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ON PURIFYING THE AIR OF APARTMENTS. On the Continent, where every thing is regulated by the governments, and where boards of public health and public education watch withasort of divine prescience over both the bodies and souls of the animated clods which cannot take care of themselves, the subject of this paper is reduced to a regular science or art, and is as regularly treated of in books as mathematics or mineralogy. Our readers need not on this account be under any fear for us, as we hold to the simple rule, that to promote a free circulation of air is the best means of keeping our apartments healthy. At the same time, it does happen, that the windows of a sick chamber cannot be always opened, or the wards of an hospital exposed to a draught, and then a chemical means of purifying the air may be both gratifying to the senses of the patient, and contribute to his recovery. If chemistry had done nothing else for man than explain the manner in which his breathing vititttses the air, and then shewn him how the vitiating substances were to he,gpd Tid of, and the air again rendered pure and health-giving",

she would have conferred on him an incalculable benefit. But for this discovery, it may he doubted if many of the arts which are now practised, could ever have been carried on, and certainly could only have been so at a great expense of human life, and, what is worse, at a great expense of suffering. To give an example of this, which is perhaps not so well known to our readers :—It had long been observed and regretted, that those who worked at gilding by means of the amalgam of mercury and gold, were subject," from inhaling the vapour of the mercury, to a particular disease, which deprived them of the use of their limbs. Mr. Raviro, a large manufacturer of gilded bronze, living at Paris, who had witnessed through his whole life the sad ell'eets of this on his workmen, bequeathed a sum of 3000 francs as a reward to any person who should find out a means of guaranteeing gilders from the insalubrious ell'eets of the mercurial exhalations. This circumstance directed the attention of M. Darcet, a French chemist of considerable eminence, to the subject, and he succeeded, by promoting a circulation of air through a large funnel in one direction, to carry off all the vapours, mercurial and others, of the shop, and convey them above the tops of the houses, so that they were rendered perfectly innocuous. He has now shown the success of his plan in more than a dozen workshops, and the Prefect of police at Paris, has, in consequence, given orders to allow of no new gilding establishment unless it is fitted up according to M. Darcet's method. Thus has this gentleman, by attending to the principles of chemistry, been able to protect a large class of workmen from disease, to ensure them a longer period of existence, and to make that period more pleasurable and free from pain.

In the function of respiration, oxygen gas is inhaled, and about an equal quantity of carbonic acid gas exhaled; and a constant renewal of the former gas, that it may be inhaled, and a removal or; dispersion of the latter, that it may not be inhaled, is necessary for our existence. Independent of this, it has lately been shown, by Dr. Edwards, that azotic gas is also constantly absorbed, and as constantly given out. To provide for this destruction of vital air, a current or draught of fresh air seems the only certain remedy. But independent of this, mephitic gases, as they are called, which exhale from marshes, which are generated in crowded apartments, and supposed to be the active agents in spreading contagious diseases, are known by their effects to be frequently present without that proportion of vital air being diminished which is necessary to existence, or without any chemical test which we know of being capable of detecting them In fact, 'numerous experiments have been made on the air of hospitals, in which contagious fevers were raging, and on the miasma of marshes, without succeeding in detecting any thing beyond the usual' ingredients of atmospherical air. As in general the noxious ingre-' dients arise from exhalations from the body, there is some reason to

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crowded with people, and where," respiration is somewhat impeded^ the vapour will speedily condense on the whole of its surface, arioj(i may be easily collected in a bblfle," placed below the balloon ^ and we . are told if this water be cork,e'd up^ and exposed to a temperature oC'{ 78« Fahr., it will speedily run into putrefactive fermentation, and the'J bottle, on being opened, will ex-"j hale a very fetid odour., At the . same time, if the air which cdn-'1 tains this vapour be analyzed, ijtj! will be found not deficient & tw£nl' . tieth part of oxygen, arid nothing'" deleterious will be detected in it,'.', Experience has, however,,, shown,., that air loaded with these sdr't of' putrefactive vapours is very nox.- , ious, and similar vapours are pro?'1 bably the cause of death by marsh miasma, and of the contagion of

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fevers. On this supposition, we.v see the utility of heat, artificial' heat, however, which disperses tiiijj" vapour wherever, it is applied in '.

destroying, as it is suppose the cause of contagion; *

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Under the idea that impure air was air deprived of its relative quantity of oxygen gas, and under the influence of some other theore? tical ideas of the causes of air being unhealthy, various methods have been proposed of adding to the purity of the air. It has been found that acetic acid is very beneficial; and as its odour is also very grateful, it is customary to convert it into vapour, under the idea that this destroys contagious iair, by plunging a red hot iron into a sufficient quantity. On board bur ships of war, where the men are so crowded together that precautions; of this description are indispensible, vinegar is used for this purpose in large quantities; and our plate represents the machine employed as better than plunging the iron into the liquid, to convert the liquid into vapour. It consists of a lamp and an earthen dish, placed in a japanned tin cylindrical vessel—a precaution which is necessary on board ship, where, in fact, they are suspended when used. It has a little tube, for carrying oft' the smoke of the lamp. The earthen dish serves the purpose of a sand-bath, and a glass cup, containing the vinegar, is. placed in if, Fig. 1 is a representation of the apparatus ready for use; Fig. 3 is the earthen vessel and glass cup employed; and Fig. 3 shows the instrument dismounted. A variety of other substances besides vinegar have been employed for the same purpose; and Dr. Carmichael Smith received a reward of 50001. from, the government for his method of purifying the air of ships and hospitals by the fumes oi' nitric acid gas.^ The French chemist, M. Gj}fon Morveau, proposed muriatic gas for the same purpose; but we believe nothing is so effectual as promoting the circulation of atmospherical air. This subject is, however, now so well understood, that the air of a a well-re-, gulated hospital, or of a wellordered ship, is as pure and as free from offensive smells as the air of any ordinary apartment.

CHEMISTRY AS A SCIENCE. Art. XVII.

BISMUTH. MERCURY.

The first of these is a metal very sparingly diffused, of not much value, and of little use. Its ores are found chiefly in Germany, and are a compound of the metal and either sulphur or oxygen. It is also found native. To procure the metal from the ores, they are exposed in shallow pits to heat in contact with fuel. The metallic matter which collects at the bottom is then mixed with an equal weight of black flux, is put into a crucible and covered, to about the depth of an inch, with common salt. A strong heat is applied, the mixture fuses, and the metal, known by the name of bismuth, collects at the bottom of the pot. It is of ayellowish or reddish white colour, little subject to change in the air. It is somewhat harder than lead, and softer than copper, and scarcely malleable, rather breaking to pieces than spreading out when struck with the. hammer. It melts at 480» Fahrenheit; at a still higher temperature it burns, and forms an oxide cal ed flowers of bismuth. This nclal was not at all known to the ancients, but the Germans became acquainted with it in the 16th century. It was supposed to be silver in a growing state, and not yet arrived at perfection; it was also classed as a species of lead; but at length it was decided that it is a peculiar metal,and the attempts since made to reduce it to any other elements have failed. Bismuth is employed with alloys of other metals to make printers' types; it also enters into the composition of some pewters. It has the remarkable property of making other metals fusible, and' hence it is used for making solder. An alloy, composed by fusing together bismuth eight parts, lead live, and tin three, will melt at the temperature of boiling water, which affords an opportunity of putting a joke on those who are ignorant of this circumstance. This alloy is i formed into spoons, which look exactly like pewter; but to the surprise

in one direction, to carry off all the vapours, mercurial and others, of the shop, and convey them above the tops of the houses, so that they were rendered perfectly innocuous. He has now shown the success of his plan in more than a dozen workshops, and the Prefect of police at Paris, has, in consequence, given orders to allow of no new gilding establishment unless it is fitted up accordingto M. Darcet's method. Thus has this gentleman, by attending to the principles of chemistry, been able to protect a large class of workmen from disease, to ensure them a longer period of existence, and to make that period more pleasurable and free from pain.

In the function of respiration, oxygen gas is inhaled, and about an equal quantity of carbouio acid gas exhaled; and a constant renewal of the former gas, that it may be inhaled, and a removal or dispersion of the latter, that it may not be inhaled, is necessary for our existence. Independent of this, it has lately been shown, by Dr. Edwards, that azotic gas is also constantly absorbed, and as constantly given out. To provide for this destruction of vitalair, a current or draught of fresh air seems the only certain remedy. But independent of this, mephitic gases, as they are called, which exhale from marshes, which are generated in-crowded apartments, and supposed to be the active agents in spreading contagious diseases, are known by their effects to be frequently present without that proportion of vital air being diminished which is necessary to existence, or without any chemical test which we know of being capable of detecting them In' fact, 'numerous experiments have beon made on the air of hospitals, in which contagious fevers were raging, and on the miasma of marshes, without succeeding in detecting any thing beyond the usual' ingredients of atmospherical air. As in general the noxious ingre-" dients arise from exhalations from the body, there is some reason to

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crowded with people, and where,' respiration is somewhat impeded, the vapour will speedily condense' on the whole of its surface, anq., may be easily collected in a .bottle' placed below the balloon ^ and w'p , are told if this water be corked up and exposed to a temperature o£, 78« Fahr.,it will speedily run into putrefactive fermentation, and fhej bottle, on being opened, will ex-'j hale a very fetid odour.. At ujfl' same time, if the air which cdn-'J tains this vapour be analyzed^ it.. will be found not deficient a tw£n,^ tieth part of oxygen, aria nothing^' deleterious will be detected in it.'! Experience has, however,, shownj., that air loaded with these sort of' i putrefactive vapours is very np^- \ ious, and similar vapours are pro- . bably the cause of death by marsh miasma, and of the contagion of fevers. On this supposition, we J see the utility of heat, artificial heat, however, which disperse^ this vapour wherever.it is applied in '] destroying,asjt is supposed to do," the cause of contagion; l

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Under the id$a that impure air was air deprived of its relative quantity of oxygen gas, and under the influence of some other theorer tical ideas of the causes of air being unhealthy, various methods have been proposed of adding to the purity of the air. It has been found that acetic acid is very beneficial; and as its odour is also very grateful, it is customary to convert it into vapour, under the idea that this destroys contagious air, by plunging a red hot iron into a sufficient quantity. On board pnr ships of war, where the men are so crowded together that precautions of this description are indispensible, vinegar is used for this purpose in large quantities; and our plate represents the machine employed as better than plunging the iron into the liquid, to convert the liquid into vapour. It consists of a lamp and an earthen di.sh, placed ina japanned tin cylindrical vessel—a precaution which is necessary on board ship, where, in fact, they are suspended when used. It has a little tube, for carrying off. the smoke of the lamp. T^e earthen dish serves the purpose of a sand-bath, and a glass cojgj containing the vinegar, is, plaped in it, Fig. 1 is a representation pf the apparatus ready for ujt'e';. Fig. 2 is the earthen vessel and glass cup employed; and, Fig, i$ snows the instrument dismounted. A variety of other substances besides vinegar have been employed for the same purpose; and Dr.Carmichael Smith, received a reward of 50001. from, the1.government for his method of purifying the air of ships and hospitals by the fumes of nitric acid gas. The French chemist, M. G.»y(on Mor.veau, proposed muriatic gas for the same purpose; but we believe nothing is so effectual as prompting the circulation of atmospherical air. This subject is, however, now so well understood, that the air of a a well-re-, gulated hospital, or of a wellordered ship, is as pure and as free from offensive smells as the air of any ordinary apartment.,'" .,,,., ,

CHEMISTRY AS A SCIENCE. Art. XVII.

BISMUTH. MERCURY.

The first of these is a metal very sparingly diffused, of not much value, and of little use. Its ores are found chiefly in Germany, and are a compound of the metal and either sulphur or oxygen. It is also found native. To procure the metal from the ores, they are exposed in shallow pits to heat in contact with fuel. The metallic matter which collects at the bottom is then mixed with an equal weight of black flux, is put into a crucible and covered, to about the depth of au inch, with common salt. A strong heat is applied, the mixture fuses, and the metal, known by the name of bismuth, collects at the bottom of the pot. Itisof ayellowish or reddish white colour, little subject to change in the air. It is somewhat harder than lead, and softer than copper, and scarcely malleable, rather breaking to pieces than spreading out when struck with the hammer. It melts at 480° Fahrenheit; at a still higher temperature it burns, and forms an oxide cal ed flowers of bismuth. This netal was not at all known to the ancients, but the Germans became acquainted with it in the 16th century. It was supposed to be silver in a growing state, and not jet arrived at perfection; it was also classed as a species of lead; but at length it was decided that it is a peculiar metal, and the attempts since made to reduce it to any other elements have failed. Bismuth is employed with alloys of other metals to make printers' types; it also enters into the composition of some pewters. It has the remarkable property of making other metals fusible, and' hence it is used for making solder. An alloy, composed by fusing together bismuth eight parts, lead live, and tin three, will melt at the temperature of boiling water, which affords an opportunity of putting a joke on those who are ignorant of this circumstance. This alloy is formed into spoons, which look exactly like pewter; but to the surprise

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