This observation however, is limited to a comparison of the actual cost involved in the smelting of such ores as those of the Cleveland hills, and of the purer hematites of the north-west of England, or those of Spain and elsewhere. Of course this margin is liable to fluctuations of a very great magnitude, when the demand for the finer kinds of iron rises, as it has done recently, in excess of the supply. In Mr. Holley's report of the practice at Essen, he sets down the loss at 2.5 per cent., which coincides pretty nearly with my own practice; and this with the cost for coal, repairs, ore, labour, etc., will bring the total expense up to about 6s. or 7s. per ton. M. Peterson of Eschweiler gives the following as his estimate:-18 to 30 of ore per 100 of pig, according to the quantity of phosphorus contained in the iron; coal about 2 cwts. per ton of crude iron. Assuming Cleveland pig iron to be bought at 15s. per ton below the price of the purer qualities made from hematite ore, it would appear that in the absence of any better method of treating phosphoric iron such a process as that just described might be employed with advantage.

In the experiment with the converter described in page 395 and undertaken with a view to reduce the acid composition of the slag, oxide of iron was the base employed. Failure attended my researches in this direction, because the basic addition corroded the silicious lining so rapidly, as to maintain in the cinder an excessive amount (above 45 per cent.) of silica. The want of success which had attended the attempts of Dr. Siemens and others to use other linings than silica deterred me from prosecuting any expensive trials as to a better mode of protecting the vessel itself.

Mr. G. J. Snelus had in the year 1872 met with a certain amount of success in lining a small converter with lime; and during his experiments he undoubtedly had observed that the neutralising of the silicic acid by this earth exercised a marked effect, in reducing the quantity of phosphorus as contained in the pig iron. Either this success, commercially speaking, was not sufficiently marked, or other circumstances deterred Mr. Snelus from prosecuting his work with the spirit which a further inquiry has led many competent judges to believe it deserved. Messrs. Thomas and Gilchrist, in the years 1878 and 1879, read before the Iron and Steel Institute papers descriptive of their work in the use of lime in the converter. They also use a vessel lined with lime,

as first suggested by Mr. Snelus, or with a mixture of magnesia and lime; but, inasmuch as something like 20 parts of quick lime have been found necessary for the treatment of 100 of Cleveland pig iron, it is clear it would not do to have to depend on the lining for furnishing so large an amount of the calcareous base; even were it capable of affording it which is perhaps doubtful. This has led these gentlemen to add lime to the charge, for the avowed purpose of neutralizing the silica formed during the blow-an object which is not so conspicuous in Mr. Snelus' original publication bearing on the subject.1

The use of lime in the converter, suggested in the manner just described, has led to a large quantity of phosphoric pig iron being now used for the manufacture of steel rails. Indeed as regards the quality of the product, so far as chemical composition and the ordinary mechanical tests enable us to judge, there is no reason whatever for supposing that it differs from the steel made from hematite iron. According to information supplied to me by Mr. Percy Gilchrist the works now using the Basic process produced in the half-year ending 31st March, 1883:—

The extent to which this Basic process will take the place of its acid predecessor must of course depend on the difference in price between the two kinds of pig-iron-the greater this difference, the greater will be the margin to cover the larger waste and additional expenses connected with the Basic mode of treatment. At Middlesbrough this difference of cost of production of the crude metal is about 10s. to 15s. per ton, whereas in Westphalia and the East of France it is sometimes almost double this amount. Accordingly in certain localities this new process has been adopted much more rapidly than in the United Kingdom.

In speaking of the development of this recently introduced branch of industry, it would be unpardonable to omit mentioning the claims of Mr. E. Windsor Richards in its promotion. For half-a-dozen years

Mr. Snelus and Mr. Thomas received Bessemer Gold Medals for their inventions in 1883 from the Iron and Steel Institute.

after Mr. Snelus' first specification, no notice was taken by the steelmakers of this gentleman's invention. This however may be excused by the circumstance of its value, as a means of removing phosphorus, not being very clearly stated. Fortunately when Messrs. Thomas and Gilchrist brought their ideas before the public, Messrs. Bolckow, Vaughan, & Co. had just erected a very large steel rail mill on the banks of the Tees, and it was fortunate for the inventors, that this work was being carried out under the direction of Mr. Richards. No one who is acquainted with the difficulties which were encountered in the practical application of what may appear a simple matter, will deny that to this gentleman and to the enterprise and boldness of his Directors merit is due not inferior to that of the originators of the process itself.

Messrs. Thomas and Gilchrist appear to fix 20 per cent. of silica in the slag, as the limit to which this substance can be permitted to attend without prejudicially interfering with the removal of phosphorus. These authorities, and also Mr. Snelus, insist on the formation of a highly basic slag, so as to present a strong base with which the phosphoric acid may unite at the moment of its formation. Messrs. Thomas and Gilchrist further give us to understand that a sufficiency of lime prevents the necessity of "over-blowing;" which may be presumed to mean that it avoids the evil of wasting metallic iron, and the consequent admission of oxide of iron into the cinder.

We are indebted to Mr. E. W. Richards of the Eston Works, and to M. M. Massenez and Pink of Hörde, for much valuable information in the practise of this now so-called Basic process. From it we learn the nature of the gradual changes experienced by iron, in the presence of lime, while throwing off the manganese and the four metalloids with which it is associated while in the form of pig.

The following table, and an appropriate diagram, were communicated by Mr. Richards to the Iron and Steel Institute at Liverpool in 1879, in connection with his experience in removing phosphorus by the Basic treatment.

Oxide of iron...

Difference Lime, magnesia, alumina, and oxide of manganese

33.20 42.75 37.60 38.21 38.66 30.66 32.63 7.26 2.57 5.91 6.17 7.89 13.43

14:59

59.54 54.68 56.49 55.62 53.45 55.91 52.78

100.00 100.00 100.00 100.00 100.00 100.00 100.00

Two heats, blown from Cleveland iron in my presence, at Eston, gave before the addition of spiegel the following results:

The Diagram No. 3 in the series, given at page 388, is constructed upon the same principle as that adopted in this work for the other processes of treating pig iron, and it shows in a blow of Basic Bessemer steel the percentage rate at which the metalloids are removed from the iron.

The analyses of the metals and slags which have been blown under the Basic treatment leave no doubt that the phosphorus originally in the pig is acidified, and transferred to the slag as a phosphate. Up to this time however those who have examined the subject most frequently are not agreed as to whether the phosphoric acid is combined with lime, or with oxide of iron.

Experiments by M. Pourcel, described by him in a very able paper,1 prove apparently beyond all doubt that at high temperatures cast iron decomposes phosphate of lime. It is somewhat improbable therefore that, were the phosphorus in pig iron acidified in a converter, it would combine with lime in preference to oxide of iron, if in the presence of the latter base. On the other hand, it is equally difficult to see how, in the absence of oxide of iron, acidification of the phosphorus can be accomplished. The lime cannot be regarded as a possible source of the oxygen required, and it is certain that air blown through melted cast iron will oxidise the metal before the phosphorus is sensibly affected. Phosphate of iron may no doubt be formed in the first instance, which if decomposed by lime would give phosphate of lime and oxide of iron. This oxide of iron if reduced by carbon or silicon might then pass as metal into the steel.

In respect to the source of the oxygen required for acidification, there is perhaps little, if indeed any, difference of opinion; but while M. Pourcel gives good reasons for believing that the phosphoric acid is combined with iron in the cinder, Mr. Stead,1 who has had ample opportunity of examining the subject at the works of Messrs. Bolckow, Vaughan, & Co., arrives at a different conclusion; and certainly his opinion is one we cannot disregard.

It may appear of little moment by what precise mode of action the phosphorus is transferred to the cinder, so long as it is effectually removed from the iron. There is connected with the question however one point of some economic importance; for, if lime could at once lay hold of phosphoric acid, however formed in the process, overblowing and the waste of iron consequent thereon might possibly be dispensed with. If, on the other hand, phosphate of iron must first be generated, it seems probable that an additional waste of metal, as compared with the ordinary Bessemer blow, is unavoidable.

'Journal Iron and Steel Institute, 1879, No. 2.