LONDON AND EDINBURGH PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE. [THIRD SERIES.] MAY 1836. LXVI. On the Action of Hydrochloric Acid on certain Sulphates, and particularly on the Sulphate of Copper. By ROBERT KANE, M.D. M.R.I.A.* THE HE following experiments were instituted in consequence of some results casually arrived at, whilst engaged on another subject; and as they possess a certain interest with regard to the theory of the hydracids, and are also additions to the number of real facts in chemistry, I have considered them deserving of the notice of the Royal Irish Academy. When bluestone (S+ Cu) +5 H, is dissolved in liquid muriatic acid, there is produced a considerable reduction of temperature, viz. from about 65° to about 35°. The solution becomes deep grass green, and by evaporation yields needles of hydrated chloride of copper. If there is taken a quantity of sulphate of copper corresponding to the atomic weight, and a quantity of liquid muriatic acid corresponding to an atom of dry acid, and the solution be effected by heat, on cooling, the whole solidifies into a fibrous mass of hydrated chloride of copper, and there is no bluestone remaining undecomposed. The sulphuric acid remains in the water. When the atomic proportions are not accurately preserved, small crystals of bluestone are scattered through the mass of chloride; but the latter can be obtained pure by carefully attending to this point. In this reaction we have evidently a complete in* Communicated by the Author. Third Series. Vol. 8. No. 48. May 1836. 2 N version of the ordinary rules of chemical affinity. The sulphuric acid ranks much higher in affinitary [?] power than the muriatic acid, and yet is completely displaced by the latter from its state of union with the black oxide of copper. The theory of this reaction is very easily understood. These are (S+ Cu + 5 H) + ClH, and there are formed (Cl + Cu) +S+6H. The sudden liberation of the larger quantity of water from its state of solidity in bluestone produces the remarkable reduction of temperature. I have sometimes observed that when the crystallized chloride of copper is allowed to remain for a long time in contact with the strongly acid mother-liquor, a reverse action is set up, and small crystals of sulphate begin to appear disseminated through the mass. I several times analysed these crystals, in order to ascertain whether a sulphate of the chloride of copper, like Peligot's chromate of the chloride of potassium, would be formed, but without effect; no definite compound could be detected. The interesting nature of this reaction made it important to ascertain the action of sulphate of copper upon dry muriatic acid gas. The experiments for this purpose were conducted in the following manner. A bulb tube was connected at the ends with strong glass tubes containing fragments of dried chloride of calcium. The one tube was by its other extremity connected to a retort, in which muriatic acid gas was disengaged by the action of oil of vitriol on fused chloride of sodium. The other desiccating tube was of much smaller size, so as to allow of being weighed in a delicate balance; to the remote extremity of this a small quill tube was attached, by which the excess of gas made its escape. The sulphate of copper in fine powder was introduced into the weighed bulb tube, and the whole then weighed to determine the quantity employed; the desiccating tubes were then attached, and the muriatic acid gas disengaged. Having been dried in its passage over the first chloride of calcium, it came into contact with the bluestone, by which it was rapidly absorbed; and any water that was formed or disengaged, carried away by the current of dry gas in excess, was deposited in the small desiccating tube, where its quantity could be accurately determined. When the crystallized bluestone (S Cu+5 H) in fine powder is put into the tube, it absorbs rapidly the muriatic acid gas, and becomes grass green: great heat is produced. Drops of moisture appear on the cold portions of the tube. It loses its pulverulent texture, and is converted into a mass of silky pale green crystals: on the heated portious of tube, points of a chocolate brown matter are produced. The current of gas being continued until all action ceased, and the tube and its contents had cooled to the ordinary temperature of the room, the apparatus was weighed, and the bluestone was found to have absorbed rather more than one atom of muriatic acid, the excess being attributed to the quantity absorbed by the water disengaged. The mass of green crystals thus obtained is very deliquescent, excessively acid, and gives fumes, arising probably from some muriatic acid in excess. Dissolved in water it yields by crystallization the hydrated chloride of copper in long needles. When there is used sulphate of copper, either quite dry, or retaining one atom of water, the effect is so nearly similar as to allow of the same description serving for both. S Cu or S Cu H absorb muriatic acid rapidly, and assume a dark chocolate brown colour. The mass becomes slightly coherent as if some water became free; but the second desiccating tube does not increase in weight in any perceptible degree. The process is accompanied by the evolution of so much heat as occasionally to crack the tubes; but the passage of the gas must be continued for a long time after the whole has become cold. The amount of gas absorbed then approximates very closely to one atom, but it seldom absolutely attains the theoretical quantity; it can approach, however, within one per cent., and we may consequently consider that one atom is the quantity absorbed. This brown matter is possessed of interesting properties. When heated it gradually and readily parts with its muriatic acid gas, leaving behind the sulphate of copper unaltered. Exposed to the air it rapidly absorbs water, with the evolution of heat, and becomes apple green, a change which occurs instantaneously if a few drops of water be allowed to fall upon Dissolved in water it forms an apple green solution; and by crystallization gives the crystallized chloride of copper, sulphuric acid remaining in the liquor. it. Two theories may be conceived of the nature of the body thus formed: One, that the chloride of hydrogen is absorbed by the sulphate of copper and combines with it as water would do,-that, in fact, the so-called muriatic acid is capable of replacing the water of crystallization of salts as ammonia and phosphuretted hydrogen have been shown to do by Rose and Graham: The other, that the chloride of hydrogen reacting on the oxide of copper forms water and chloride of copper, while the latter with the sulphuric acid constitutes a sulphate of a chloride. The general nature of its properties inclines me to believe the former to be the true idea, that the chloride of hydrogen exists as such in the brown powder, and that chloride of copper is only formed when the decomposition is effected with the presence of much water. The singular results of the reaction just described rendering an examination of the influence of muriatic acid on the sulphates in general highly interesting, experiments were instituted, of which the results shall be very briefly stated. Dry muriatic acid was passed over sulphates in the apparatus before described. With the sulphates of potash, soda, zinc, magnesia, iron, alumina, and lead, no action was observed; these salts did not change in weight or in appearance. On the other hand, the sulphates of nickel and of quicksilver absorb muriatic acid very gradually, with the evolution of heat, the absorption ceasing when half an atom has been taken up. These compounds lose the gas they had absorbed, by exposure to the air during some time, and immediately on being heated. If they be put into water, the sulphate is deposited pure, the muriatic acid remaining in the water. Sulphate of potash dissolves in liquid muriatic acid with some evolution of heat; and if by means of heat two atoms of sulphate of potash be dissolved in a quantity of liquid containing an atom of real muriatic acid, there separate on cooling finely formed crystals (rhomboidal plates) of bisulphate of potash, with opake cubes of chloride of potassium. A great number of analyses of the crystals obtained by such reaction was made to determine whether the sulphate of chlorkalium corresponding with the chromate had any existence, but no trace of its being formed could be obtained. Bisulphate of potash crystallizes from its solution in liquid muriatic acid unaltered. Sulphate of ammonia similarly treated gives precisely similar results. It has been long known that Glauber's salt treated with muriatic acid constitutes a powerful freezing mixture, the theory of which is at once explained by the results of the experiment. When sulphate of soda is dissolved in liquid muriatic acid there are formed bisulphate of soda and chloride of sodium, and as the former salt crystallizes only with four atoms of water, the remaining quantity of the water of crystallization of the Glauber's salt is disengaged, to the amount of sixteen atoms: thus, 2 {(S+ Na) 10 H} + (Cl + H) = {(2 S+Na) +4 H)} + (Cl + Na) + 17 H. This large quantity of water suddenly separated from a state of combination in which it had been solid, produces, by its absorption of caloric of liquidity, the frigorific property. The sulphates of zinc and magnesia dissolve in muriatic acid, and by cooling or evaporation are obtained unaltered. The muriatic acid does not appear to produce any change of nature. When protosulphate of iron is dissolved in muriatic acid, the liquor furnishes by crystallization quantities of unaltered sulphate and of chloride of iron. Sometimes the sulphate retains its common quantity of water of crystallization, but at others I have obtained a salt giving by analysis: The crystals were always so aggregated that their form could not be accurately determined; they are transparent, harder, and of a much lighter green than ordinary copperas ; they are quite permanent, and when dissolved in water give sulphate of iron with the ordinary quantity of water. The sulphate of alumina crystallizes unaltered from its solution in muriatic acid, but in more beautiful plates than from water. From the solution of sulphate of nickel or of mercury in muriatic acid, these salts are deposited by crystallization unchanged. 23, Lower Gloucester Street, Dublin: March 25, 1836. LXVII. An Abstract of a Memoir on Physical Geology; with a further Exposition of certain Points connected with the Subject. By W. HOPKINS, Esq., M.A., F.G.S., of St. Peter's College, Cambridge. [Continued from p. 281, and concluded.] HE two systems of fissures which I have described IV. THE are those which must be regarded according to this theory as primary phænomena, from which, as before stated, the secondary phænomena of mineral veins, faults, anticlinal lines, &c., must be derived. For this second part of the subject, I must refer to the second Section of my Memoir, where I have entered in detail into the manner in which these latter phenomena may be conceived to be derived from the former. The number of phænomena which we are thus enabled to account for, as the consequences of a simple cause from which |