NOTICES OF BOOKS. Spark Spectra of the Metals. By CHARLES E. GISSING, F.R.G.S., Member of the Society of Arts, Rear-Admiral R.N. (retired). London: Baillière, Tindall, and Cox. THIS Collection of fifty photographic spark-spectra has been prepared by the author, using a dense glass prism spectrograph by Hilger and Wratten's panchromatic plates; they are limited to the visible portion of the spectrum from A3888 and 17724, and an accuracy of 1 Angoström unit is claimed. There is a short introduction dealing with the details of the spectrograph and the coil, the arrangement and manipulation of the secondary battery, &c. Reproductions of the spectra of forty-four elements are given, including hydrogen and helium; and six alloys, and brass, German silver, magnalium, type metal, and gold and silver coins, and a brief description is given of each experiment. The reproductions are by the half-tone process. Unfortunately no attempt has been made to eliminate the air-lines, and the spectra are therefore complicated. A scale of wave-lengths is printed at the bottom of each some distance below the lines, but it is by no means accurate, some of the divisions being twice the width of the adjacent ones; they are evidently ruled by hand. For these reasons the scale is practically useless, and although an accuracy of one unit is claimed, it would be found exceedingly difficult to determine the wavelengths of the lines shown with any approach to that precision. On the whole, the practical utility of the atlas is very limited, but its appearance is to be welcomed as showing that the preparation of photographed spectra no longer presents any great difficulty, and that the usefulness of the spectroscope as an aid to research is becoming generally recognised. Practical Sanitation. By GEORGE REID, M.D., D.P.H. With an Appendix on Sanitary Law by HERBERT MANLEY, M.A. Cantab., M.B., D.P.H. Fifteenth Edition. London: Charles Griffin and Company, Ltd. 1910. THE last edition of this work was issued so recently, and gave such a complete account of the principles and practice of sanitation, that the new edition has required very little revision. The most important additions in it relate to the ventilation and warming of school buildings. The author is a strenuous advocate of modern theories on this question, and lays special stress on the defects in the older methods of providing for ventilation in schools. Full accounts are given of the tests he has carried out in buildings of the modern Staffordshire type, and the results provide a striking argument against the old form with a central hall. In matters of detail the new edition has undergone some slight alteration, and statistics have been brought down to the latest possible date. Oil. By C. AINSWORTH MITCHELL. London, Bath, and New York: Sir Isaac Pitman and Sons, Ltd. THIS small book gives a popular account of the nature, origin, properties, and uses of all substances which are included under the name "oil," i.e., animal, vegetable, essential, and mineral oils. The information is in all cases well chosen, only typical products being treated, and these are discussed in outline only. The illustrations of such subjects as cutting lavender, peppermint harvest, &c., are no doubt inserted for the benefit of the general reader, who will find the book sufficiently lightly written to provide pleasant reading which is at the same time instructive, while the merchant or business man will be able to gather from it, at any rate, as much as he is likely to remember about the oils, and the titles of works which he will find valuable for further reference are mentioned in the preface. Sept. 2, 1910 Fertilisers for Wheat Soils. By MILTON WHITNEY. Washington: Government Printing Office. 1910. THIS bulletin gives a summary of the results of the fertiliser tests on wheat soils which have been carried out at the different experiment stations attached to the United States Bureau of Agriculture. The tests, which have been continued over long periods of time, both in America, at the Chio and Pennsylvania stations, and in England at Rothamsted, are also included, and, finally, the general conclusions to be drawn from the results obtained are discussed. It is found that the chances of increased production are greater when mixtures of two or three fertilisers are applied than when only a single substance is used, but on an average the increased value of the crop does not exceed the cost of the fertiliser. Small applications of one fertiliser appear to yield as good an increase as larger amounts, and there seems to be no evidence of a cumulative effect of long continued applications. MISCELLANEOUS. Solubility of Insoluble Silver Salts.-G. Stafford Whitby. The author publishes results of the determination of the solubility of silver chloride, chromate, oxide, and other salts obtained by the direct chemical method. These results agree very well with those obtained by the conductivity method.-Zeit. Anorg. Chemie, 1910, lxvii., No. I. Brussels Exhibition.-As it has only been found possible to allot space in the Chemical Court of the reconstituted British Section of the Brussels Exhibition to little more than half of the original exhibitors, Sir Boverton Redwood, Chairman of the Chemical Industries Committee, has addressed the following letter to the remaining firms, and it is hoped that this novel suggestion will be unanimously adopted :: "GENTLEMEN,-The response to the circular-letter of the Director of the Exhibitions Branch of the Board of Trade, dated August 18th, has been so prompt and generous that considerable difficulty has been experienced in allocating space to all those who have expressed their willingness to exhibit in the reduced area available for the reconstitution of the British Section, and no further applications for show cases can be considered. In view, however, of the high appreciation which the exceptionally meritorious exhibits illustrating the British Chemical Industries met with at the hands of the International Jury, I am sure that it will be the unanimous wish that there should be, during the remainder of the period for which the Exhibition will remain open, some record of those exhibits which cannot be replaced, and, as Chairman of the Chemical Industries Committee, I beg that you will furnish a descriptive account of your exhibit, with photographs if possible, which can be exhibited in a suitable frame on a wall space which has been appropriated for the purpose. It is suggested that a convenient size for such a frame would be four feet by three feet, but in exceptional circumstances it is hoped that it may be found possible to find space for a larger frame. As the new British Section is to be formally opened on September 15th, I trust that you will kindly give this matter your immediate attention and let me hear from you as soon as possible. I would add that frames of the dimensions indicated above will be supplied free of cost by the Exhibitions Branch of the Board of Trade, to whom your photographs should be forwarded at the earliest possible date.- Yours faithfully, BOVERTON REDWOOD, Chairman of the Chemical Industries Committee." IT was with considerable diffidence that I accepted the position of President of this section. The long list of illustrious and eminent chemists who have occupied the Chair in the past, scientists of the highest attainments, and usually professors of our educational institutions, is indicative of the very high standard to be followed. As, however, it was urged that a President with experience in the metallurgy of iron and steel was desired, I bowed to the decision of the Council, concluding that even as a mere layman I might, in this Address, discuss one or more subjects to which prominent metallurgists have for the past thirty years directed their earnest attention, both in Europe and America. I refer to some of the underlying phenomena connected with the effect of sulphur and silicon on the carbon condition of commercial cast-iron. The effect of sulphur and silicon on cast-iron has received the attention of Karsten, Percy, Weston, Howe, Keep, West, Dillner, Bachman, Summershach, Wüst, Johnson, Stoughton, Hailstone, Longmuir, Adamson, Turner and Schuler, Levy, and many others. They all agree in concluding that sulphur tends to make iron white by retaining the carbon in the combined state, and that silicon tends in the opposite direction. Professor Howe and Dr. Wüst have endeavoured to arrive at the exact quantitative effect of sulphur and silicon in preventing or facilitating the decomposition of the carbides. Howe recognised that the data available are insufficient on which to make any final conclusion. Wüst found, by a series of trials, that in pigs containing 3'15 per cent carbon and about 1 per cent silicon, on an average o'or per cent sulphur prevented the separation of 0.02 per cent graphite, but that with 2 per cent silicon its effect was much less. It is the general experience, that the effect of sulphur depends on the proportion, not only of silicon, but of the total carbon and manganese, and of the temperature at which the iron is cast, and the size and temperature of the mould into which the metal is run. Under some critical conditions o'i per cent sulphur may prevent the separation of 3 per cent graphite. Howe's discovery-that the tendency of silicon, in increasing the decomposition of the carbides, is rapid at first, especially as the silicon rises from zero to o 75 per cent, and then slower and slower with each further increase -is very important; so also is the generalisation of Messrs. Charpy and Grenet-that the separation of graphite on annealing iron which is initially white, containing the whole of the carbon in the combined condition, begins at a temperature which is the lower the greater the percentage of the associated silicon, and that the separation of graphite, once begun, continues at even lower temperatures than that at which it started. The evidence advanced by Phillips, Prost, Campredon, Schulte, and others-that, on dissolving sulphurous irons in hydrochloric acid, all the sulphur is not given off as H2S, and that a part either passes off as S(CH3)2 or remains behind with the solution as some organic product-was tentatively believed as indicative that the sulphur is chemically associated with the carbon and the iron. Levy (Fourn. Iron and Steel Inst., 1908, No. 2), who has done much good work in the endeavour to determine the relations which exist between iron, carbon, and sulphur, in the alloys of these elements, states, as the result of his research, that there is no conclusive evidence of any chemical union. In his tabulated results showing the amount of sulphur evolved presumably as S(CH3)2 on dissolving iron, carbon, and sulphur alloys, the maximum is o'06 per cent, but the average is very much less. Schulte, on the other hand, had found that from I per cent to 12 per cent of the total sulphur is evolved as an organic sulphur compound; and Bischoff found an even greater quantity. The results are apparently conflicting, and it is evidently obvious that more research is required in this direction. It has been shown by Arnold and McWilliam, and confirmed by others, that carbide of iron does not decompose into graphite and iron during the annealing of steel until it segregates into relatively large masses. Taking this as a basis Mr. Levy has advanced an explanatory hypothesis as to how it is that sulphide of iron prevents the decomposition of carbides in white irons. He had found that during the solidification of irons free from silicon and manganese, but rich in sulphur, "the sulphide separates at a temperature in the neighbourhood of 1130° C., together with, and as a component of, the austenite-cementite eutectic, forming a triple austenite-cementite-sulphide eutectic, the cementite component of which is interstratified with a jointed pearlite (by decomposition of austenite) sulphide one." He stated that:-"The presence of iron sulphide in the eutectic introduces intervening layers, which may partly ball up on annealing, but even then leave sulphide films between the cementite crystals; these act almost as emulsifiers, preventing the coalescence of the cementite portion, which is apparently a necessary preliminary to its decomposition into free carbon and iron. These layers and films are so persistent, even on slow cooling, as to retain their position between the cementite crystals, until the metal has cooled well below the temperature of decomposition, so that an iron which might otherwise become grey is retained, even on very protracted cooling, in the white form, by sulphur as sulphide; o 25 per cent sulphur being sufficient for this purpose under the moderately protracted cooling conditions of the research. It is not improbable that the mechanical force exerted by sulphide, on separation and cooling, may also prevent the physical conditions necessary for carbide decomposition, which, as is well known, is accompanied by considerable expansion." It is to be noted that Mr. Levy's argument is based on the effect of the sulphide films in the eutectic, preventing the segregation of the cementite into relatively large masses, which, as he expresses it, "is apparently a necessary preliminary to its decomposition." His conclusions were based on the examination of hypoeutectic alloys containing not more than 2.75 per cent carbon and free from massive plates of cementite. Whilst admitting that his conclusions may be correct, as applied to the eutectic, some other explanation would be necessary if decomposition did not occur when a considerable quantity of massive cementite initially were to form in the alloy. That stable massive cementite can be so obtained in iron sulphide alloys I shall presently show. If it could be shown that sulphur in some form of combination with the iron and carbon does crystallise with the carbides, and that such mixture or solid solution is stable and not readily decomposed, it would be reasonable to conclude that the sulphur is responsible for the stability. It has been suggested that silicon in iron decomposes the carbides according to the following chemical reaction : 3Si-2Fe3C 3Fe2Si-2C. The only objection to this explanation is that the silicon is not free in cast-iron, as was proved by Turner, and, moreover, as will be shown presently, it is combined with iron in solid solution before the carbide is decomposed. They were made from Cleveland ironstone, and Gontermann (Anorg. Chem., 1908, Bd. 59) found that on | brough. adding pure silicon to molten iron, the iron and silicon contained :combined with considerable rise in temperature, and I have noticed the same thing even when adding it to carburised iron. The same authority, who has made a most careful study of the ternary alloys of the iron-carbon-silicon series, has shown that the eutectic freezing-point rises with the silicon from 1130° when silicon is absent to about 1150° when it reaches 10 per cent, and to 1175 when it is about 17 per cent, and that the carbon in the eutectic of the alloys containing between o per cent and 10 per cent silicon, falls as the silicon rises by about 0.3 per cent for each unit of silicon. The same author proved that the pearlite reversion-point in these alloys rises with the silicon on an average of about 30° C. for each unit of silicon in the alloys containing between 0 and 6 per cent silicon. He concluded, but did not actually prove, that in the region of the curve of unvarying equilibrium two cementites crystallise; one a solid solution of the carbide and silicide of iron; and a second, a mixture of this with another ternary iron-silicon carbon solid solution. Combined carbon Graphite It may be accepted that the sulphur in the white iron undoubtedly is the cause of the whiteness of the iron, whilst the excessively high silicon and low sulphur are equally responsible for the graphitic condition of the carbon in the grey irons. The micro-structure of the high silicon metal was characteristic of all phosphoretic, high silicon, carbon alloys. Curved plates of graphite cut the mass in many directions, whilst the binary eutectic of phosphorus and iron remained in irregular patches, generally midway between the graphite plates. The ground mass occupying the space between the eutectic and graphite plates consisted of silico-ferrite. If the composition of the alloy lies between the curve of saturated silico-austenite and the curve of non-varying The interesting feature about the structure of the white equilibrium, saturated silico-austenite primarily forms; iron is that there was no iron-iron-carbide eutectic. This and following this a secondary crystallisation of a binary had been replaced by the ternary eutectic of iron-phoseutectic consisting of this saturated austenite and silico-phorus and carbon, which, according to Dr. Wüst, contains cementite. A micro-examination proved the crystals to be quite homogeneous mixtures, or solid solutions. It was difficult to assign to them any definite chemical constitution. They may be considered as silico-carbides of manganese and iron, and, as will be shown presently, bear a close relation to similar crystals which primarily form during the freezing of iron-carbon-silicon alloys. Having briefly referred to the work of a number of authorities, I now propose to describe my attempts to sup plement our knowledge in this direction by a purely micro chemical research. In order to understand the remarks which follow, it is necessary to briefly describe the changes which occur when pure iron-iron carbide alloys pass from the liquid to the solid state as are indicated by the researches of Osmond, Roberts-Austen, Stansfield, and of Carpenter and Keeling. In the iron alloys containing less than the eutectic proportion of 4.3 per cent carbon, described as hypo-eutectic alloys, austenite octahedral crystallites of the fir-tree type first fall out out of solution, and these continue to grow till the liquid is so impoverished of iron and enriched in carbon that when the eutectic proportion of 43 per cent carbon is reached, the liquid solidifies, and breaks up into carbide of iron and austenite. The hypereutectic alloys, containing more than the eutectic proportion of carbon, on cooling, first yield carbide of iron crystals, and these continue to grow till, by removal of the excess carbon, the eutectic proportions of iron and carbon are reached. The eutectic in its turn then freezes. For the purpose of my research it was necessary to select pig metals, grey and high in silicon and white with high sulphur. These were kindly supplied by Messrs. Wilson, Pease, and Co., and Messrs. Cochrane and Co., Middles about: There was evidence that the primary crystals of austenite of the octahedral skeleton type had been the first to fall out of solution, that the second crystal to form consisted of short plates of carbide of iron (cementite); whilst the ternary eutectic of phosphorus, carbon, and iron was the last to freeze and occupied spaces between the cementite plates and the primary crystals. Dr. Carpenter and his assistant, Mr. Edwards, of Victoria University, Manchester, kindly obtained, for the purpose of this Address, the cooling curves of these two typical metals. These were as follows: : Grey Iron. is also coincident with important chemical changes. The The long arrest at 1118° indicates a change of state, but second long arrest at 945° is due to freezing of the iron phosphorus carbon eutectic. The arrest at 850° indicates the formation of pearlite, and corresponds closely with the arrest in a similar alloy examined by Gontermann. The at 690° is probably due to the formation of pearlite in the eutectic of iron and phosphorus, and is of great interest, for it points to the conclusion that silicon is not a constituent of the austenite of the ternary eutectic. arrest White Iron. The micro-structure and analysis help more fully to explain the arrests on cooling this alloy. The first arrest at 1149° C. is where the primary austenite crystallises with the silicon, as will be shown presently. The second arrest is where the primary cementite plates freeze. The third arrest at 945° is the freezing point of the ternary eutectic, and is identical with that of the corre sponding long arrest of the grey iron. The fourth arrest at 770° is coincident with the formation of pearlite. Bearing in mind that the manganese in the white iron was insufficient to combine with the whole of the sulphur present to form manganese sulphide, it is obvious that some other compound or compounds of sulphur existed. The microscope clearly revealed the presence of manganese sulphide and traces of free iron sulphide. The carbide plates were quite free from striations of sulphide, such as had been noticed by Mr. Levy in the eutectic of high sulphur irons. But for the sulphur present, the silicon would have been sufficient to effect a decomposition of the carbides, and the metal in absence of the sulphur would have given a grey instead of a white fracture. In view of this conclusion it appeared to be probable that if manganese were to be melted with the metal, it would combine with the sulphur associated with iron, &c., and crystallise as MnS, previous to the solidification of the carbide, or independently, and that the metal would then become grey on cooling. In order to test this, a portion of the metal was melted in a clay pot with a little pure manganese, free from carbon -sufficient to give 1 per cent of manganese, which was more than sufficient to combine with the whole of the sulphur. As soon as the mass was melted it was at once poured into a sand mould and allowed to set. When cold, it broke with a grey fracture corresponding to what is known as hard forge, and the combined carbon instead of being about 3 per cent was reduced to o 6 per cent, a result proving the correctness of the hypothesis. It is well known that when manganese or chromium and some other metals are present in large quantities in pig irons, these metals, as carbides, crystallise with the carbide of iron forming double carbides, and these are much more stable than the massive pure iron carbide. It appeared reasonable to believe that if sulphide of iron, or some ironsulpho-carbon compound, were to crystallise with the carbides it would have a similar effect. Remembering that the conclusions on this question, as to whether sulphur does or does not crystallise with the carbides, are conflicting, it is evident that the only possible way to find out whether sulphur does so crystallise is to separate the carbide from the iron and test it for sulphur. With this object, a considerable quantity of the original Cleveland white metal was crushed to the very finest powder. It was then treated with a 10 per cent solution of hydrochloric acid in water in large excess, and the action of the acid was allowed to continue until evolution of gas ceased. The insoluble matters, consisting mainly of carbides and phosphides, were filtered off, washed and dried, and were ground down in an agate mortar to a still finer powder, so as to liberate any mechanically entangled sulphides. The powder so dealt with was again treated with acid as before, after which the residue was filtered off, thoroughly washed with water, was transferred to a separate vessel, and was boiled with strong caustic-potash to dissolve any decomposition products. A second trial was made with the same metal; but, in this case, re-pounding and acid treatment were repeated three times, so as to eliminate the possibility of mechanical inclusion of sulphide or iron. The sulphur found in the remaining carbides was o'r per cent. As the manganese in this metal was not sufficient to form manganese sulphide with the sulphur, it seemed desirable to determine whether or not when the manganese is in sufficient quantity sulphur would crystallise with the carbide. For this purpose the white chilled part of a crushing roll was experimented upon. The centre part was open grey iron, and contained 3.1 per cent of the carbon as graphite. The white chilled portion contained : Combined carbon Graphitic carbon Manganese. Silicon.. Sulphur Phosphorus.. : Per cent. a result showing that only a minute quantity of sulphur was crystallised with the carbide. Whether a different result would follow if both sulphur and manganese were greatly increased has yet to be determined. Having proved that sulphur in some undetermined state of chemical combination does crystallise with carbide of iron, an attempt was made to determine the maximum amount of that element the carbide will retain under the most favourable conditions. With this object in view a considerable quantity of very pure white iron, containing only traces of silicon, sulphur, and phosphorus, and 3.5 per cent of carbon, was melted in a plumbago crucible; and when in a molten condition sticks of roll sulphur were forced under the surface of the metal, and afterwards the mixture was briskly shaken up with the sulphur which had liquefied on the surface. Precisely the same result was obtained as described by Karsten, who had made a similar experiment. A metal was produced having a white fracture and large cleavage faces. The micro-structure was similar to that of hypereutectic iron carbon alloys. Large plates of carbide cut the metal in many directions, whilst between the carbide plates was located the triple carbide-sulphide-pearlite eutectic, so accurately described by Mr. Donald Levy. The carbide plates themselves were peculiar in having circular prismatic inclusions of sulphide of iron symmetrically arranged at right angles to the sides of the plates. In horizontal sections of these plates they appeared as circular dots, sometimes arranged in continuous lines, suggesting that the sulphide had been actually in soiution with the carbide when the metal was liquid, that they fell out of solution together, the sulphide separating and segregating along the cleavages of the carbide, A portion of this sulphurous material was re-melted and | contained 1·89 −0·06 = 1.83 per cent of the silicon, or on treated with a second quantity of sulphur. This time in 100 x 1.83 addition to sulphide of iron a considerable quantity of the 100 parts of it =4'3 per cent, and that about 42'5 soot-like substance described by Karsten floated to the surface, and free graphite separated and stuck to the sides 97 per cent of the total silicon had crystallised with the of the crucible. From which we may conclude that the maximum degree to which the carbon can be concentrated by this method is about 44 per cent. In these trials the carbide certainly had sufficient opportunity to become saturated with sulphur in each case. Both of the metals were crushed to exceedingly fine powder, and were treated with acid to decompose the free sulphides. The residues were repounded and treated with acid a second time, and afterwards with strong potash solution. After this treatment, analyses of the insoluble residues indicated, in one case 0'09 per cent sulphur, and in the other o'08 per cent. From this it would appear that carbides will not carry in solid solution more than about o'1 per cent of sulphur. The metal containing 4'37 per cent carbon and I per cent sulphur, even on prolonged annealing, did not become graphite, a proof that the massive carbides present were quite stable. The microscope reveals the fact that in almost all commercial white irons containing much sulphur the greater part of the sulphur is combined with either manganese or iron, and that the sulphides mainly exist as independent inclusions. It appears reasonable to assume that the manganese sulphide is without influence on the carbon condition, and that, although iron sulphide may have some influence, in the way suggested by Mr. Levy on the eutectic, it is the sulphur that crystallises with the carbide which is mainly responsible in preventing the separation of graphite by making the carbide more stable. If it is assumed that the stability of the carbide depends on the quantity of sulphur which crystallises with it, and not on the total amount present in the metal carrying the carbides, it is clear that a great field of research is now open, the borders of which I have barely touched to corelate their stability and sulphur contents. The microscope does not show in what constituent the silicon crystallises. It is known that in grey irons it is associated with the ferrite and pearlite, but grey iron is the final result of the decomposition of carbide of iron and possibly of silico-carbides, which primarily form during solidification, and although the silicon in the decomposed product may be entirely associated with the iron it is no proof that initially some of it may not have crystallised with the carbides. In the white Cleveland iron, previously referred to, it is probable that the several constituents are present in the following proportions: Silico-pearlite, the residue of the original Iron, phospho-carbide eutectic Per cent. 42'50 33.66 23.10 0.38 0'36 austenite. A little reflection will lead to the conclusion that if the carbon in the Cleveland white iron were to be gradually increased, the proportion of primary austenite crystallites would decrease, there would be less and less of them to carry the silicon, and this element would be concentrated in the diminishing solid austenite. It also follows, that if the carbon were to be so increased that no primary austenite would form, the silicon would have to crystallise in some other constituent. In the example, referred to above, of the chilled casting, the carbides contained only o'028 per cent silicon, or o⚫016 per cent on the original metal. In this case, therefore, about 98 per cent had crystallised with the primary austenite. The question as to what amount of silicon will crystallise with the austenite so as to saturate it is probably variable with other variables. To determine this by chemical analysis would involve an exceedingly tedious research. It is probable that as it increases, and as the austenite approaches more and more nearly to the saturation point, a gradually increasing proportion of the silicon will crystallise with the carbides. It is well known that molten low silicon grey irons, in the absence of any appreciable quantity of sulphur, gives a white fracture when slightly chilled. Irons with above 5 per cent silicon, when similarly treated, are supposed not to behave in the same manner; and this is quite true when any ordinary method of chilling is adopted. For instance, when the liquid silicious glazed metal No. I was run into water, the chilled iron contained graphite; but when a large drop was suddenly pressed into a sheet as thin as paper between cold plates of iron, the chilled metal was quite white and no graphite could be detected on dissolving it in nitric acid. The metal so chilled was difficult to dissolve in acid, and the silica produced, instead of forming a gelatinous bulky residue. remained in a close dense condition-indeed the thin chilled sheet, after all soluble matter had been removed, remained a rigid sheet of dense coherent silica, whereas the same metal allowed to cool slowly from the liquid state in a sand mould yielded to acid gelatinous silica. The different behaviour to acid treatment of the chilled as contrasted with that of the slowly-cooled metal indicates that the condition of the silicon in rapidly chilled metal is different from its condition in the same metal slowly cooled. In 1895 Mr. T. W. Hogg, of Newburn Steel Works, published an account of a very interesting observation, in which he showed the difference in the silicon solubility in different parts of the same pig-iron-a portion of which was white and a portion grey. The iron referred to contained :White part. Grey part. = He determined the solubility in dilute acid of the silicon in each portion, and found that the silicon soluble in hydrochloric acid was, in the grey part about 81 per cent and in the white part about 48 per cent. He found also that the silica left on treating the two varieties of metal in acid differed in character-that from the white portion was dense, whilst that from the grey metal was much more voluminous. The white metal contained the eutectic proportion of carbon, and therefore it could not contain any austenite crystallites; indeed with the silicon o'60 per cent also present it must be regarded |