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antiquary, and keeper of the Pontifi- the Monumenti Gabini, the descripcal Museum. Young Visconti shew- tion of the Villa Borghese, and other ed early the talents which afterwards works of equal merit. When the 80 much distinguished him ; his child. French carried off these monuments hood was spent in decyphering in- of art to Paris, they removed Visconti scriptions, explaining medals, and de- along with them, and he was appointscribing monuments. An exhibition ed Keeper of the Museum. During of this knowledge, made at the age of his stay in France, he contributed twelve, before an assembly of cardi- most valuable accounts of the antiques nals, excited the utmost astonishment. contained in the Musée Francois and He reached maturity at the moment Musée Royal. His last work, which when the successful researches of promised to prove the greatest, was his Winckelman, Lanzi, and other learn- Greek and Roman Iconography, one ed men, had opened a wide field of of the most remarkable works of the antiquarian inquiry. “A man, how- age, both for its magnificence in point ever,” says Rochette, “ was still want- of art, and for the original and curious ing who should collect the scattered information contained in it. Only one discoveries, and should unite in him- volume in folio appeared before the self all the different species of science, lamented death of the author. Benecessary to fix our knowledge of the sides his works, his learned contempoancients and their arts on a solid ba- raries peculiarly valued him for the sis.” Such a man was Visconti, who, ready and sure information to be obin his description of the Museum Pio- tained from him upon every subject. clementinum, erected a monument, “ It was not,” says one of them, “ a which will always do honour to his learned man that we consulted; it was memory. Texts, medals, inscriptions, a book always open ; a sort of library statues, basso-relievos, are all admira- open to all the world." His opinion bly classed, and made to illustrate an- bore almost the authority of an ancient religious and political institu- cient. In this view it was anxiously tions, and mythological traditions. sought by the English government, The highest degree of enthusiasm for in its investigation of the value of the these pursuits was combined in him Elgin marbles. M. Visconti left a with solid judgment and deliberate widow, with two children, and only a inquiry. He published afterwards moderate inheritance.

CHAPTER III.

VIEW OF IMPROVEMENTS IN SCIENCE DURING THE YEAR.

Oxygenation of Acids and of Water.-Constitution and Analysis of Mineral Waters.— Impressions of Cold from the Higher Atmosphere, and the New Instrument called the Ælhrioscope.-Operations for determining the Figure of the Earth.

OXYGENATION OF ACIDS AND OF equal complication if all the steps of WATER.

manipulation, by which the ultimate One of the most interesting trains products are obtained from the subof research in experimental chemistry stances in their natural and crude that have recently appeared, is that of state, were reported to us for the first the indefatigable chemist, Thenard, time. These have become easy in on the oxygenation of the acids consequence of certain steps being aland of water. The final result is ready familiar to us, or certain interthe obtaining of oxygenated water, mediate products being well known. or, a deutoxide of hydrogen, as the This is not exactly the case in the preatomic chemists denominate it, from sent instance; and, therefore, though the idea, that in a state of purity with those whose chemical knowledge this compound has a double pro- was acquired some years ago it reportion of oxygen (compared to the quires more care to reach the concluhydrogen) that water or the protox- sion, it is to be recollected that each ide has. The leading instrument by of the intermediate steps is to be which he was enabled to accomplish considered as a separate discovery, this combination was the peroxide of and that the greater time and attenbarium; and, as the process is some- tion demanded for the ultimate object what long, and apparently complica- is rewarded with the knowledge of a ted, we shall describe its different series of scientific acquisitions, all of stages in a regular and deliberate them elegant. This series may be manner. It is thought complicated, divided into these distinct stages :chiefly because several of its steps I. The obtaining of barytic earth, or depend on comparatively recent dis- pure barytes.-II. From this the obcoveries, all of which require to be taining of the peroxide of barium.well understood ; but many of those III. The oxygenation of different facts in chemistry which are reckon- acids; and, IV. The oxygenation of ed plainer and easier would present water.

1. Barytes is obtained from the about 4lbs. troy. When this is made heavy spar, found to be a sulphate moderately red-hot, a current of oxyof barytes, which is for this purpose genous gas is past over it by squeezpounded, mixed with charcoal, and ing a bladder which is filled with that subjected for a length of time to an gas, and tied over one of the cool ends intense heat. The acid is decomposed of the tube. If an empty bladder is by the charcoal, and its radical, the tied over the opposite end, that porsulphur, combines with the barytic tion of the gas which does not comearth to form a sulphuret of barytes. bine with the barytes passes into it, This is treated with nitric acid, which and by compressing this in its turn, combines with the barytes to form a the current is passed and repassed till liquid nitrate of barytes, and from the whole is combined, which is done which crystals of that barytic salt are with extreme facility. When the tube obtained by evaporation. For the is cooled, the contents are to be taken purpose of procuring this salt in a out. These are now a greyish white very pure state, and, above all, free PEROXIDE OF BARIUM, and must be from any iron or manganese, it should kept in an accurately closed bottle. be again dissolved in water, a small III. The peroxide of barium thus excess of barytic water added, and the obtained, is soluble in various liquid solution filtrated, and then crystal- acids—the nitric, phosphoric, andmulized. The pure nitrate thus ob- riatic. It is first moistened with a tained must be decomposed by heat, little water, which makes it fall to extract the barytes. This must be readily into a powder, without much done, not in an earthenware retort, increase of temperature. This powder because this contains both iron and may be added by degrees to the manganese, but in a retort of fine nitric or muriatic acid, and is by white porcelain. If four or five them quickly dissolved, forming lie pounds of the nitrate are thus treated, quid nitrate, or muriate, of the perthe operation should last three hours, oxide of barium. If the barytes is after which BARYTES remains. It is now precipitated, a liquid combinacombined with some silex and alu- tion of the acid with oxygen will be mine, from the fusion with the retort, obtained. Such precipitation is efbut free from iron and manganese, fected by adding sulphuric acid in which is an essential circumstance. the requisite quantities. Sulphate

II. The pure barytes thus obtained of barytes is formed, and a copihas been found, by galvanic analysis, ous precipitate of this compound is to consist of a peculiar metal, in com- separated, the superabundant oxy. bination with oxygen. The metal is gen remaining in combination with called barium. This metal is found the liquid acid. After one quantity to have the property of combining of the barytes has been thus sepawith a larger proportion of oxygen rated from the solution by being conthan that which forms this earth. It verted into a sulphate, and one dose now forms a peroxide of barium. The of oxygen has been left in combinaformation of the peroxide is accom- tion with the acid, more of the perplished by exposing the pure earth to oxide may be added, from which the oxygenous gas, underan elevated tem- barytes may be in like manner preciperature. The barytes is cut into pitated, and an additional dose of pieces about the size of the end of the oxygen made to combine with the finger, is put into a luted glass tube, acid. The operation may be several long and wide enough to contain times repeated, as often at least as spheric pressure.

seven, without the loss of any oxygen. The oxygenation of sulphuric acid Afterwards the impregnation with is not obtained with equal simplicity. qaygen may be rendered successive- When that acid is brought into conly stronger, by further repetitions tact with the peroxide of barium, it of the process, but a little oxy- forms sulphate of barytes by combingen is now lost. These oxygenated ing with the barytes, which is the proacids cannot well be concentrated by toxide of barium, and the overplus of beat

, as heat has the effect of separa- oxygen is disengaged in the gaseous ting the oxygen ; but they may be form, exactly in the same way as this concentrated by evaporation under acid operates on the black oxide (or an exhausted receiver, containing peroxide) of manganese, combining quicklime, or some other hygrome- with an inferior oxide of that metal, tric substance, to absorb the moisture and setting oxygenous gas at liberty. evolved by the removal of the atmo- In order to effect the oxygenation of

The oxygenated the sulphuric acid, we first procure nitric acid thus obtained does not, an oxygenated muriatic acid, which like the nitro

muriatic acid, act on should be kept in a glass surrounded gold; but it readily dissolves those with ice. We must also be provided metals which simple nitric acid is with a solution of sulphate of silver. capable of dissolving, and the solu- This solution is to be added drop by tion takes place without the disen- drop to the oxygenated muriatic gagementof oxygenous gas, and with- acid. (It is absolutely necessary that out the production of heat. When the sulphate should not contain any muriatic acid is treated in the same uncombined oxide of silver.) An inmanner, a liquid is obtained possess- stant decomposition takes place. The ed of properties wholly different from muriatic acid quits the liquid state those of chlorine, the substance so and the oxygen to combine with the long known under the name of oxy- oxide of silver ; thus producing that muriatic acid. It does not, like chlo- very insoluble salt, the muriate of rine, dissolve gold and platinum. It silver. In the meantime, the sulphuis very acid, colourless, and almost ric acid being disengaged, becomes destitute of smell. A boiling heat liquid, and combines with the oxygen converts it into oxygenous gas and which the muriatic acid had quitted, muriatic acid. These experiments and we thus have oxygenated sulare considered by some chemists as phuric acid. This, which is turbid Betting at rest the question of the while the sulphate is adding, becomes nature of chlorine, and proving it to limpid the moment that the whole of be wholly different from a combina- the muriatic acid is combined with oxtion of muriatic acid with oxygen. ide of silver. It is equally important, on M. Thenard has frequently given the the other hand, that no excess of sulacid as many as 125 volumes of oxy- phate of silver should be added begenous gas. The oxygenated acid dis- yond what is required to engage the solves zinc without effervescence, the muriatic acid. Alternate trials must oxygen in combination with the acid be made with the tests of nitrate of being taken up by the metal to form silver on the one hand, and muriatic an oxyd, in preference to the oxygen acid on the other, on single drops of the water

, which, with the simple taken from the whole liquid, till the liquid muriatic acid, takes place, oc- point of saturation is exactly hit; the casioning an effervescence by the liquid is then to be filtered, the filter evolution of hydrogen gas.

itself pressed through cloth, and the turbid drops which it yields passed to the experiment of Professor Leslie. through paper, and added to the rest. (See our former volume, p. 262.) In We have now a liquid composed sole- this situation a part of the water is ly of oxygen WATER, AND SULPHU. evaporated, while none of the oxyRIC ACID.

gen is disengaged. This is a fact IV. From the liquid compound which we should not have anticipated, now mentioned we have to separate knowing that the oxygen is easily the sulphuric acid, and then we shall separated by heat. It shews that the have oxygenated water. For this oxygen is not kept in its state of conpurpose we treat it with an aqueous densation, in any degree, by the pressolution of barytes, i.e. barytic water. sure of the atmosphere. A low temThe barytes and the sulphuric acid perature, however, has a great influare now precipitated in mutual com- ence on the stability of the compound. bination, and THE OXYGEN REMAINS By keeping the oxygenated water a IN UNION WITH THE WATER. An- sufficient length of time under such other plan, and one which renders the a receiver-for example two days, oxygenation of the water less dilute the liquid remaining will sometimes in the first instance, is to put the contain two hundred and fifty times liquid in a glass mortar surrounded its volume of oxygen. After the conby ice, to rub into it gradually a little centration has been carried to a cercaustic barytes, previously slacked tain pitch, part of the oxygen sepaand ground to powder, till the sul- rates in bubbles, which burst with phuric acid is nearly precipitated, difficulty. The separation of a part (which is known by the liquid hardly of the oxygen, when it takes place, reddening litmus,) then filter the will be ascertained by the rising of liquid, and complete the separation the mercury in the mercurial gage of the sulphuric acid by adding a few of the air-pump. An earlier disendrops of barytic water.

gagement of it is sometimes occaIt is expedient at first to have a sioned by the presence of foreign slight excess of barytes in the liquid, matter, and is stopped by adding two that any trace of iron or manganese or three drops of very weak sulphuric which may have escaped the former acid. operations may now be separated, The highest point of concentration after which a few drops of very dilute to which the author has brought the sulphuric acid will remove the excess liquid is that of containing 475 times of barytes ; and the operator should its volume of gas, at a medium temso manage as rather to leave a slight perature and pressure. The proporexcess of acid than of base, as the acid tion is ascertained by introducing a tends to fix the oxygen, but the base portion of it previously diluted into to disengage it.

à tube inverted over mercury, and By a repetition of the process passing up a little oxide of manganese now described, on the same quantity diffused in water. The whole osy; of liquid, the proportion of oxygen gen is immediately disengaged, and may be increased. But in order to on comparing its volume with that of concentrate this curious substance the compound before it was diluted, more powerfully, another process is we calculate the proportion expresrequired—that of evaporation under sive of its strength. an exhausted receiver, containing a Oxygenated water is heavier than hygrometric substance, such as

pure water; it sinks in it like sulvessel of strong sulphuric acid or phuric acid, and has the same slugpowdered muriate of lime, according gish consistence. The property which

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