April 13, 1893] 



NATURE 



;6i 



of pure metal intermixed with carburised metal, and also 

 slag. The latter is said to play its part in rendering the 

 total mass more coherent when heated and worked. 

 This latter material when fused and cast into ingots is a 

 totally different material, and behaves somewhat like 

 steel. If this now comparatively homogeneous substance 

 contain enough carbon (which sometimes is not the case ; 

 in the latter instance it is brittle and redshort, behaving 

 somewhat like Bessemer blown metal) it works like a 

 soft steel. 



It follows, therefore,that if fusible compounds are present, 

 and evenly diffused throughout the pure metal, their effect 

 on steel is purely physical, and a heterogeneous metal 

 like steel may be compared with rocks, which are known 

 to be composed of siliceous particles, cemented or bound 

 together by other compound bodies. Dr. Sorbyslong ago 

 noted this, and drew attention to the comparative use- 

 lessness of ordinary chemical elementary analysis, simply 

 stating the percentage of elements present, and suggested 

 that proximate analyses were equally required. The 

 writer is fain to agree with him, his own experience of 

 the comparative failure of ordinary analysis as a trust- 

 worthy guide In the manufacture having been somewhat 

 extensive. The purest form of iron [known to the writer 

 is the Bessemer blown metal, beyond traces of carbon, 

 with less than ,\yth per cent, of sulphur and phosphorus. 

 It is pure iron (with some kinds of iron only traces of 

 these latter can be detected). This metal is worthless for 

 commercial purposes, and this is said to be due to the 

 presence of oxide of iron or possibly dissolved oxygen ab- 

 sorbed during the blow ; to a certain extent this has been 

 proved to be true. But the writer thinks that on the 

 whole the pure material, even when freed from oxygen, 

 would be commercially valueless, and if, shortly 

 speaking, the cement theory or mixture of bodies (the 

 one more fusible than the other), be true, pure iron is 

 unworkable. 



The opinions quoted are apparently not in accord with 

 the theory of solution previously summarised, and leave 

 unexplained the undoubted fact of the diffusion or solution 

 of carbon in iron at low temperatures, tending, of course, 

 if time be allowed, to the formation of a homogeneous 

 material. Yet a carbide of iron is known, " Fe4C," and 

 has been isolated. It appears to the author that one 

 somewhat reasonable explanation of this anomaly has 

 been afforded by W. Mattieu Williams. He compares 

 the union of carbon and iron to the processes of tinning 

 or galvanising. If a plate of copper is immersed in 

 melted tin a film of tin adheres to its surface, and if con- 

 tinued the tin will gradually soak into the copper, and in 

 time will go through. Tin or zinc penetrates iron in the 

 same way ; mercury also amalgamates with copper ; 

 therefore carbon (Fe4C) may be similarly distributed in 

 iron. 



This may or may not be the case, but in the author's 

 opinion it does not meet all the difficulties, or afford a 

 complete explanation of the phenomena taking place 

 when iron is heated and worked in contact with carbon. 

 Neither does the alternative theory of solution, either in 

 the ordinary sense of the word or, better, as defined by 

 modern physicists, afford a complete explanation. Yet on 

 the whole the latter seems to afford a better and more 

 complete all-round explanation of some curious changes 

 observable when steel is heated up to certain varying 

 temperatures, the results of which are now familiar 

 to us. 



Referring once again to the curious fact of the even 

 distribution of carbon throughout iron, when plates of 

 uneven composition as regards the percentage of carbon 

 are heated together, it appears as the outcome of recent 

 research' that chemical action, "or something closely 

 approximating to it," takes place between solids, and even 

 at low temperatures. Many experiments are given — thus 



1 William Hollock, American Journal of Science, vol. xxxvii. 1889. 



NO. 1224, VOL. 47] 



dry ice and rock salt unite when placed in contact at a 

 temperature decidedly below zero. 



This is a very old experiment, but it is interesting 

 as an example of the union of two solids below the fusing 

 point of either, but above that of the product. He ob- 

 tained similar results in other cases with sodium, potas- 

 sium, calcium, and ammonium chloride, &c. This 

 suggests the question. Are the metals combining to form 

 an alloy " in the new way," i.e. in the form of solids, a 

 freezing mixture ? 



Space does not admit of further quotation ; the fact 

 remains that solids combine with solids to form an alloy, 

 or possibly what is termed a chemical combination. 



At first sight this seems inconceivable and irrational. 

 Many alternative theories and explanations of these 

 curious phenomena are at our disposal. Yet there re- 

 mains one simple way of accounting, at least in some 

 degree, for this alloyage — or one ought perhaps to say the 

 interpenetration of one element into another, as with carbon 

 and iron. It is now, we think, generally admitted, in the 

 light of recent researches on the vaporisation of the ele- 

 ments, " both in vacuo and at ordinary pressures," that no 

 known element, however infusible, can be said to be 

 perfectly stable at any temperature when freely exposed 

 in space ; and it is extremely probable that even such sub- 

 stances as iron and carbon are slowly dissociating at 

 ordinary temperatures very much as water evaporates, 

 and it follows that these are always enveloped in a thin 

 atmosphere of their own vapour. The quantity of 

 matter present in this form may never be recognisable ; 

 it may indeed be beyond the limit of our senses. Yet if 

 such a process takes place, it affords a probable 

 explanation of the diffusion of solids into each other. 

 For admitting this it is evident that any mass or mixed 

 masses of matter exist in an atmosphere formed by them- 

 selves. Such masses of matter cannot be discontinuous, 

 strictly speaking, the sensible particles of which they 

 are composed are not completely isolated from each 

 other, and from this point of view the conception of the 

 interpenetration of iron by carbon, or indeed other 

 bodies, is, one thinks, rendered more easy. 



John Parry. 



NOTES. 



Botanists all over the world will be sorry to hear of the 

 death of the famous Swiss botanist, Alphonse de Candolle. 

 He was in his eighty-seventh year. We hope to give on a future 

 occasion some account of his services to science. 



We regret to hear, through the Botanical Gazette, of the 

 death of the Rev. T. Wolle.ipastor of the Moravian Church, 

 Bethlehem, Pennsylvania, an ardent student of freshwater 

 algae. 'Of his three most important publications, "Freshwater 

 Algae of the United States," " Desmids of the United States," 

 and *' Diatoms of the United States," at least the first two will 

 always be standard works in the subject of which they treat. 



The ordinary general meeting of the Institution of Mechanical 

 Engineers will be held on Thursday evening and Friday evening, 

 April 21 and 22, at 25, Great George Street, Westminster. The 

 chair will be taken at half past seven p.m. on each evening by 

 the president, Dr. William Anderson, F.R.S. The following 

 papers will be read and discussed, as far as time permits : — 

 Second report to the Alloys Research Committee, by Prof. W. 

 C. Roberts- Austen, F.R.S. (Thursday, and discussion possibly 

 continued on Friday) ; tensile tests and chemical analyses of 

 copper plates from fire-boxes of locomotives on the Great 

 Western Railway, by Mr. William Dean (in connection wilh the 

 above report) ; Research Committee on marine-engine trials : 

 abstracts of results of experiments on six steamers, and con- 

 clusions drawn therefrom in regard to the efficiency of marine 

 boilers and engines, by Prof. T. Hudson Beare. The anniver- 

 sary dinner will take place on Wednesdayevening, April 19. 



