348 MR-J. ARTHUR PHILLIPS Nov. 18 1850. RICHARD EsQ.,President in the Chair. PHILLIPS The following presents were announced cc The Improvement of Land by Warping Chemically considered by Thornton J. Herapath :” by the Author. A donation of 199 volumes by Mr. Griffin; see page 412 ? The following Papers were read “On the claims of the elementary substances Silicon and Selenium to be ranked among metals:” by Mr. Richard Adie of Li-verpool. ((On the existence of Copper and Lead in the Blood and in other portions of the Animal Organism :” by Mr. J. Denham Smith. XXVIIL-On Potasso-gypsite a double Sulphate of Potash and Lime. By J. ARTHUR ESQ. PHILLIPS This substance is obtained as a secondary product in the manu- facture of tartaric acid and it will therefore be necessary to describe the circumstances under which it is produced before detailing the properties and composition of the salt itself.Tartaric acid is as is well known made from the impure bitartrate of potash which reaches this country in such a state as to yield on an average 72 per cent of crystallized acid. The processes employed in the manufacture are briefly as follows Into a large tun capable of containing about three thousand gallons of water are thrown from fourteen to fifteen hundred pounds of mashed chalk which is agitated by means of a revolving arm until the water and carbonate of lime have become perfectly incorporated and a finely-divided mixture is obtained. When this is effected about two tons of crude tartar are added by means of an air-tight trap on the top of the vessel and by the aid of heat obtained by blowing ON POTASSO-GYPSITE.a jet of steam into the mixture and constant agitation of the mass the bitartrate of potash is made to transfer its free atom of acid to the lime giving rise to the formation of insoluble tartrate of lime soluble tartrate of potash and the evolution of carbonic acid which is conveyed away in leaden pipes to be employed in making bicar- bonate of soda. As soon as the decomposition is completed a sufficient portion of sulphate of lime from a preceding operation is added for the purpose of decomposing the neutral tartrate of potash in solution. By the aid of heat and long-continued agitation this is at length effected and the vessel then contains a solution of sulphate of potash together with the insoluble tartrate of lime and small portions of the carbonate and sulphate of the same base arising from the excess of these reagents originally employed.At this period of the manufacture the agitation is arrested the liquor is allowed to settle down and the sulphate of potash drawn off from the tartrate of lime which remains at the bottom of the tub. This is subsequently washed with three successive waters which are added to the solution of sulphate of potash at first obtained. The insoluble tartrate of lime is afterwards decomposed by mlphuric acid with formation of sulphate of lime and production of free tartaric acid which is crystallized in the usual way whilst the sulphate of potash with which we are at present most interested is conveyed away by large leaden gutters for evaporation.At the manufactory of the Messrs. Pontifex these liquors are first drawn in’to a large tubular steam-boiler heated by the waste heat escaping from a set of coke-ovens. In this the potash solution is con-centrated to about two thirds of its oiiginal volume and then allowed to run into a series of large bacs containing coils of iron pipe which are supplied with steam by means of the boiler in which the liquor is concentrated and in these the evaporation is completed. This boiler for concentration and supplying the steam-coils gradually becomes coated by a hard deposit in order to remove which it becomes necessary at intervals of about three months to stop the ovens and run out the liquor.On these occasions the cooling of the boiler and its contents is extremely slow as the mass of brickwork which surrounds it renders the loss by radiation very inconsiderable. When it has sufficiently cooled and the liquor has been run off the greater part of its internal surface is found to be covered with transparent lamellar crystals formed on a hard crystal- line gangue. These are sparingly soluble in water but are easily dissolved by dilute hydrochloric acid. A qualitative analysis showed them to consist of lime potash 350 SIR. J ARTHUR PHILLIPS water and sulphuric acid and a quantitative examination gave the following results FIEST ANALYSIS. 10.05 grs.gave 14*85 grs. platinum-salt. J? 93 3.05 , carbonate of lime 9.28 , 0.51 , water. >> 13.22 ,? sulphate baryta. SECOND ANALYSIS. 10.23 grs gave 15.10 grs. platinum-salt. 3.10 , carbonate of lime. 29 93 5.81 , 0.33 9 water. 8.21 , sulphate baryta. 39 ,5 These numbers afford the following perceiit age results Potash . . 28.52 28.57 Lime . 16.99 16.96 Sulphuric acid . . 48.94 48.55 Water . 5.51 5.67 9996 99.75 The above relations would lead to the empirical formula KO SO,+CaO SO,+HO as may be seen by comparison with the following calculated amounts No. of eqs. Amounts. Percentage. Potash . . . 1 = 47 28.67 Lime. . . . . 1 = 28 17.02 Sulphuric acid . 2 = 80 48.82 Water . . . 1 = 9 5 -49 100~00 Since however a variety of sulphate of lime expressed by 2(CaO SO,) + HO has been found under nearly similar circum- stances,* it appears probable that in reality the water is divided between the sulphates of lime and potash and that the crystals are composed of a double di-hydrated salt of which the true formula is * Johnston Phil.Mag. J. XLII. 325 ; also J. Pr. Chem. XVI 300. ON POTASSO-GYPSITE. represented by 2 (KO SO,) + HO + 2 (CaO SO,) t HO arid to this I propose to give the name of Potasso-gypsite. Professor W. H. Miller of Cambridge who has had the kindness to examine the crystals of this substance dcscribes them as follows PRISM AT1C. Symbols of the simple forms a 100 e 101 u 102 m 110. Angles between normals to the faces ea .. . 46O 28' ee' . . . 87 4 n ua . . 76 38 uu' . . . 26 44r ma . 52 58 mm'. . . 74 4 The crystals exhibit faint indications of cleavage parallel to a plane perpendicular to the faces a gn. The faces a are striated parallel to their intersections with the faces rn. The crystals are very thin in a direction perpendicular to the faces a. The optic axes lie in a plane perpendicular to the faces a rn. Seen in air through the faces a they appear to make angles of 22O 45' with a normal to a and an angle of 45O 30' with each other. The crystalline gangue on which the regular crystals are formed was f'oound on analysis to yield the following results FIRST ANALYSIS. 28.95 0.23 silica. 12.49 carbonate of lime.1.19 phosphate of magnesia. 37)'86 2.95 carbonic acid. 41.96 sulphate of baryta. 39-63 platinum-salt. 0.31 chloride of sodium. 0.30 oxide of iron. O*l& alumina. 9 75-83 0.58 phosphate of magnesia. MR J. ARTHUR PHILLIPS SECOND ANALYSIS. 26.23 0.25 silica. 0.28 oxide of iron. J> 0.21 alumina. >> 0.87 phosphate of magnesia. 25.57 1*90 carbonic acid. 24.12 26.20 platinum-salt. 0.30 chloride of sodium. 9.34 sulphate of baryta. 0.17 phosphate of magnesia. I. 11. Potash . 20.18 20.93 Soda . 0.43 0.61 Lime . 24-16 >> Magnesia. . 1-50 1*24 Alumina . . 0.74 0.80 Oxide of iron . 1.24 1-06 Silicic acid . 0.79 0-80 Sulphuric acid . . . 38.08 38.66 Phosphoric acid 0.49 0.42 0 Carbonic acid .. 7.79 7.87 4.31 Water . 0 >1 Organic matter traces traces 99.71 !l!hese numbers indicate that the uncrystallized portion of the deposit consists of the same substances as the crystals themselves; and if in the first analysis we so arrange them as to form the double sulphate above-described the following percentages will be obtained I. 11. New salt . 64-76 Sulphate of lime . 11.57 Carbonate of lime 1406 Phosphate of lime . 1*06 Carbonate of magnesia . 3.10 Silicate of potash . 2.42 Oxide of iron . 1 *24 Alumina . 0.74 Water . 0.76 Organic matter traces 99.71 ON POTASSO-GYPSITE. In the analysis of the crystala of the pure salt the water was esti- mated by heating to redness in a platinum crucible a portion of the substance which had been kept until it ceased to lose weight under the receiver of the air-pump in which was placed a dish of strong sulphuric acid.The same portion of substance was then dissolved in dilute hydrochloric acid and the sulphuric acid thrown down as sulphate of baryta by chloride of barium in the usual way. A second quantity of substance was then taken and after dissolving it in dilute hydrochloric acid and adding ammonia the lime was precipitated in the form of oxalate and weighed as carbonate. The filtrate from the oxalate of lime was then evaporated to dryness and the residue heated to redness to expel the ammoniacal salts. A slight excess of hydrochloric acid was afterwards added and the potash estimated as platino-chloride of potassium. In the investigation of the uncrystallized deposit the ordinary routine of chemical analysis was employed the phosghoric acid being estimated by the method of Fresenius and the alkalis separated from the alkaline earths by the use of hydrate of baryta.