ON "BUCKSHOT" IRON. BY F. P. DEWEY, NEW HAVEN, CONN. (Read at Amenia Meeting, October, 1877.) AT the Wilkes-Barre Meeting of the Institute, Dr. J. Lawrence Smith, in the course of his remarks on some peculiarities in the composition of irons, alluded to the so-called "buckshot" iron, and exhibited a specimen of this material. He said that when the small granules, or shot, were separated from the mass, they could be flattened under the hammer, and inferred that these particles had been decarburized by the blast before sinking into the hearth of the furnace, and thus we had the exceptional production of wrought iron in the blast furnace. I have recently obtained a characteristic specimen of this variety of iron from one of the furnaces at Orbisona, Pa. Considerable uncertainty existed as to its true nature and the conditions of its production. Its weight seemed to preclude the idea that it contained much or any slag, yet its lack of strength indicated that it was not homogeneous cast iron. At times considerable quantities had been produced, which could only be utilized by charging in the furnace and remelting. The specimen, on the freshly fractured surface, appeared to consist of flattened globules of iron cemented together by a bluish material which one would naturally suppose to be slag, and qualitative examination for lime strengthened this supposition. It was quite difficult to obtain drillings, as there was a tendency to split in several directions as soon as pressure was applied; but enough was obtained to undertake quantitative determinations. They were found to consist of two portions-one attracted by the magnet, and the other not. By repeated separation the magnetic portion was found to be 94.44 per cent., and the non-magnetic 5.56 per cent. Analyses of these gave the following results: Considering the sulphur to replace oxygen in the lime of the silicate, the oxygen ratio of the base to the acid is 2.09: 1 or 2:1; whence the formula (R'O),SiO2. The ratio between the oxygen of the lime and the oxygen equivalent of the sulphur in the sulphide is 7.09 1 or 7: 1; hence the full formula should be (CaO¡+CaS!),SiO,, A large number of separate globules were treated with hydrochloric acid, but none failed to leave a carbonaceous residue. From these experiments the specimen examined is shown to be a mixture of ordinary carburized iron, and a highly basic subsilicate of lime, and its production is doubtless caused by an excess of lime in the charge, a thick and semifluid slag being thereby formed which does not allow the perfect separation of the iron. While it is not impossible that the iron in the product of such an abnormal furnace process may sometimes be partially decarburized, it is not necessary to assume this decarburization to explain the formation of this product. For the determination of the total carbon, A. S. McCreath's method of decomposing the pig-iron with cupro-ammonic chloride and combustion of the residue in chromic acid was used, and for the graphite treatment by boiling for half an hour in nitric acid,† and combustion of the residue, as before, in chromic acid. The sulphur was determined by Dr. Drown's method of using potassic permanganate to absorb the hydric sulphide‡ evolved by the action of hydrochloric acid. REPORT ON A STANDARD WIRE GAUGE. (Read at the Amenia Meeting, October, 1877.) THE Committee on a Standard Gauge have been constantly engaged, since their appointment, in the duties assigned to them.§ They have corresponded with different persons interested in the manufacture and use of gauges in this country, and have received from several of them important information. They have also entered into correspondence with the governments of England, France, Germany, and Russia through their Consuls, and with Austria directly. The Consuls of Germany and France * Transactions, Vol. V, p. 575. Transactions, Vol. II, p. 224. Transactions, Vol. III, p. 43. have taken the greatest interest in the matter, and have communicated to your committee a large amount of valuable information relating to the gauges used in their countries. Prof. Tunner, of Leoben, Austria, one of our honorary members, has communicated information relative to the uses of gauges in Austria. The replies to the communications addressed by the English and Russian Consuls to their respective governments, have not, as yet, been received. Your committee commenced its labors, having in view to find a gauge which should be simple in its construction, not readily worn, capable of easy adjustment, and not too expensive to be used by the ordinary workman. With this in view, they have examined a large variety of gauges, and believe that all those in general use in the United States have passed under their inspection. They find, as the result of their examination, that, although there are a great number of patterns, most of the gauges in general use differ but slightly in principle. The different systems may be divided into two general classes. These are—first, fixed; and, second, movable gauges. Of the fixed ganges, there are three general types. These are, first, those made with slots, open at one end, the sides of which are intended to be parallel, as the ordinary wire gauge; second, those made with round holes in a plate, with or without a plug, corresponding to each hole to check the size, such as the Whitworth gauge, and the Stubbs wire gauge, better known in this country as the "twist drill" gauge. In both these kinds of gauges, the slots and holes are designated by numbers. The third kind of fixed gauge consists of a V, either cut into a sheet of steel, or formed by placing two bars of steel together at one end, and leaving them open at the other a fixed distance. Of the movable gauges there are two types: sliding calipers with verniers, with or without a micrometer screw for adjustment, and the micrometer screw gauge. Your committee find that the gauges which are characterized by round holes or slots, designated by numbers, are only approximately correct. They not only differ according as they are made by different manufacturers, but in a package of a dozen made by the same manufacturer there were often very perceptible and annoying differences. They find that in the gauges with open slots the sides are rarely parallel, and that there are even greater variations in them than in the gauges made with closed round holes without plugs. They find that the numbers affixed to the slots and holes vary so much, on account of the differences in the width of the slots, and in the diameter of the holes, as to be a constant source of inaccuracy, uncertainty, and annoyance. This variation has, in certain cases, been found to amount to as much as 50 per cent. of the weight of different wires of the same number which have been examined. It is, therefore, impossible to make even an approximative comparison of sizes, unless, besides the number, not only the kind of gauge, but also the name of the maker, is specified, and even then this approximation cannot be relied upon when the gauges have been worn from constant use or bad tempering. The best example of the round holes with plugs is the Whitworth gauge, which is made of a thick plate of tempered steel. Each hole of the gauge is provided with a hardened steel plug, which fits it exactly. In all the recent gauges of this kind the system of numbers is abandoned. The plug is made of a given diameter, which is stamped in figures on each one. These diameters generally, vary by thirty seconds, sixteenths, eighths, quarters, and so on, each size having a hole and plug of its own, so that a complete set will consist of as many holes and plugs as there are fractional parts. To obviate the difficulty of the indefinite repetition of the plugs, they are sometimes made so that when any two, or even three, plugs are placed together they will exactly fit the hole corresponding to the sum of their diameters. This arrangement is made to insure accuracy, as the multiplication of a very slight error would prevent even two plugs from fitting the hole corresponding to the sum of their diameWhen well made, this gauge is an instrument of precision; but it is evident that, in order to have such a gauge even moderately accurate, it must be a very expensive instrument, and altogether beyond the reach of an ordinary workman, or even of a manufactory with a small capital; and that from the indefinite multiplication of holes and plugs, it must necessarily be very cumbersome. When they are used, there must always be two such gauges, one for comparison and one for use, and when the gauge is only very slightly worn it ceases to be an instrument of precision, and is then open to all the objections of the ordinary gauge with fixed holes. ters. Your committee, very early in the course of their investigation, formed the opinion that no reliance whatever was to be placed on the numbers of gauges, as an indication of size, except for the individual gauge to which the number was attached; and that the only accurate and scientific way of expressing the size of an article to be gauged was by some expression of its diameter, which should be more exact than numbers, and which would allow of an accurate comparison of all the dimensions by whatever gauge they were taken. Your committee are supported in this opinion by the present practice among some European manufacturers who have recently acted in this matter, who have decided that a given number on a gauge shall correspond to a given diameter expressed in fractions of the legal standard of length of the country; but as, in all fixed gauges made for ordinary commercial use, the diameter can only be approximately expressed, neither the number nor the diameter is ordinarily correct, so that there is a double source of inaccuracy, as the number does not express the exact diameter, nor the diameter the number. Owing to the great liability to error, and the impossibility of correcting it, even in the most elaborate forms of this kind of gauge, your committee, early in the course of their investigation, after having themselves examined a large number, and having had communicated to them the results of examinations made by others, dismissed this class as being unsuitable, either from their defective construction, the impossibility of adjusting them when out of order, or their great cost, from their consideration as a standard gauge. Your committee next turned their attention to the V gauge, which is made by placing together two pieces of hardened steel, so that they touch at one end, but are open a given distance at the other, the numbers or diameters corresponding to the opening being graved upon one or both sides. The accuracy with which measurements can be made with this gauge when it is new, and the jaws properly tempered, adjusted, and fastened, is surprising. Exceedingly minute differences even in the diameters of the same wires can be detected and measured with great nicety, but by constant use the gauge wears unevenly. It must then be taken apart, reground, and readjusted, which will generally cost more than the gauge is worth. Your committee, while having the highest opinion of it for ordinary purposes, after some months of study abandoned the idea of recommending it as a standard gauge. Their attention was then turned to the other two kinds of gauges, namely, the sliding gauge with a vernier, with or without a micrometer adjustment, and the gauge known as the micrometer gauge. The advantage of these gauges is great accuracy. The sliding gauge with a vernier necessarily wears; but the error of wear can be ascer |
