poured out, finely pulverised, acted upon by nitric acid, and the undissolved silica separated. The lead is then to be precipitated by sulphuric acid, and the liquid evaporated to dryness, to drive off the nitric acid; the residue is to be dissolved in water, the alumina and metallic oxides precipitated by ammonia, the lime and magnesia by carbonate of ammonia, and the filtered liquid evaporated to dryness. The residue is to be strongly heated in a porcelain (not platina) crucible; what remains dissolved in water; the sulphuric acid precipitated by baryta water; and the new liquid, being filtered and evaporated, gives pure lithia. M. Quesneville very strongly recommends the use of nitrate of lead in the analysis of alkaline minerals, according to M. Berthier's proposal*. 16. ON THE SUBMURIATES OF IRON, AND OTHER SUBSALTS. (Mr. Phillips.) Whilst dissolving moist precipitated peroxide of iron in muriatic acid, Mr. Phillips observed that much more oxide was taken up than he had expected, and, after repeated additions, he obtained a very deep red-coloured solution, having little of the well-known chalybeate taste, and of the s. g. of 1.017; it was not decomposed by the addition of water, or by heat, unless evaporated to dryness: alkalies decomposed it. Ferroprussiate of potash gave a dark brown-green precipitate. When more oxide was added, the excess, or a portion of it, combined with the submuriate already formed, and the acid and oxide were totally precipitated, forming another but an insoluble submuriate. Even the addition of muriatic acid caused a partial decomposition of the soluble submuriate, and a precipitation occurred: this happens with no other binary salt. Being analysed, the soluble submuriate gave 37 muriatic acid and 382 of peroxide of iron, equal to one atom of muriatic acid and 9 of peroxide. Mr. Phillips is inclined to consider 1: 10 as the true proportion. Except the subacetate of lead, this is the only subsalt so largely soluble in water; probably, the only one which contains so small an atomic proportion of acid; the only one decomposed by addition of either acid or base: and the last mentioned point shows that there are two other submuriates of iron differing from this one, by insolubility in water. Mr. Phillips has also analysed the submuriate of antimony, or powder of Algaroth. It consists of protoxide of antimony 92.45, muriatic acid 7.8; or 9 atoms and 1. Subnitrate of bismuth was also analysed, and proved to consist of 81.92 oxide of bismuth, and 18.36 nitric acid; or 3 atoms and 1. Submuriate, or magistery of bismuth, being analysed, gave 87 oxide of bismuth, and 13.6 muriatic acid; or 3 atoms and 1. Ac * Journ, de Pharm. 1830, p. 1196. cording to Dr. Thomson, the carbonate of bismuth is a triscarbonate, similar in constitution to the subnitrate and submuriate above. Upon decomposing the subnitrate and submuriate of bismuth by alkali, they yield oxide of bismuth; that, in the first case, is always yellow, but in the second it varies much in colour, being frequently greyish-black and even deep bluish-black. The cause of these variations has not been discovered, nor even the circumstances which ensure a dark coloured preparation. It is not due to sulphuretted hydrogen or other impurities, nor to difference of composition. When the black oxide was heated on platina foil, it lost neither weight nor colour; but, being melted, it became yellow: the cause is probably, therefore, in some difference of aggregation; and may in that respect be analogous to the differences of colour, which can be induced, by various means, on chloride of silver *. 17. ON THE REACTION OF PERSALTS OF IRON AND NEUTRAL CARBONATES. M. Soubeiran has experimentally investigated this action, and arrived at the following conclusions:-i. When salts of the peroxide of iron are decomposed by neutral carbonates, they yield a carbonate of the peroxide equally neutral: this carbonate is soon destroyed to produce a double salt, formed of the neutral alkaline sulphate and the subsulphate of iron: this new salt is also easily decomposed, and yields a new sulphate of iron heretofore unknown, and containing thrice as much base as the neutral salt: a feeble alkali in excess precipitates another subsalt, which chemists have not before noticed, and which is a true double salt, composed of the subsulphate of iron and hydrated oxide of iron. ii. That the aperient saffron of Mars is a hydrate of the peroxide of iron, containing 3 atoms of water mixed with variable and accidental quantities of sesqui-subcarbonate of iron, and sometimes neutral carbonate of iron †. 18. ON THE RELATIVE ACTION OF DILUTED SULPHURIC ACID AND ZINC. (M. A. de la Rive.) Whilst engaged in experiments on the construction of the voltaic pile, M. de la Rive was struck more particularly with a fact which has often been observed by chemists, but has never received its proper explanation. If zinc, purified by distillation, be plunged into dilute sulphuric acid, it is scarcely attacked, especially at first; it produces but a small quantity of bubbles of hydrogen, and these succeed each other very slowly; but zinc of commerce, placed in the same circumstances, produces an enormous quantity of hydrogen, with an effervescence and vivacity well known to those who have prepared this gas. * Phil. Mag. N. S. viii. p. 406. + Journ, de Pharm. 1830, p. 535. In examining the influential circumstances of this action, two appeared to have predominating power; the degree of dilution of the acid, and the state of the metal. These were estimated by the quantity of gas evolved from given surfaces of zinc in a given time; and a convenient little apparatus for that purpose was used, which allowed of the quick repetition of the experiments, and furnished accurate results as to the volumes of gas produced. Six mixtures of acid and water were used. In the following table, the first column gives the number by which any mixture is distinguished in the future experiments, the second expresses the specific gravity, and the third the quantity of sulphuric acid per cent. When the different kinds of zinc were immersed in these acids, it was with the exposure of certain measured and equal surfaces: thus, in the following table, pieces of zinc, each having 200 square millemetres of surface, were left in the respective acid, until each had evolved 300 cubic millemetres of hydrogen gas; and the time occupied, which constitutes the table, of course expresses inversely the facility with which the acid and zinc evolved gas. Acid No. 1. No. 2. No. 3. No. 4. No. 5. No. 6. Zinc of commerce 0'.6" 0'.3" 0'.2" 0'.3" 0'.4" 0.'9" Distilled zinc 3.30" 1.50" 0.30" 0'.26" 0'.24" 1.'30" These experiments were all made with liquid at the same temperature-i. e., between 10° and 12° C., but the temperature rose, and the more the stronger the action; thus, with the acid No. 3 it rose about 5° C., or 9° F., in 15 minutes. Another fact to be noticed is, that the action was very slow in all at first, but afterwards rose slowly with the pure zinc, but rapidly with that of commerce: the latter generally attained its maximum action in 10 minutes, the former required several hours for that effect. It appears, also, that the acid No. 3 is that which acts most energetically upon ordinary zinc; the Nos. 2, 4, and 5 differ somewhat from it; Nos. 1 and 6 much. No. 3 contains 30 per cent. of sulphuric acid; and it may be said generally that, for the evolution of hydrogen most rapidly from ordinary zine, the diluted acid should contain not less than 25, nor more than 50 per cent. of oil of vitriol. The action of the acids on pure zinc, it may be observed, does not follow the same order as on ordinary zinc. With regard to the cause of the difference between pure and ordinary zinc, it might at first be supposed to be due to a degree of openness or porosity in the latter, but it was found that each had the same specific gravity, namely 7.2, and the differences were the same also, when each were reduced to filings. Concluding, therefore, that it was more probably due to the presence of heterogeneous substances in the ordinary zinc, certain mixtures were made of pure zinc and other metals, and four alloys prepared; the first, contained a tenth of iron filings, added when the distilled zinc was in fusion; the second, a tenth of tin; the third, a tenth of lead; and the fourth, a tenth of copper. These zincs were then tried as the former were, the same quantities of surface being exposed and of gas collected. The following are the results :— No. 1, 10° C. No. 2, 10° C. No. 3, 15° C. Acid Distilled zinc 3'.27" 1.50" 0.30" ETTI Lead zinc Common zinc 0'.12" 0'.4" to 6 0'.4". 0'.9" 0'.6" 0.'3" 0'.3" 0.10" 0.3" to 4 0.2" to 1 0.2" to 1. Generally in these experiments the action was at first slow, and then increased more or less rapidly, according to the nature of the alloy, until it had obtained its maximum, which is the rate expressed usually by the time in the table; the copper zinc formed an exception -its action was most rapid at first, and gradually became slower, from the formation of a black crust of oxide, &c. upon it; this being removed, the rapidity of action was restored. The iron zinc, it may be observed, was acted upon as rapidly as the ordinary zinc of com merce. The circumstances accompanying the phenomena in question are such as to induce a persuasion on the mind that the whole is due to electro-chemical action. The first circumstance is the powerful influence of a heterogeneous metal, mixed with pure zinc, to facilitate the decomposition of water and disengage hydrogen. The second is, that the diluted acid which is most powerful in exciting this action is that which is the best conductor of electricity. By a very careful set of experiments, made with the galvanometer, it was found that the acids 3 and 4, and especially 3, were much better conductors than any other of the mixtures. Former experiments had shown that concentrated sulphuric acid was a worse conductor than diluted; but now it was proved that acid, containing between 30 and 50 per cent. of oil of vitriol, was a better conductor than if either stronger or weaker; and it is precisely such acid which evolves hydrogen most rapidly from ordinary zinc. As a further illustration of the influence of voltaic action on zinc dissolving in acid,—if a piece of distilled zinc be dissolved in the diluted acid, it requires a certain time to produce a certain quantity of gas; if a platina wire, immersed in the acid, be made to touch the zinc, it, of course, immediately gives out hydrogen; and the whole quantity of gas from the two metals, under these circumstances, is twice or thrice what it was before. If the platina wire be rolled round the zinc, or if the latter be studded with pieces of platina, then the quantity of gas evolved principally from the platina is much more than from the zinc alone. Now, the action upon the alloyed zinc appears to be quite analogous to the action upon the voltaic circle formed above by the zinc and platina. The small chemical action which takes place on pure zinc determines an electric current between each molecule of zinc, and the molecule of other metal in contact with it. These currents decompose the water which they traverse, according to the well-known laws of voltaic decomposition-evolving the hydrogen upon the heterogeneous molecule, which is negative in all the alloys and combinations mentioned, and carrying the oxygen to the zinc, which is positive, and, combining with it, it forms first an oxide and then a sulphate, which dissolves. This decomposition of water, and consequently the quantity of hydrogen evolved, will be greater as the minute currents of electricity are stronger, and these will be stronger as the acid increases in conducting power. Now it has been found experimentally that the acid mixture which conducts best, evolves most gas in a given time. The decomposition of water should, in this mode of viewing the question, also increase with the difference between the oxidability of the zinc and the other metal. The iron zinc has, however, in these experiments, surpassed the copper zinc, although the two latter metals form a more powerful voltaic arrangement; but then two circumstances affect the result. The energy of the current depends much upon the facility with which it can pass from the negative metal to the fluid in contact; and it has been ascertained that this passage takes place to the acid from the iron, much more readily than from the copper. On the other hand, the copper zinc exerts always a stronger action at first than afterwards-stronger, indeed, sometimes than iron zinc; but then the intensity of its voltaic action causes decomposition of part of the zinc salt in solution, oxide is deposited upon the particles of copper, and, forming the crust before spoken of, diminishes very importantly its voltaic action. The same effect occurs with distilled zinc, furnished with platina wires. From all these considerations, there appears to be no reason to doubt that the striking difference between pure zinc and zinc of commerce, when put into dilute sulphuric acid, is due to the presence of heterogeneous substances in the latter. By analysis, ordinary zinc is usually found to contain traces of copper, tin, lead, and rather more than a hundredth of iron; and, on extending the experiments with the zinc alloys, it was found that 2 per cent. of iron filings, added to distilled zinc, was sufficient to render it as active in acid as ordinary zinc. The elevation of temperature resulting from the chemical action of the liquid upon these zincs, and which increases with the vivacity of the action, is very probably due to the heating power of these numerous electric currents. These currents are more powerful when most gas is disengaged; the heating power of the voltaic current is well |