On the Chemical Composition of Harmotome. of platinum, which was added in some excess. The w then evaporated to dryness at a gentle heat; the dry gested with alcohol; the alcoholic solution mixed with w sulphate of ammonia, and evaporated to dryness. The was then ignited, and treated with hot water. The sol evaporation gave efflorescent crystals of sulphate of soda (g) As in this analysis the relative quantities of pot soda were not determined, a new analysis was underta that purpose. 13.55 grains of harmotome crystals of t form were decomposed by muriatic acid, as before, an evaporating to dryness and re-dissolving, the whole ear tents of the mineral were thrown down at once by carb ammonia. The residual chlorides obtained, as in the pr process, weighed .38. Their solution was precipitated. riate of platinum, and the liquid left to spontaneous tion. Well characterised prismatic crystals of the doub ride of platinum and sodium were formed. These were t by digestion in alcohol. The residual chloride of platin potassium, after being well washed with alcohol, and c dried, weighed .58, equivalent to .17726 of chloride of um. By subtraction we get .20274 for the chloride of On distributing, in the same proportions, the .48 of solu due of the first analysis, we get .2239 of chloride of pot and .2561 of chloride of sodium, equivalent to .14163 of and .13647 of soda. I prefer taking the total soluble of the first analysis to that of the second, because the analyzed were better formed, and of greater purity. We thus have in 16.07 grains of the mineral, exclu watermencosts credere det honom s Jay fouution mad bearsed, abog 3.351 .016 .136 13.686 Soda,... Peroxide of Iron,.. 47.04 15.24 20.85 .10 .88 .84 .24 14.92 100.11 of potash and undertaken for als of the same efore, and after hole earthy conby carbonate of in the preceding ipitated by mu aneous evaporathe double chlose were taken up of platinum and ol, and carefully oride of potassipride of sodium. 3 of soluble reside of potassium, 14163 of potash, 1 soluble residue ause the crystals rity. ral, exclusive of 7.56 2.45 3.3517 .0168 .1416 .1364 .03 13.6865 After I had ascertained the existence of alkalies in the crystals of the new form, I submitted to chemical examination by a similar process a portion of the barytic harmotome of Strontian of the ordinary form, and obtained cubical crystals, the solution of which, when mixed with muriate of platinum, and evaporated at a gentle heat, afforded on re-solution a small quantity of minute yellow scales; and by subsequent spontaneous evaporation, crystals of the chloride of sodium and platinum were formed. I then examined some small twin crystals of barytic harmotome from Andreasberg, in the Hartz, which was, I believe, the locality of the specimen analyzed by Klaproth, and obtained a like result. It seems, therefore, extremely probable, that it will be found universally, that barytic harmotome contains small quantities of potash and soda *. The existence of potash and lime in the barytic harmotome of strontian, appears to afford an additional link of connexion between the two varieties into which harmotome has been divided by foreign chemists, baryta in the one being supposed to be replaced by lime and potash in the other. The constitutions of the two varieties have not yet, however, been accurately reconciled to one another. The Berzelian formula of KS2 + 2 C S2+10 A S2+15 Aq correctly represents the composition of the lime harmotome, according to the analyses of Gmelin and * I am not aware that potash has before been observed in a proper barytic harmotome. After I had detected the two alkalies in the strontian harmo tome, I observed in Berzelius' Jahres Bericht, 6th year, p. 224, an allusion to some unfinished researches of L. Gmelin, showing the presence of soda in a barytic harmotome, but I have never seen any further account of these researches. On the Chemical Composition of Harmotome. Wernekinck. But when we substitute baryta for lime ash, the formula will not exactly apply to any of the of barytic harmotome with which I am acquainted, a it does not deviate very much from some of them. not, however, I think, draw any argument against th cation of the doctrine of replacement to these two varieti this want of perfect conformity; because the different an barytic harmotome, scarcely vary more from the formula th do from one another, and we might as well argue that the specimens of barytic harmotome which were the sub these analyses, were not the same mineral, as deny the occ of replacement between the two varieties, on the mere of this disconformity. On the other hand, the almost identity between the forms of the two varieties, the app tion between their atomic constitution on substituting on oxides for another, and the occurrence of small quant potash and lime in the barytic harmotome of Strontian, a little baryta in the lime and potash harmotome of Anna appear all to render it extremely probable that the two timately be found to admit of the application of the pri of isomorphism, or at least of plesiomorphism. We ma that future and more extended analyses will yet establ perfect conformity of the constitution of barytic harmoton that of the other variety, on making the requisite substi If this shall be the case, we can hardly doubt that the m which has been in this country called Phillipsite, ought be considered as a lime harmotome. The general form crystals, as described by Mr Levi †, is the same as that rytic harmotome; and the measurements of its angles present greater discrepancies than between the carbona lime, iron, manganese, and magnesia, substances which, doctrine of replacement has any foundation at all, must be ed as composed of plesiomorphous bodies. Neither wo seem that the variations of its cleavage can present any s obstacle; for cleavage appears chiefly of importance as bei dicative of crystalline form; and as long as the cleavage o lolo sedomsonst bedelity See Wernekinck's analysis, afterwards given. Josad +Annals of Philosophy. November 1825. motome. for lime and pot- almost perfect carbonates of On the Chemical Composition of Harmotome. 39 minerals affords forms which are identical with some of the crystalline forms which are common to both minerals,—and this is the case in regard to philipsite and harmotome,—we can hardly maintain the diversity of the two substances, merely because these cleavage-forms may not be identical with one another, if other circumstances tend to establish the connexion of the two bodies. I shall here, with the view of enabling every one to draw his own conclusion as to the probability of the ultimate reconciliation of the constitution of the two varieties, subjoin Tables containing all the analyses of the mineral with which I am acquainted, and shall annex the composition of both varieties calculated by the atomic weights of Berzelius, according to the chemical formulæ corresponding with KS2 + 2 CS2 + 10 AS2 +15 Aq for the lime variety, and 3 BS2 + 10 AS2 + 15 Aq for the barytic variety. It will be observed that the Strontian mineral approaches nearer the theoretical composition than any of the other barytic varieties, in so far as respects baryta and the other replacing constituents, which is perhaps a step not altogether without importance, towards a more perfect accommodation of the two varieties, although, as respects silica and alumina, some of the other analyses come nearer the formula. F 24.5 I may take this opportunity of mentioning, that after detected alkalies in barytic harmotome, it occurred to me amine Brewsterite again for alkalies by the same process, was applied to the former mineral; my previous research alkalies in Brewsterite having been made by decomposing carbonate of baryta, and throwing down the baryta by ca ate of ammonia, a method which renders necessary the ult expulsion by heat of a very large quantity of ammoniaca which is apt to carry along with it small quantities of fixed rides. I accordingly treated a small quantity of powdered sterite with muriatic acid, leaving them in contact for some and occasionally applying heat. By the process already d ed, I ultimately obtained a minute quantity of cubical crys and, on examining those by muriate of platinum, they se to be entirely chloride of sodium, at least operating with small quantity of materials which I used, I could not d potash. The minute quantity of soda is of course in add to strontia, baryta, and the other constituents which I form mentioned in Brewsterite. When my time permits, I inten execute another analysis of the mineral, to ascertain the e proportion of alkali it contains |