero!eel principles. Sir Humphrey Davy was the first person who established the probability of the different earths being" oxydes of metals~ reducible to the metallic state in tile same manner as the ores of other me. tel-:; :rod lJerzeli~3s succeeded in forming" an :alloy ofsiliciom and iron~ thereby es .... ~hmg the fact of'their affinity tbr each other. That the earth~., in combination with tile ironstone and other materials made use of in the blast furnace~ are in small proportions reduced along with the oxyde ofiron~ there cannot be a reasonable (loubt~ and is in a measure l)roved by the analysis of pig-iron~ which is invariably found in combinatiou ~vilh alumine~ lime~ and silex, in various proportions. These there is every reason to believe, are in combination with ti~e iron in a metallic slat% thereby forming an alloy~ whose ibrce of cohesion is much less than that of pure iron~ and in proportion to the quantities o f t h e s e e a r t h s revived will its strength be affected. 1 am the more confirmed in this opinion by the result of an analysis which 1 made some years ago of iron produced fl'om ironstone and from refinery cinder~ the !briner producing much stronger iron than the latter. This atmlysis showed that there were three pet' cent. of earthy matter in the stronger iron or that t)roduced from ironstone, and five per cent. in the weaker or that produced from refinery cinder. Both samples were smelted at the same iron works, with the same coal and limestoue~ and under precisely similar cir,~umstances, therelbre the fair inference to be drawn from the analysis is~ that the earthy matter~ in a metallic slat% was the primary cause of the deVoL. X X . - - N o . 5.~OVr;~lBl~lb 1857. $0 I

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Progress of Practical ~ Theoretical Mechanics ~. Chemistry.

fieieney ia the strength, T h e predominant earth in each case wassilex, from which we may infer that this earth has a weaker affinity for oxygen than alumioe and lime~ and is consequently more readily reduced to the metallic state than either of the others. That the affinity of silex for iron is strong, is proved by the circumstance that the refining processes made use of to produce malleable iron~ do not entirely remove it, for it is found in the finished bar~ in quantities bearing a proportion to that found in pigiron, although of course in smaller quantity. By the old process, the temperature of the furnace is much reduced by the introduction of the immense quantityof cold-air required to carry on combustion, and which must necessarily abstract a great quantity of caloric to elevate it in the temperature of the mass of matter in the furnace, and that, in the vicinity of the twyers, where intense heat is most required, foe the purpose of producing perfect fusion of the earthy part of the materials, to effect a thorough separation of the metal from them. By the new pro. cess of heating the air previous to its introduclion, its refrigerating effect is, in a great measure obvialed~ tim temperature is kept up~ a.r_,d 1)reserved in that state best calculated to increase the affinities of the oxygen in the ore.. and of the iron when reduced to a metallic siale~ for the carbonaceous matter with which it is in contact, thereby facilitating the combination of a larger portion of carbon with the iron than is efi'ected with cold-blast. I[ the tiwnaee, by this process, is kept in a state better adapted to reduce the oxyde ofiron~ it also stands in the same position as regards the earths, and there cannot be areasonabledoul)tas to the fact of their being revived in l a r g e r proportion than nnder the cold-blast system; and to this cause, I am persuaded, is to be attributed the deterioration in the quality as fi~r as its strength is concerned. To satisty myself on this point as far as possible, l analysed theiron~ the exf)eriment on the strength of which l have hetbre noted~ the result of which goes far to confirm this opinion, and is as follows: : From 100 l,a~ts of cold-blast iron 1 obtained Silex 2,33 or Silicinm 1.165 Alum)he 0.78 or Aluminum 545 Lime 0,26 or Calcium i86

Silex Alumine' Lime

3.37 And from 100 ][)arts of hot-blast iron 4.27 or Sit)alum 1.10 or Aluminum 0.41 or Calcium

1.896

,

2.135 0.767 0.399

5.78 3.30t These analyses correspond very nearly with those before mentioned, and, in my opinion, leave little doubt as to the inferior quality of the iron produced with hot-blast being attributable In the same cause as that which operates against that produced from refinery cinder, which has hitherto baffled every attempt to improve its quality. The cinder here alluded to, is that produced in the first proees%made use of" in converting cast inlo malleable iron, which is technically termed~ refining. That produced in the subsequent peocesses, makes iron of a much better quality, and in many cases a judicious mixture of it~ improves the quality of that produced from ironstone. I have not had an opportunity of fairly trying the effect of" hot-blast on the strength ot malleable iron~ on a sufficiently extensive scale to speak decidedly

Iron T~'ade in ~qcotland.

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of it from my own knowledge, but from intormation I have received, from a person of good practical knowledge, and recently employed as a super. intendant over a part of the mann~hctoring departmen t o t an extensive iron works, where the princifde is applied to one filrnaee, I have every reason to believe that the effect is equally injurious to bars as to east-iron; at any rate, as far as regards the iron produced at this particular works, and where that produced with cold blast is generally good. What this person states i8, that the iron produced there is excessively weak and coldshort, so much so that a very small proportion of it can be made use of, mixed with the other iron. This is precisely the character of refinery cinder iron, to which it is in most respects analogous. Circumstances may probably operate in some situations to modify the character ofit~ but whether sufficiently to make it desirable to adopt it, is what 1 am not at present prepared to speak to, experience alone can decide this point. I am, Sir, your obedient servant, ~bers~chan Iron [Forks, Pont~pool, W. WooD. ,~lug. 57 183"/. Min../our.

Iron Trade in Jtcotland. It appears from a statement of Bald and Geddes, mining engineers,/hat it is about seventy years since iron-wo,'ks were erected in Scotland, at Carron, in Stirliugsbire~ and for twenty years afterwards, the annual pro. duce of pig-iron there, was under 8000 tons. In lorry years after Carron Works were in operation, or about 1805, seven additional iron-works appear' to have been built~ and about this period the yearly make of iron in Scotland might be about 24,000 tons. Only one more iron-work appears to have been built in the succeeding twenty years; and, in 1825, we tind the annual produce of iron increased to 29,~200 ton% the number of furnaces then built being twenty-five, of which only seventeen were in blast. At the beginning of tile current year~ there were thirty-seven furnaees at work, producing at the rate of 99~500 tons of pig-iron annually, being an increase of twelve furnaces in twelve years, and an additional yearly make of iron of 69,000 tons, compared with 18~5. Besides this increased num. ber of furnaces in operation in 1837, there were five additional furnaces in progress of buihllng, and four more contemplated, which, when completed, will produce ~7~000 tons more iron yearly; the annual make of iron in Scotland~ would thus be 1~6,500 tons, or about one-sixth part o[ the gross estimated make of iron in Great Britain yearly. In 1825, Scotland only produced about one-twentietlt part of the make of iron in the United Kingdom. This extraordinary increase in the iron trade of our country is principally found to have taken place in the county of Lanark, and the apparent p h y •tcal causes which have contc bored to t ~e recent rap~d extenston of thts trade in the Lower Ward of that county, may be considered as threefold. 1st. The moderate depth to, and thickness of, the seams of coal, which enables them to be readily and cheaply produced. 9~d. The abundant supply of what is locally caLted blackband ironstone, which, being of a I~ituminous nature, is easily calcined; and ..qdly, the late discovery, and now general application at the iron-works of that county, ot Neilson's hot blast, which has produced great economy in the quantity of c0al requisite to produce good pig-iron; this improved mode of blast is also applied at all the'other iron-works of Scotland. This blackband ironstone S

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