added, but little action on the ore. On pouring nitric acid on it Nitric acid drop by drop, nitrous gas was evolved, and the black colour of the ore changed to brown. The filtered solution was of a golden yellow; and muriate of barytes threw and muriate of barytes. down from it a copious precipitate. This, which was sulphate of barytes, being collected and heated red hot, weigh ed 54 grains. gave out sulphuretted and D. a. A thousand and two grains of the ore, not yet Ore distilled, freed from the humidity it contains in the mine, were put into a glass retort furnished with a pneumato-chemical ap- carburetted hiparatus. Two hundred and twenty cubic inches of drogen. gas were evolved, which was a mixture of sulphuretted hidrogen gas and carburetted hidrogen gas. If a candle were brought into contact with it, it took fire, and burned with a blue flame. When shaken in a vessel containing water, half of it was absorbed. A solution of lead, poured into the water impregnated with it, afforded a precipitate of a deep brown, which was sulphuret of lead. tained sulphuretted ammo b. The fluid that passed over weighed 133 grains. It was The fluid conaqueous, yellowish, and turbid with slight flocks of sulphuretted carbon. Its smell was that of sulphuretted am- nia. monia, diluted with a great deal of water. Litmus paper, that had been reddened by an acid, it turned blue, and it emitted a white vapour, on bringing near it a glass rod wetted with fuming muriatic acid. A drop was let fall into a solution of lead, and the metal was precipitated brown. It was neutralized by a few drops of muriatic acid, and became slightly milky. On being filtered and evaporated two grains of sal ammoniac were obtained. c. The residuum left in the retort weighed 750 grains. Residuum conIt had the appearance of a black coally powder. Being tained carbon. burned on a test it left 90 grains, which were the carbon consumed. d. The fifth part of the remaining 660 grains, or 132 Silex precipitated from a grains, was roasted with twice its weight of caustic soda. portion of it. The mass when cold was of a greenish brown, and gave a light green tinge to the water with which I mixed it. I supersaturated it with muriatic acid, evaporated, diluted it again with water, and filtered. The silex was left behind. This, after being heated red hot, weighed 80 grains. e. The Alumine. Sulphate of lime. e. The solution that had passed through the filter I precipitated by carbonate of potash, washed the precipitate, and boiled it in a lixivium of potash, which became loaded with alumine. This earth being precipitated by muriate of ammonia, washed, and heated red hot, weighed 32 grains. f. The brown residuum, that remained in the alkaline lixivium, was dissolved in sulphuric acid, and evaporated to dryness. During the evaporation sulphate of lime was deposited, which, carefully collected, weighed two grains. The dry mass was strongly roasted, and then lixiviated. Oxide of iron. The oxide of iron, collected on the filter, was dried, moistened with a little oil, and heated red hot in a close vessel, when it yielded 14.5 grains of oxide of iron attractable by the magnet. The remaining liquor, decomposed during ebullition by carbonate of potash, gave some slight indications of carbonate of magnesia. Magnesia. Water expelled by heat. The ore burned or smoke. E. a. One hundred grains were put into a small glass retort, which was placed on a sand heat, and the fire cautiously increased, lest any gas should be evolved, or any perceptible decomposition occasioned, and that nothing but water might be raised from it. The quantity expelled was 21.5 grains. It had a very slight opal tinge, and a very faint smell of sulphuretted hidrogen. A very slight coating of sulphur too was deposited in the neck of the retort. b. The ore being dried was burned on a test; when the without flame combustion proceeded without flame or smoke, and emitted but a slight sulphurous smell. The loss in weight, which was 45 grains, represents the quantity of sulphur and charcoal burned, and perhaps too a small portion of water, that was left in the ore. Magnesia precipitated. c. The residuum was dissolved in a mixture of 200 grains of sulphuric acid, and 400 of water, evaporated to dryness, and kept at a strong red heat for half an hour. The residuum was lixiviated, filtered, and precipitated with ammonia, when 0.5 of a grain of magnesia were obtained. *This is apparently an errour of the press. According to the proportions of the constituent principles given at the end, it must have been two hundred grains. F. Ed. d. The muriate of pot ash. d. The liquor was evaporated to dryness, and the resi- Sulphate and duum heated till no more white fumes were expelled. What remained weighed 4.5 grains. It was a neutral salt, formed of a mixture of sulphate and muriate of potash. As this last salt must necessarily have been completely formed in the ore, we may admit too, that the potash of the former was not free in it, but formed a real component part of it in the neutral state. Till experiments on a larger scale shall have enabled me to determine more accurately the propertions of these two salts, I shall reckon that of sulphate to that of muriate as three to one. F. The results of the experiments above given will serve Corrections of to rectify some of our chemical ideas respecting the earthy aluminous schist of Freienwald, and those of a similar nature. received notions. tains carbon, 1. In their composition there is carbon only, but not The ore conbitumen; for they afford no bituminous oil by distillation, but no bituand when roasted in open vessels they burn like charcoal men. without flame or smoke. united with car pyrites. 2. The sulphur of the ore, which becomes oxigenized The sulphur during its exposure to the air, and thus forms the sulphuric bon in a pecuacid necessary for the production of alum, is not combined liar way: and in it in the state of pyrites, exclusively of any pyrites mixed not forming with the ore accidentally, but is intimately united with the carbon, and this in a manner with which we are not yet well acquainted. With the best lenses we cannot discover the smallest atom of pyrites in the ore, either in its natural state, or after it has been triturated and washed through the sieve with care. In this state of combination with carbon the sulphur is protected against the solvent power of alkalis, and gives no sulphuretted hidrogen gas with muriatic. acid. G. As to the determination of the respective proportions Difficult to deof the constituent principles mentioned, there is some diffi- termine the proportions of * I have observed in several coal-mines, particularly those of Fire damp not Anzin, a fact, that has probably some connexion with this men- from pyrites. tioned by Mr. Klaproth. The coal that produces fire damps does not contain any pyrites, at least perceptible to the eye; and in the same places the coal that contains a great deal of pyrites is wrought without the least danger. VOL. XX,-SUPPLEMENT. 2 B culty Sulphur and carbon. Alumine. Sulphur. Carbon. 1000 p. ore 216 alum. culty in it, arising chiefly from the intimate union between the carbon and the sulphur; as these two substances can. not be separated in the dry way, without new gaseous compounds being formed. The essential parts of the mineral, as an alum ore, are alumine and sulphur. The ordinary processes of analysis give us directly 160 parts as the quantity of alumine in 1000 of the ore. The sulphur not being obtainable in a separate state, we must deduce its quantity from that of sulphate of barytes obtained in treating the ore by nitric acid. Accor. ding to what has been said (in C), 1000 parts of the ore produced 270 of this sulphate. From this quantity 46 parts are to be subtracted, which were furnished by the vitriol and gypsum, and 20 by the sulphate of potash, admitting 15 of this sulphate in 1000 of the ore. Thus there remain but 204 parts of sulphate of barytes produced by this sulphur: but 204 parts of this salt contain 90-75 of sulphuric acid of the specific gravity of 1·85, or 67.5 of concrete acid, which are produced by the oxigenation of 28.5 of sulphur. And if (according to E b) the sum of the sulphur and carbon may be taken at 225, on deducting 28.5 for the sulphur we shall have 196.5 for the quantity of carbon. H. Admitting that 1000 parts of crystallized alum, demight produce composed by muriate of barytes, produce at a mean 945 of sulphate of barytes, we shall find, that the 28-5 of sulphur contained in 1000 of ore may afford 216 parts of alum, provided the proper quantity of potash be added. The component parts of the ore, that produce them, are not a fifth part of the mass. Less obtained the process. If the quantity of alum obtained, or even that might be from defects in obtained in the manufactories, be much less than I have mentioned, this arises from the imperfection of the process employed to produce the efflorescence of the ore during its exposure to the air. The oxigenation of the sulphur, and consequent formation of sulphate of alumine, takes place only on the surface of the lumps, and of course the greater part of the ore remains undecomposed. Component parts of the aluminous schist. I. From the preceding experiments we may infer, that 1000 parts of the earthy aluminous schist of Freienwald contain Sulphur It is very possible however, that the quantity of some of these component parts may be capable of being determined with more accuracy. As to the excess of about one per cent, which the sum total shows, this may be considered as of little importance in an analysis like the present. XII. On the Effects of Galvanism on Animals. In a Letter from DEAR SIR, My two papers on galvanism having met with an inser- Galvanic exper tion in your Journal, induces me to send a third, contain. riments. ing galvanic experiments, some of which I presume will be new to most of your readers, as I believe no one has per formed them but myself. After having killed two frogs, one by electricity, and Two frogs killthe other by immersion in carbonic acid gas, and dissected ed, one by electricity, the them in the usual manner, I endeavoured to excite them by other by fixed a galvanic trough of 50 plates, containing 350 inches sur- air, could not face, but no muscular contractions ensued. I did not (as be excited. |