crystallize in our laboratories. Thus (Brewster's Journal, vol. x.) Repetti observed quartz in a pasty state and in the act of crystalling. The same kind of occurrence is said to have been observed of various other substances, as beryl, opal, heavy spar." Report of the First and Second Meetings of the British Association, p. 374-379. DIRECT DEMONSTRATION OF THE RULE FOR THE MULTIPLICATION OF NEGATIVE SIGNS. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, No direct proof, that I am aware of, has ever been given of the rule for the multiplication of negative signs, although proofs by Euler and a hundred authors have been given by reductio ad absurdum. You will oblige me by an insertion of the following direct proof, especially as I have heard it disputed whether a direct demonstration is practicable, and since it will take up but a very small portion of your admirable periodical. I remain, &c. J. O. H. A direct Demonstration of the Rule for the Multiplication of Negative Signs. This rule may be proved by the assistance of the following proposition: The product of a negative quantity into any other quantity is equal to minus the product of the first quantity without the negative sign, and the other quantity. The product of a negative quantity into any other quantity signifies that that negative quantity is to be added or subtracted as many times as there are units in that other quantity, accordingly as this other quantity is positive or negative, and consequently the result will be the same as if the negative quantity were positive, and the negative sign added to the result. Let the quantities to be multiplied bea and +b. Then and (− a)x(+b) = − ( + a) x (+b) = − ab - (− a)x(—b) = − ( + a) x ( − b) = − (− a b) = +ab. Q. E. D. ON THE SOLUBILITY OF CARBONATE OF LIME, ETC. IN HYDROCHLORATE OF AMMONIA. M. Vogel, in the following notice, which is of the greatest importance in the analysis of many inorganic substances, remarks, that in analytical researches, particularly in those which are for the purpose of discovering the elements which enter into the composition of a mineral, confidence has hitherto been placed in the statement, that amongst the bases which are precipitated by the alkalies or their carbonates, magnesia was entirely redissolved by the addition of a solution of hydrochlorate of ammonia, and that this method has been generally used to separate this substance from other bases, such as lime, alumina, &c. &c. It is a well-known fact that hydrochlorate of ammonia has the property of dissolving with facility many insoluble or diffi cultly soluble bodies; this is the case with tartrate of lime, chloride of silver, and the recently precipitated carbonates of nickel and zinc, &c: but one that is much less known is, that recently precipitated carbonate of lime does not wholly resist the solvent power of this salt, which is likely to cause error, and lead us to imagine that lime is magnesia in analyses, particularly when the first occurs only in minute quantities. Thus when a solution of sulphate of lime is decomposed by an alkaline carbonate, the precipitated carbonate of lime easily redissolves in a solution of hydrochlorate of ammonia. Again, when very dilute solutions of chloride of calcium and nitrate of lime are decomposed by an excess of carbonate of potash, so as to leave no traces of lime in the supernatant liquid, by the addition of a concentrated solution of this ammoniacal salt the precipitate entirely disappears. These clear solutions of carbonate of lime in hydrochlorate of ammonia become turbid by exposure to the air, and a portion of carbonate of lime is again deposited; but there always remains a certain quantity dissolved which cannot be precipitated even by boiling the clear solution. If precipitated carbonate of lime is washed with a sufficient quantity of water, it does not dissolve, after a lapse of twenty-four hours, so easily in the ammoniacal salt as when just precipitated; and even if the precipitate is not washed, but suffered to remain in the liquid from which it has been precipitated, its solubility in hydrochlorate of ammonia, although not prevented, is considerably diminished. Even the natural compact varieties of carbonate of lime, and the minerals into which it enters, do not completely resist the solvent power of this salt of ammonia. Calcareous spar or Carrara marble finely powdered, and merely shaken for a few minutes with a solution of this salt, affords a solution, which contains, after filtration, a notable portion of lime. This solubility of carbonate of lime in hydrochlorate of ammonia is, however, very much less than that of carbonate of magnesia. Carbonate of barytes recently precipitated from a dilute solution of the chloride of barium by carbonate of potash, disappears on the addition of a solution of hydrochlorate of ammonia. This is also partially the case when native carbonate of barytes, in powder, is mixed with a solution of the ammoniacal salt and then filtered by evaporation of the liquor, a residue is obtained which contains some chloride of barium. The solvent power of sal ammoniac is equally exerted on recently precipitated carbonate of strontia. When carbonate of magnesia has been dried at the temperature of boiling water, it becomes much more difficult, and takes a much longer time, to dissolve in the ammoniacal solution than when recently precipitated. The concentrated solution of carbonate of magnesia in hydrochlorate of ammonia becomes turbid by exposure to air, but does not deposit any magnesia by ebullition. At first sight it may seem singular that the earthy carbonates before mentioned should lose their solubility in hydrochlorate of ammonia; but this may be explained by admitting that by repose they acquire a greater degree of cohesion, and approach the crystalline state, which would naturally diminish their solubility. To conclude the preceding experiments show, 1st, that the solubility of an earthy carbonate in hydrochlorate of ammonia will not authorize us to conclude that the precipitate is magnesia; 2nd, that freshly precipitated carbonate of lime, and also both marble and calcareous spar, are dissolved by this salt; 3rd, that carbonate of barytes recently precipitated, and also witherite and carbonate of strontia, are likewise dissolved by this agent; 4th, and lastly, that the solution of the above-mentioned earthy carbonates affords, by its decomposition, carbonate of ammonia and a chloride of the base.L'Institut, Sept. 28, 1836, and Jour. für Prackt. Chimie, No. 7, 1836. Note. The importance of the above notice of M. Vogel, in the analysis of those earthy minerals, in the course of which the earth is precipitated from a hydrochloric solution by carbonate of ammonia, has reminded me of some unfinished and hitherto neglected experiments which were made in the early part of this year, on the mutual action of hydrochlorate of ammonia and the carbonates of lime, barytes, and strontia; and as these lead to exactly the same conclusion as that at which M. Vogel has arrived, viz. the mutual decomposition of hydrochlorate of ammonia and the earthy carbonates, I am now induced to notice them, as they tend to confirm a fact which must so greatly affect the analysis of many minerals, especially those containing magnesia. One equivalent, or 54 grains, of hydrochlorate of ammonia was dissolved in a few ounces of distilled water, and to this solution was added an equivalent, or 98 grains, of perfectly dry carbonate of barytes, obtained by precipitating a solution of the chloride of barium by one of sesquicarbonate of ammonia; this mixture was then boiled for about four hours, occasionally renewing the water which had been evaporated. During the ebullition, particularly at the commencement, carbonate of ammonia was disengaged, and at the expiration of four hours a perfectly clear solution was procured, consisting of chloride of barium and a trace of hydrochlorate of ammonia, but without the slightest trace of carbonic acid. Equivalents of precipitated carbonate of strontia, 74 grains, and hydrochlorate of ammonia, 54 grains, treated in the same manner, were boiled for eight hours: long before the expiration of this time the vapour had ceased to exhibit the slightest traces of carbonate of ammonia; the solution filtered left 3:34 grains of carbonate of strontia undecomposed; the solution, consisting of chloride of strontium, when boiled with caustic soda, did not afford the slightest indication of ammonia; it is therefore most probable that the whole of the hydrochlorate of ammonia in this experiment was decomposed. Equivalents of carbonate of lime (precipitated) and hydrochlorate of ammonia, boiled together for eight hours, left 97 grains of carbonate of lime, and the solution, when treated with soda, afforded traces of ammonia. These experiments not only confirm M. Vogel's conclusion, but they also show that, by an elevation of temperature, the mutual decomposing power of these bodies is materially increased; and it must now be a question whether at comparatively low temperatures, 32° of Fahr., for instance, this power is, or is not, completely suspended. This winter, if opportunity offers, a few experiments shall be made to determine this point, and their results, if of any interest, noticed. J. DENHAM SMITH. METHOD OF DETECTING SULPHUROUS ACID IN THE HYDROCHLORIC ACID OF COMMERCE. This process is founded on the action that protochloride of tin exerts on sulphurous acid. Pelletier, sen., noticed (Ann. de Chimie, tome xii. page 231, 1792,) that when solutions of these substances are mixed, the salt of tin deoxidizes the sulphurous acid, and affords a beautiful yellow precipitate, consisting of sulphur and peroxide of tin. The mode of proceeding is as follows: Put about half an ounce of the hydrochloric acid which is to be tested into a glass, and then add about a quarter of an ounce of the salt of tin, such as is very white and not altered by exposure to the air: stir these together, and then add about two or three times its bulk of distilled water, and mix well. When the hydrochloric acid does not contain sulphurous acid, no particular action ensues on the addition of the chloride of tin and the water; the salt of tin dissolves, and the solution is merely rendered slightly turbid by the action of the air. But should the hydrochloric acid contain sulphurous acid, it will be seen, that on the addition of the salt of tin, the acid becomes turbid and yellow, and then, on adding the distilled water, the odour of hydrosulphuric acid will be easily distinguished, the liquid will bebecome of a brown tint, and deposit a powder of the same colour. These phænomena are so distinct that we cannot hesitate for an instant as to the presence or absence of sulphurous acid. Sometimes the brown colour is not developed until after the lapse of a few minutes, and the larger the proportion of sulphurous acid the darker is the shade produced. The disengagement of hydrosulphuric acid occurs at the time the mixture is diluted with water; by standing, the liquor deposits a yellowish brown powder, consisting of sulphuret and peroxide of tin. The reason of this curious reaction is easily explained. One portion of the salt of tin is converted into perchloride at the expense of another portion of this compound, and the tin set free from this decomposition acts on the sulphurous acid so as to produce at the same time both peroxide and protosulphuret of tin. The hydrosulphuric acid which is disengaged immediately after the addition of the water is owing to the hydrochloric acid acting on a part of the sulphuret of tin; chloride of tin is again formed, and hydrosulphuric acid gas liberated. To obtain the phænomena described it is necessary to add the salt of tin to the hydrochloric acid before the addition of the water, for if we commence by diluting the acid, the addition of the salt does not produce any discolouration. This test is one of such delicacy and accuracy that M. Girardin, the author, assures us that it will detect a one hundredth part of sulphurous acid in a sample of hydrochloric acid.— Ann. de Chim. et de Phys., March 1836. ON PLATINA. BY J. W. DÖBEREINER. When native platina is fused with twice its weight of pure zinc, this alloy, after cooling, pulverizes; and put into moderately dilute sulphuric acid until the action has ceased, and then heated with very dilute nitric acid, assisted by heat, a residue is obtained which, after washing with water, consists of undissolved iridium, osmium, and, in silver coloured grains, a heavy blackish-grey powder, composed of platinum, palladium, iridium, rhodium, and osmium. This compound metallic powder possesses the same properties as the platina separated from its alloy of potassium or iron, which J. W. Döbereiner has examined and frequently described. It absorbs and condenses oxygen gas, and is such an oxidizing agent, that it not only converts the oxalic and formic acids into carbonic acid, and alcohol first into acetal, next into aldehyd, and then into acetic acid, but also converts the contained osmium into osmic acid, which sublimes at a gentle heat, or can be dissolved out by an alkaline solution. In the latter case the oxidizing properties of this metallic powder are still increased, and a preparation obtained which not only suddenly ignites hydrogen gas, but also the vapours of pyroxylic spirit and alcohol, and detonates when heated on platina foil, a property Descotils pointed out fifty-five years ago, but which has not been since noticed." This powder is dissolved in aqua regia nearly as easily as gold. Muriatic acid destroys its property of absorbing oxygen gas; so that it ceases to detonate on heating, or to act metallically (metalylisch, or as Berzelius calls it, catalylisch,) on the above substances: however, by heating it with a solution of a fixed alkali, its former power is restored.-Poggendorff's Annals. 6. Hazy, METEOROLOGICAL OBSERVATIONS FOR OCTOBER 1836. Chiswick.-Oct. 1, 2. Stormy with rain. 3. Heavy rain: boisterous: clear and frosty at night. 4. Frosty: fine. 5. Hazy very fine. with rain. 7. Overcast: rain. 8. Dense clouds: rain at night. 9. Clear and fine. 10. Heavy rain. 11-13. Boisterous. 14. Fine. 15. Showery. 16-18. Foggy. 19. Very fine. 20-26. Foggy in the mornings: fine. 27. Showery clear and cold. 28. Cloudy and very cold: north-west wind. 29. Snow. 30. Clear: snow yet remaining on the ground. frost fine. The depth of snow on the morning of the 29th was nearly three inches; and during the day there were stormy showers of snow in very broad flakes. Notwithstanding the bright sunshine on the following day, the snow generally still continued to cover the ground. 31. Sharp Boston.-Oct. 1. Rain. 2. Cloudy. s. Rain. 4, 5. Fine. 6. Fine: 7. Fine. 8. Cloudy. 9. Fine: rain early A.M. rain P.M. 16. Fine. 12. Fine. 10. Rain. 13, 14. Cloudy. 17. Cloudy. 18. Cloudy: 24. Foggy. 11. Stormy: very stormy night rain early A.M. 25. Cloudy. 28. Fine: ice this 30. Fine hail-storm early A.M. 31. Fine great deal of snow on the ground. Our Correspondent Mr. Veall adds the following note: : I am in possession of journals of the weather kept at Boston during the last twenty years, but do not find such a fall of snow recorded in the month of October." |
