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stupid at ventilation, and I know several cases where very absurd advice has been the cause of unmitigated failure.

It is hoped that this paper and these experiments are so clearly and plainly indicative of the principles involved, that they will enable any one to understand the simplest and cheapest way to ventilate a room.

XV. On the Pellets occasionally found in Pig and Foundry Iron. By ROBERT R. TATLOCK, F.R.S.E., F.C.S.

[Read before the Chemical Section, April 5th, 1880.]

ABOUT a year ago I was requested to make an analysis and examination of some pellets which had been found embedded in a pig of No. 4 iron, with the object of determining whether there was any difference in composition between them and the iron in which they had been formed, and also of ascertaining, if possible, the cause, with a view to the prevention of their production. A careful analysis of each was made, with the following results :--

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These analyses bring out a striking difference in composition between the two, the pellets showing nearly three times as much phosphorus and of combined carbon as the iron, and only about

half the proportion of silicon, while there is a very appreciable difference in the amount of graphite, the pellets containing the lesser quantity. It is but right to say that while the phosphorus, silicon, and sulphur, were determined in the pellets obtained from the identical pig of which the above is the analysis, the other ingredients were estimated in some which were taken, not from the same pig, but from the same brand of iron-made in the same works at the same time. Considering that it would be more satisfactory to have complete analyses of each from the same pig, I obtained, through the kindness of one of the large iron manufacturers near Glasgow, the necessary samples, of which I have just completed the analysis, with the following results:—

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These results entirely corroborate the previous ones, but more particularly as regards the phosphorus, the proportion of which has increased in the pellets to from three to four times that present in the iron; and the relative composition of the two is thus placed beyond a doubt.

These pellets are not unfrequently found on breaking up the pigs. They occur principally near or at the upper or flat surface, and most frequently, I am informed, in No. 4 iron. The object of examining these samples was partly to ascertain what connection, if any, they had with the hard metallic spots found on the surface of iron castings, and known technically by the name of "shagreen." My attention was first directed to the latter about five years ago, by Mr. Robert M'Alley, Public Analyist for Falkirk, who has paid much attention to the subject, and who then furnished me with the following analyses which he had made of some of these, and of the pig-iron used in making the castings which contained them :

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These analyses, made years before mine, show precisely the the same differences between the "shagreen" spots and the corresponding iron that mine brought out between the pellets and the iron in which they were found embedded, but even more strikingly-the phosphorus being nearly quadrupled, and the combined carbon doubled, while the silicon and graphite were much reduced in proportion. A comparison of all the results seems to render the conclusion unavoidable that the "pellets" and the "shagreen” are produced from the same cause. The latter, when

they appear in castings which have to be turned or planed, are a source of great annoyance, and as they appear at the surface of the metal, and are so excessively hard that no file nor tool will touch them, they are generally the means of destroying the entire casting, which must be broken up and re-melted. The ironfounders, however, have found a means of preventing them, which consists in the addition of a greater or less proportion of "scrap" castingsa process which is manifestly equivalent to a re-melting of the

iron.

The explanation of the formation of these hard bodies is perhaps difficult, but it is quite clear, from the appearance of the pellets, that they have remained in a state of fusion after the bulk of the iron had practically solidified, and this seems almost a necessity from their composition-phosphide and carbide of iron being more fusible than the purer metal, which solidifies first, leaving these compounds in a fluid state as a mother liquor, from which the comparatively pure iron has just crystallized. This fluid thereafter becomes solid, forming the little spherules or pellets, which are generally found lying quite loose in the cavities which contain them, but sometimes adhering to their walls. In fact, there seems little doubt that they are produced by an action similar to that which occurs in the Pattinson process for the desilverization of lead.

It is long since it was proposed to purify pig-iron by taking advantage of the fact that phosphide and sulphide of iron solidify at a considerably lower temperature than iron which is approximately pure; but in practice, the action is either not sufficiently complete, or the separation is not perfect enough to affect very appreciably the composition of the iron produced. About ten years ago protection was granted to Mr. A. C. Kirk, of this town, for a method of purifying iron in this way. The pig-iron used in the experiments contained about 15 per cent. of phosphorus to begin with, and the trials consisted in melting and casting a large quantity of the metal, and lifting off, by means of a crane, successive plates as they solidified. It was expected that the first plate would contain the smallest, and the last the greatest proportion of combined impurities, but about 20 analyses showed that there was scarcely any difference. The theory, however, is undoubtedly correct, and the failure in practice arises simply from the circumstances that the proportion of liquid phosphide and sulphide (or carbide) of iron separated is too small to affect the composition and quality of the remaining iron.

XVI.-Note on the Composition of a Peculiar Water.
BY DR. W. WALLACE, F.R.S.E., Glasgow.

[Read before the Chemical Section, April 5th, 1880.]

Composition of Water from a bore 100 fathoms (600 feet), near Paisley-Lower carboniferous strata.

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XVII.

On the Condition in which Sulphur exists in Coal.
By Dr. W. WALLACE, F.R.S. E., GLASGOW.

[Read before the Chemical Section, April 5th, 1880.]

Ir has been assumed that sulphur exists in coal chiefly, if not exclusively, in the form of bisulphide of iron, the presence of which can be detected in almost all varieties of the mineral. Crace-Calvert asserted, many years ago, that, in some cases at least, sulphur existed in coal in the form of a sulphate, and he gave a process for the estimation of the sulphur existing in this form. Some analyses which I have recently made have shown conclusively, however, that in some coals the greater part of the sulphur exists as an organic compound. These coals contain but a small proportion of iron-not nearly enough to form bisulphide with the iron that exists in them; and one well-known description, known as the Ell coal, was found not to contain a trace of sulphuric acid when tested by Crace-Calvert's method. The others were not tested.

The following table shows the relative quantities of total sulphur, and that existing as pyrites, as calculated from the iron found in the ash of the coal, assuming that all the iron exists as bisulphide, which is not always the case, as some coals contain carbonate of iron

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