for the Mathematical Sciences; le Chevalier Cuvier, Perpetual Secretary for the Physical Sciences. V. Fermentation. Gay-Lussac conceives that during fermentation sugar is converted into nearly equal weights of alcohol and carbonic acid. His reasoning is as follows: sugar, he conceives, is composed by weight of 0.4 carbon and 0.6 water, or of Let us triple all the elements of sugar to render the quantity of hydrogen the same in both, it will then be 3 volumes vapour of carbon 3 volumes of hydrogen & volumes of oxygen. It is obvious that in order to convert sugar into alcohol we must withdraw I volume of the vapour of carbon 1 volume of oxygen gas, which, by combining, form 1 volume of carbonic acid. If we reduce these volumes to weights, we find that 100 parts of sugar are converted by fermentation into 51.34 alcohol and 48.66 carbonic acid. (See Annales de Chimie, xcv. 317. VI. Composition of Gum Tragacanth. According to Bucholz, gum tragacanth is composed of Gum 57 43 100 The jelly is the substance which makes tragacanth swell when it is put into water. The gum is soluble in cold water, but not the jelly; but the jelly dissolves in boiling water, and then loses the property of gelatinizing. 1 VII. Method of obtaining pure Sulphate of Manganese. I am not sure that Fischer's mode of obtaining this salt in a state of purity is known to British chemists. On that account I shall state it here; because it is easy, and by far the cheapest mode with which I am acquainted. Take one part of green sulphate of iron and four parts of black oxide of manganese; reduce both to powder, and mix them well together. Then expose the mixture to a red heat in a crucible. The dry mass, when digested in water, lets a sulphate of manganese dissolve which is entirely free from iron and copper. Care must be taken that the oxide of manganese employed be free from lime; otherwise the quantity of sulphate of manganese obtained will be small in proportion to the quantity of that earth present. VIII. Native Carbonate of Strontian. Some time ago I dissolved 3 oz. 400 gr., or 1840 gr., of the native carbonate from Strontian, in Argylshire, in nitric acid, and separated the nitrate of strontian by crystallization. After having separated three or four different crops of crystals, there remained behind a mother liquid, from which I could procure no more nitrate of strontian, either by spontaneous crystallization or evaporation. I therefore evaporated the whole to dryness, and digested the dry mass in alcohol. The alcoholic solution being filtered, a white powder remained on the filter, which was nitrate of strontian. On being dissolved in water, and evaporated, it yielded crystals of pure nitrate of strontian to the very last drop. The alcoholic solution was evaporated to dryness, and re-dissolved in water. The colour of the solution was yellowish brown; but the tinge, I conceive, was owing to part of the alcohol having been altered by the heat; for ammonia threw down nothing from the liquid, nor altered its colour. Carbonate of soda threw down 26 grains of carbonate of lime; but the liquid remained as deeply coloured as ever. It appears from this experiment that native carbonate of strontian contains a portion of carbonate of lime, either mixed or in combination. As 1840 grains yielded 26 grains of carbonate of lime, it follows that in the native carbonate of strontian there is contained 1.41 per cent. of carbonate of lime. During the evaporation of the alcoholic solution, a portion of it was accidentally spilled, by a sudden motion of the sand-bath on which it was evaporating. Hence the quantity of carbonate of lime was greater than I found; perhaps it amounts nearly to two per cent. Thus it appears that native carbonate of strontian contains as much carbonate of lime as arragonite does of carbonate of strontian. IX. Weight of an Atom of Strontian. The weight of an atom of strontian which I gave in my table (Annals of Philosophy, vol. ii. p. 46), being founded on experiments made with native carbonate of strontian, cannot be quite correct. I thought it, therefore, proper to make an experiment with artificial carbonate, which I knew to be pure. I dissolved 600 grains of nitrate of strontian in water, and precipitated it by carbonate of soda. The precipitate, after being well washed and dried, weighed 300-8 grains of carbonate of strontian. 100 grains of thi [MAY, carbonate were dissolved with the proper precautions in nitric acid. This experiment was twice repeated. The loss of weight each time was 299 grains. Therefore carbonate of strontian is composed of Carbonic acid ... 29.9 or 1 atom 70.1 or 1 100.0 Hence it follows that an atom of strontian weighs 6'449. I consider this result as agreeing sufficiently with Klaproth's experiments. He found that the native carbonate lost 30 grains when dissolved in an acid. Now as this mineral contains a mixture of carbonate of lime, it ought to lose more weight when dissolved in an acid than pure carbonate of strontian; for carbonate of lime contains 43-2 per cent. of carbonic acid. If we suppose my experiments correct, and native carbonate of strontian to contain 1-4 per cent. of carbonate of lime, it ought, when dissolved in an acid, to lose 30-086 grains in weight. Now this almost agrees with the experiment of Klaproth. The difference does not amount to X. Number of Plants known. part. According to Humboldt, the species of plants at present known amount to 44,000. Of these, 6,000 are cryptogamous; the remaining 38,000 have flowers. The distribution of these 38,000 phanerogamous plants is, according to Humboldt, as follows: The plants described by the Greeks, Romans, and Arabians, scarcely amounted to 1,400. (Humboldt's Nova Genera et Species Plantarum, Prolegomena, p. 11. XI. Verdigris. Hitherto verdigris has been chiefly manufactured in France; but a manufactory of it has lately been established at Deptford, near London. I had the curiosity to examine a portion of this verdigris, that I might be able to compare it with the French, the composition of which was already known to chemists from the experiments of Proust, 100 grains of the verdigris being digested for some time in about a pint of distilled water, the whole was thrown upon a filter. I was surprised at the length of time requisite to allow the liquid portion to pass through the filter. At least a fortnight elapsed before a I was able in this way to separate completely the soluble part of the verdigris from the insoluble. The insoluble portion, being dried in the open air, weighed 54.3 grains of course 457 grains had been dissolved. : The solution consisted entirely of acetate of copper, and was composed of Black oxide of copper 20 12.85 32.85 Hence it is obvious that this portion of acetate of copper in the verdigris was combined with 12.85 grains of water. The insoluble portion, which weighed 54-3 grains, consisted chiefly of subacetate of copper, but contained likewise some carbonate of copper. This carbonate I found could be separated from the subacetate by means of diluted sulphuric acid; for the carbonate is much more soluble in this acid than the subacetate. The analysis made in this way, however, cannot entirely be depended upon, as it somewhat overrates the quantity of carbonate of copper; because the whole dissolved in the sulphuric acid during the effervescence is considered as carbonate, though part of it probably is subacetate. My analysis gave the following quantities: Subacetate of copper ... Carbonate of copper.. By dissolving 100 grains of verdigris in water by means of sulphuric acid, and throwing down the copper from the solution by a cylinder of zinc, I obtained 38 grains of copper very nearly. Mr. Benicke informed me that 14,107 lbs. of copper were converted in his manufactory into 41,830 lbs. of verdigris. Hence the copper in 100 grains of verdigris ought to be only 33.72 lbs. From this it is obvious that the verdigris loses weight by keeping. The portion which I examined had stood for some time wrapped up paper in my laboratory, and probably lost a portion of its weight before I examined it; so that the quantity of water which I found in it, though considerable, was not the whole which it had contained when originally manufactured. French verdigris, according to the analysis of Proust, contains Soluble acetate of copper in XII. Iolite. This is a mineral which was first formed into a peculiar species by Werner. It was afterw de Physique; and Hai eribed by Cordier in the Journal ame of dichroite, because it exhibits one colour when viewed by reflected light, and another when seen by transmitted light. Lucas, in the second volume of his Tableau des Espaces Minerales, proposes to call it cordierite, on the supposition (which is ill founded) that Cordier was the discoverer of it. Karsten gave it the name of iolite, from its violet colour. This mineral has hitherto been found only in the kingdom of Granada, in Spain, in two places. 1. At Granatillo, near Nijar, disseminated in a blue clay contained in green-stone. 2. At the bay of St. Pedro, in what Cordier describes as a lava. Its colour is violet-blue, approaching to black. Its primitive form is a six-sided prism; but it occurs likewise in twelve-sided prisms, and in grains. Fracture sometimes imperfectly foliated, sometimes imperfectly conchoidal. Lustre, vitreous. Sometimes opake; sometimes translucent on the edges. Specific gravity 2.560. Before the blow-pipe it melts, with difficulty, into a greyish-green enamel. It has been lately analyzed by Gmelin, who found its constituents as follows: The mineral from India known by the name of saphir d'eau, which has an indigo-blue colour, and the specific gravity of from 2.555 to 2.670, has likewise been analyzed by Gmelin. He found its constituents as follows: Silica From this analysis it seems to follow that the saphir d'eau is an iolite. XIII. Blue Mineral from Vesuvius. This mineral was first noticed by Breislak, in his Voyages dans la Campanie. Bruun Neergaard considered it as a variety of hauyne (Jour. de Mines, No. 125); and in Lucas's Tableau des Espaces Minerales, vol. ii. p. 226, it is classed under the species hauyne. Its colour is that of ultra-marine, with a shade of grey. Its powder has a light blue colour. |