the oxide of iron, magnesia, and manganese. Lime is left as a white powder, sulphate of lime, gypsum. From the acid solution, magnesia may be precipitated by basic phosphate of ammonia; the sediment, washed and calcined, leaves phosphate of magnesia. The remainder of the acid solution contains iron and manganese, which are to be separated by gallic or succinic acid, which precipitates the iron. This sediment may be calcined, which leaves oxide of iron. The manganese is to be precipitated by caustic potash or soda; filtered, and dried. In this way we get the amount of iron in oxide of iron; the manganium in manganese; magnesia in phosphate of magnesia; and the lime in sulphate of lime. The alkaline solution of silex and clay is to be saturated with sulphuric acid, which precipitates the silex in a white powder; this is to be washed and dried. The remaining clay is yet held in solution, and may be precipitated, after neutralizing first with caustic potash, by carbonate of ammonia. If sulphur is in the ore, it may be detected. by the smell of sulphuretted hydrogen, when pouring the acid on the alkaline solution, or may be previously tested by acetate of lead. Phosphorus may be detected by letting fall a few drops of the alkaline solution into some lime-water, when phosphate of lime is precipitated, provided there is no carbonic acid present; this can be ascertained by testing the white precipitate by hydrochloric acid, which dissolves the carbonate of lime, but not the phosphate, if there is no excess of acid. A quantitative chemical analysis is very seldom insisted upon by the iron manufacturer, and is not generally considered to be actually needed. This may be, in some measure, true: but a qualitative analysis is almost necessary in every case. A good manager should be able to determine at least the quality of the matter of which his ore is composed. An analysis of this kind is very easily effected; and we shall describe a simple method by which the component parts of any kind of iron ores may be discovered. Iron ores are of various colors, and occur in the most various forms. The following is the most simple test by which a given specimen of mineral may be determined: Put it into a slow burning fire, say a common grate fire, and there leave it for twentyfour hours. If, at the expiration of that period, it shall have turned red or brown, it may be considered iron ore. We may also conclude that it is iron ore when, in turning black, some fragments of it are attracted by the magnet. If the substance shall have turned white, it will be either wholly or in greater part lime; which, how ever, may be very useful under circumstances where calcareous ore is needed. This is an easy practical method of arriving at an estimate of a mineral species; but, with the exception of the iron it contains, leaves us quite in the dark as to its component parts.. If any specimen is proved to contain iron in sufficient quantity to justify the manufacturer in smelting it, it is of great consequence to know the foreign matter associated with it. To determine this point, we proceed as follows: Sulphur exists in most iron ores, particularly the hydrates, either in the form of sulphates or sulphurets. To find sulphur, a portion of ore is pounded and passed through a fine silk sieve, and then washed with a large quantity of rain water, which must be previously freed of sulphuric acid by chloride of barium. The washwater of the powder, which may be boiled with the ore, is set to rest, that the iron may subside; and part of it is then tested with chloride of barium. If a white precipitate falls, we may conclude that the ore contains sulphuric acid. In some ores, particularly the yellow hydrates, sulphuric acid is not so readily detected. In such cases, we must dry the washed powder, and expose it to a gentle heat until it reddens, and again pour it into the water. If, after this, it shows no signs of a precipitate with chloride of barium, we may conclude that no sulphuric acid is present. Chlorine is found in the same way, with the only difference that we use nitrate of silver as a precipitant. If a white precipitate falls directly, we may expect that the ore contains a large amount of chlorine. But a small quantity of chlorine will manifest itself only after one or two days' exposure of the solution to light, when it will gradually darken from violet to black. We may expect to find sulphuric acid and chlorine in the hydrates of the coal formation. Sulphur, in the form of sulphurets, may be detected by boiling the powder of iron ore in a solution of potash, which dissolves the sulphurets; and by testing that solution, when clear, with acetate of lead. If there is any sulphur in the ore, a black precipitate of sulphuret of lead will form directly. The powder of ore, thus freed from sulphuric acid, chlorine, and sulphur, may now be dissolved in hydrochloric acid; this acid will dissolve everything but sulphate of baryta, sulphate of lime, silex, and carbon. Carbonic acid will escape with effervescence, and is easily detected. If the insoluble residue is white, we may expect in it sulphate of baryta, silex, and a little alumina. It cannot contain sulphate of lime, for, as this is soluble in water, it would, of course, in our first experiment, have been decomposed by chloride of barium. The residue may be melted; fused with four times its weight of a mixture of carbonate of potash and soda, in a silver or polished iron crucible; soaked in water, boiled and filtered; and then saturated with hydrochloric acid. If a precipitate falls, it is silex; while the remaining portion of the dissolved residue must be sulphate of baryta. Different soluble compounds may now be employed to test the first hydrochloric solution. The application of oxalate of ammonia to a few drops of this solution, largely diluted with water, will show the presence of lime; and caustic, or carbonate of ammonia, that of alumina and chromium. Sulphuric acid will precipitate barytes and lead. A bright iron wire, or blade of a knife, held in the solution for a short time, will show the presence of copper, by giving a coating of copper to the polished iron. Magnesia it is somewhat difficult to detect; but, if it is not in too small amount, it may be detected by boiling the solution, from which baryta and lime have, by the above tests, been previously removed, with carbonate of soda; but more effectually, if we precipitate all the substances in a part of the solution by carbonate of ammonia, and remove the baryta by sulphuric acid, and the lime by oxalate of ammonia, neutralize by ammonia, and then precipitate by phosphate of soda, which throws down a basic phosphate of ammonia and magnesia. Acetate of lead is a very valuable reagent; it forms with any of the chromic solutions a yellow precipitate; with phosphoric acid a white, and with sulphur a black, precipitate: but with a hydrochloric solution, it would form a white sediment of chloride of lead soluble in excess of potash; while the sulphuret, chromate, and phosphuret are insoluble in that menstruum. If there is any zinc in the ore, it may be found, after the iron is precipitated, by sulphuretted hydrogen, provided the solution is previously neutralized; this precipitates a white sulphuret of zinc. For the purpose of detecting zinc, it is necessary to remove iron and everything else, by saturating the acid solution by ammonia, and by then testing with sulphuretted hydrogen. The most common compounds in iron ore are yet left to be found; these are manganese and phosphorus. Manganese is with difficulty separated from iron; and to effect this separation, we recommend the solution of the iron ore in hydrochloric instead of nitro-hydrochloric acid, because in the latter case the salts of manganese are very apt to oxidize more highly than protoxide, and are then inseparable from iron. If the solution of the ore is acidulous, the manganese will be in the form of protochloride of manganese, and may be separated from the iron by boiling the solution to dryness, and by expelling all the superfluous acid. On redissolving it in water, only the salts of alkaline and alkaline earths will be dissolved along with the manganese, and very little of the iron; this iron may be precipitated by succinic or benzoic acid, provided the solution is neutral. After this we may detect iron by means of ferrocyanide of potassium, which, if the iron is all removed, ought not to change the color of the solution, but form a white precipitate with manganese. In a solution free from iron, the manganese will be precipitated by ammonia or carbonate of ammonia, which throws down a double salt of manganese and ammonia. For the same reason as that given above, we recommend the solvent, hydrochloric acid, in an iron ore analysis, as the means of detecting phosphorus. The hydrochloric solution of iron, &c., may be neutralized by ammonia, which separates the earths and a part of the iron, but leaves the phosphates in solution. The solution may be tested by chloride of barium, which produces in a neutral or alkaline solution a white precipitate of phosphate of barytes; this is redissolved by adding hydrochloric or nitric acid. Other foreign matter in iron ores is of little consequence, and need not be taken into consideration. Those acquainted with the use of the blowpipe are able to detect sulphur, phosphorus, arsenic, zinc, and other substances, more easily with that instrument than by any other means; but no directions are needed to guide their manipulation, for we shall assume them to be masters on this subject. Poor ores, especially clay ores, are sometimes difficult of assay, even though we simply want to know the amount of iron contained in them. The clay ores require an uncommon amount of alkaline flux, and lime is not sufficiently strong to flux the alumina; we are therefore compelled to make use of potash or soda. Both are very apt to perforate the crucible. A mixture of potash and borax answers. better; but if too small a portion is used, all the iron is not revived; and if too much, the crucible is destroyed before the iron begins to melt. In such cases, the best plan is that prescribed by Fresenius, that is, to mix the powdered and calcined ore with cyanide of potassium, and to smelt the ore, and revive the iron, in a porcelain or platinum crucible, over a spirit-lamp, in which case an excess of the flux is of but little danger. This mode of analyzing is particularly useful where arsenic is combined with the ore, for it will reduce the |