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potass together in equal parts, after trituration it most abundantly; and, in order to obtain it by in a porcelain mortar. This fluid has an acid, the cheapest and easiest process, he recommends astringent taste, and the name iodous acid has that we should submit this fucus, dried and re been given to it; but the proportion of its ele- duced to powder, to distillation with sulphuric ments has not been ascertained. Quarterly Jour- acid. nal of Science and Art, xvii. 381.

339. In the Addenda to Dr. Henry's Elements, 335. Chloriodic acid, or as it is called by Gay we meet with the following additional notification Lussac chlorure of iodine, is obtained by the di- in reference to the source &c. of iodine: “The rect action of chlorine upon iodine, jodine ab- only known sources of iodine were certain vegesorbing less than one-third of its weight of chlo- tables and some marine molluscæ, till Vauquelin rine; the union produces crystals of a deep discovered it a few months since in the specimen orange color. Gay Lussac states indeed that two of a mineral, sent from Mexico, under the name compounds are the result of this combination, of Virgin silver from Serpentine.' The best the one, as noticed, of a deep orange color, the method of separating the iodine from this subother an orange red, the largest portion of chlo- stance was found to be as follows: Five parts of rine being contained in the first.

the pulverised mineral were heated with two 336. Chloriodic acid precipitates the salts of parts of caustic potassa, and a little water to iron and other metals.

facilitate the mixture; and kept some time in 337. Nature of Iodine (From Dr. Henry's fusion. The mass was washed with water till Elements). Iodine, from all that we yet know the latter ceased to become alkaline; a portion respecting it, is to be considered as a simple or of the liquor saturated with nitric acid has the elementary body, having a very striking analogy property of rendering starch blue, when a few with chlorine, which it resembles, firstly, in form- drops of solution of chlorine had been previously ing one acid by uniting with hydrogen, and a added. Of the portion insoluble by water, diludifferent acid with oxygen; secondly, in its ted nitric acid dissolved a part with effervescence; effects on vegetable colors; thirdly, in its affording but there remained a yellowish substance resemwith the fixed alkalis, salts, which nearly ap- bling chloride of silver, which became orange proach in character to chlorates ; and fourthly, colored by heat, and passed to a greenish yellow in its electrical habits. Its discovery indeed lends on cooling. This substance was iodine of silver. strong support to that theory which considers 340. The alkaline liquor afforded hydriodate chlorine as a simple body, and muriatic acid as of potassa, by saturating the alkali with sulphuric a compound of chlorine and hydrogen. In the acid, evaporating to dryness, and adding alcohol, property of forming an acid, whether it be united which took up the hydriodate only, leaving the with hydrogen or oxygen, iodine bears also sulphate of potassa. The whole iodine thus exan analogy to sulphur; and it is remarked by tracted from 100 grains of the ore, Vauquelin Gay Lussac of the combinations of chlorine, calculates at 18} grains; and on reviewing the iodine, and sulphur, with the elements of water, composition of the ore, the other ingredients of that while the acids which they respectively form which were sulphur, lead and silver, he considers with oxygen have their elements strongly con- it as most probable that all the iodine contained densed, those formed with hydrogen have their in the native mineral was united with the latter elements very feebly united. Sulphur has the metal. It is probable that with this clue to more strongest affinity for oxygen, then iodine, and perfect analysis, iodine will be found in othe lastly chlorine. But for hydrogen, chlorine has minerals, and especially in ores of silver, foi a stronger attraction than iodine, and iodine than which metal it has like chlorine a strong attracsulphur ; whence it appears that the affinity of tion. Ann. de Chym. et de Phys. xxix. 991. each of those bodies for oxygen is inversely pro- 341. FLUORINE. This is a principle which portionate to its affinity for hydrogen.

has not hitherto been obtained in a separate state; 338. The source of iodine in nature has been it seems to be united with hydrogen in the fluoric investigated by M. Gaultier de Claubry. His acid; this acid, like the muriatic, appears to be first experiments were directed to the several composed of hydrogen, and a peculiar base, varieties of fucus, the combustion of which fur- which base in the instance before us, has been nishes the soda of sea-weeds. Before these vege- denominated Auorine by Sir H. Davy; and phtore tables are destroyed by combustion he ascertained from peoplos, destructive, by Ampére : it possesses that iodine exists in them, in the state of hydri- a negative electric energy, which is proved by its odate of potassa ; and that calcination only de- being determined to the positive pole. stroys the vegetable matter with which it is com- 342. It exists in the fluor spar, a mineral found bined.

As the bydriodate of potassa is a deli- in great beauty and abundance in Derbyshire. quescent salt, it remains in the mother liquor This spar is stated to be composed of twenty after separating the carbonate of soda, and most calcium, and 17:1 fuorine. See FLUORIC Acid. of the other salts, by crystallisation. In the 343. ELECTRO-POSITIVE BODIES.-The bodies course of these experiments M. De Claubry found which fall now to be considered have been usually that starch is one of the most delicate tests of the classed as inflammable or combustible; to this presence of iodine, and if added to any liquid appellation, Dr. Henry very properly states, that containing it, with a few drops of sulphuric acid, the same objection exists as to that of supporters iodine is indicated by a blue color of greater or of combustion. Against our author's own clasless intensity. In this way he detected iodine in sification, it may, however, be objected that the the decoction

several varieties of fucus; but title of electro-positive includes all substances he was unable to discover the slightest trace of with the exception of the few just noticed. Dr. it in sea-water. The fucus saccharinus yielded Henry, indeed, anticipates this objection, and


proposes a subordinate division of elementary 349. For the properties and peculiarities of bodies, that is of those bodies which have not hydrogen gas, we refer to the article Air; but hitherto been resolved into a more simple we may quote in this place an illustration which

is given in Dr. Henry's work, of the fact that 344. i. Those which by combining with elastic fluids or gases penetrate each other, and oxygen, chlorine,or hydrogen, are capable of being become thoroughly mixed under all circumconverted into acids, but wbich have no me- stances; in this, differing from common or intallic properties.

elastic fluids (liquids) wh are capable of a re345. ii. Those which either decidedly rank maining in contact with each other for a long as metals, or are so nearly allied to metals in time without admixture. their general habitudes, as to render it improper 320. • Provide twa glass vials, each of the cato assign to them any other place in a chemical pacity of about an ounce measure, and also a arrangement. In the class of metals will be tube open at both ends, ten inches long, and found a few bodies which yield acids when united 1-20th inch bore. At each end the tube is to be with oxygen ; and one or two which are even passed through a perforated cork, adapted to the acidified by combination with hydrogen.

necks of the vials. Fill one of the bottles with 346. One great advantage, as it appears to us, hydrogen gas, and the other with oxygen gas; in adopting this arrangement, is, as above-inti- place the latter on a table with its mouth upmated, that it preserves in the student's mind a wards; and into this insert the tube secured by constant recollection of the great principles of its cork. Then holding the hydrogen bottle with electro-chemical science, and of the immense its mouth downwards, fit it upon the cork at the benefit these new views have already conferred on top of the tube. The two bottles thus connected, chemistry, and still promise to confer.

are to be suffered to remain in this perpendicular 347. In Mr. Brande's Manual, which cannot be position. After standing two or three hours, too bighly recommended to the student, the fol- separate the vials and apply a lighted taper to lowing substances are introduced for considera- their mouths, when it will almost certainly oction in his division, under the title of Simple casion an explosion in both. The hydrogen gas, Acidifiable and Inflammable Substances; and though sixteen times lighter than the oxygen, he prefaces the notice of them by stating that the must, therefore, have descended through the tube bodies belonging to this class are electro-positive, from the upper into the lower vial; and the and consequently, when separated from their com- oxygen gas, contrary to what might have been binations with the substances described in the last expected from its greater weight, must have aschapter, (oxygen, chlorine, iodine), by Voltaic scended through the tube, and displaced the electricity; they are attracted by the negative lighter hydrogen.' surface. With very few exceptions they com- 351. Hydrogen and Orygen. (Water.)-Mix bine with the three supporters of combustion two volumes of hydrogen gas with one volume already described, and of these compounds one of oxygen gas, and inflame the mixture by the or more are acids. They are six in number. electric spark in a proper apparatus; the gases 1. Ilydrogen. 2. Nitrogen. 3. Sulphur. 4. Phos- will by this treatment disappear totally, and the płorus. 5. Carbon. 6. Boron. The plan that inner surface of the vessel will be moistened we are about to pursue will lead to the investi- with a fluid which will be found to be pure gation of these bodies and principles, almost in water, and equal in weight to the gases which the direct order, thus adopted by Mr. Brande. have disappeared. They are all acidifiable, but not all in strict pro- 352. Again, expose pure water to the action priety combustible or inflammable bodies. of Voltaic electricity, and you resolve it into

348. HYDROGEN. See Air, p. 381.-Hy- hydrogen, which will be disengaged at the negadrogeo exists in a state of gas, or, in other words, tive pole, and oxygen will be disengaged at the it is combined with caloric, and probably with positive pole; the hydrogen will be two volumes, electricity and light, to such an extent as to oc- the oxygen one, so that water is demonstrated casion its gaseous constitution, and from this both by synthesis and analysis to be formed of combination we cannot separate it any other hydrogen and oxygen, in the proportion of two othe way than by causing it to combine with volumes of the former to one of the latter. some other substance. This gas was first atten- 353. Under the word Water, in the body of tively examined by Mr. Cavendish; it was for- the work, we shall enter into a disquisition on its merly termed inflammable air. It may be prepared properties; it may be here generally stated, that by the action of dilute sulphuric acid upon iron in its ordinary and natural state, such as spring filings or upon zinc. The gas will escape, and and river water, it always contains air, and that may be collected in the usual inamner. Mr. Do- it is always so far combined with foreign subnovan has proposed, in order to purify the gas stances as considerably to interfere with its abfrom admixture with sulphuretted hydrogen stract existence. The water immediately from and carbonic, that we should first agitate common rain is purer, but even this always contains some hydrogen with lime water during a few minutes; of the atmospherical elements, and also some next with a little nitrous acid ; afterwards with a traces of vegetable or animal matter. solution of green sulphate of iron, and finally after water has been distilled, some impurities or with water.

Dr. Henry, in alluding to this pro- particles of foreign matter remain in it, and to posal, says it appears to him that the carbonic render it completely free from these impregnaacid, and sulphuretted hydrogen, may equally tions, it requires to be slowly and carefully rewell be removed by the simple process of washing distilled. More or less of water is ever conthe crude gas, either with lime-water or with a tained in the air of the atmosphere, even in the solution of caustic potassa.

dryest weather, and many bodies, from mere ex



posure to the atmosphere, will abstract a portion for the purpose, but to use the materials that of it, or in other words of its moisture; such have the power of furnishing the acid gas, as the are the deliquescent salts mentioned under chloride of sodium (common salt), oxide of the nead of crystallisation. Whether aqueous manganese, and sulphuric acid. fluids exist in the atmosphere chemically com- 359. On the theories which have prevailed bined, or merely mechanically mixed, has been respecting Chlorine and Muriatic Acid.-As made a question; or rather, it has been debated these bave an important bearing upon the lewhether it is chemical solution or mere calorific gitimacy of the new electro-chemical doctrines, influence which retains that portion of fluid in we shall take the liberty of extracting verbatim, the air which is capable of being deposited by the account of them, found in Dr. Henry's an alteration of circumstances; it is most con- volumes, • There are few subjects,' says sistent with the general analogy of material ex. Dr. Henry, 'respecting which the opinions of istence, perhaps, to suppose the latter to be the chemists have undergone such frequent changes

as concerning the nature of chlorine and of 354. M. Thenard has shown that an additional muriatic acid. The views originally taken by quantity of oxygen may be made to unite with Scheele, the illustrious discoverer of the former water, so as to constitute a very different pro- substance, was that the muriatic acid is comportion of hydrogen and oxygen in composition, pounded of a certain base, and an imaginary than the proportion of water. This combination principle called phlogiston (see part 1st.); and is effected by means of the peroxide of barium, that by the action of certain bodies it became a substance afterwards to be described. See dephlogisticated, or deprived of that supposed Quarterly Journal of Science and Art, vol. viii. principle of inflammability. It was afterwards p. 114, 115.

found, however, that all bodies which are capa355. Hydrogen with Chlorine, Muriatic Acid, ble of producing this change in muriatic acid or, more consistently with the new theory and contain oxygen, and that their portion of oxygen nomenclature, Hydro-chloric Acid.—Mix 'equal is diminished by the process. It appeared, quantities of hydrogen and chlorine, and expuse therefore, to be an obvious conclusion, that what. them to the action of a lighted taper, or even to takes place in the action of metallic 'oxides on the direct action of the sun's rays, an explosion muriatic acid, is simply the transference of or detonation will take place; the same effect oxygen from the oxide to muriatic acid; and, will be produced by Voltaic electricity, showing, conformably with this theory, the resulting gas says Mr. Brande, a curious analogy between received the name of oxygenated muriatic, or electric and solar light; for ordinary artificial oxymuriatic acid. Sir H. Davy was led by his light does not accelerate the combination (see early experiments to modify in some degree this Brande's account in the Philosophical Transac- view of the theory of the process ; and to contions of 1820). The produce of the union of sider the muriatic acid as a compound of a cerequal parts of chlorine, whether effected sud- tain basis with water; and the oxymuriatic acid denly and with explosion, or silently, is muriatic, as a compound of the same basis with oxyger. or more properly speaking, hydrochloric acid gas. This modification was rendered necessary by the

356. This acid is procurable by other methods; fact, that when a metallic body is heated in muriatic it may be obtained by pouring sulphuric acid on gas, oxymuriatic acid is obtained, and water apcommon salt, the sulphuric acid unites in this pears in a separate state. It was evident, therecase with the base of the salt, and the muriatic fore, that muriatic acid gas must either contaia acid is evolved in the form of gas.

water ready formed, or the elements of water, 357. Muriatic acid gas has a pungent smell, or hydrogen capable of composing water wich it is caustic in its action upon the skin, it es- the oxygen of the oxide. But at a subsequent tinguishes flame, it is heavier than common air. period, the same distinguished philosopher vas Its specific gravity is stated by Gay Lussac to induced by the experiments of Gay Lussac and be 1.278; 100 cubic inches, according to Mr. Thenard, as well as by his own researches, 10 Brande, weigh 38.8 grains. It is very rapidly form a different theory on the subject. Oxyabsorbed by water, and, when dissolved in that muriatic acid he now considers as a simple or fluid, it forms the liquid muriatic acid, for the undecompounded substance; and muriatic acid mode of preparing which, and for the theory of as a compound of that simple substance with its formation, see HYDROCHLORIC Acid.

hydrogen. To convert the muriatic acid into 358. This acid in a liquid state manifests the chlorine we have only, according to this view, following properties. It emits suffocating to abstract hydrogen from the muriatic acid, and whitish fumes, it affords muriatic gas by being this, it is believed, is all that is effected by the heated with heat. When diluted with water action of those oxides which are adapted to the an elevation of temperature is occasioned ; it purpose. Again, to convert chlorine into mucombines freely with the alkalis and with most riatic acid, we have only to combine i; with of the earths, both in their caustic, or rather pure, hydrogen; and accordingly, the simple mixture and their carbonated states. It is specifically of one measure of each of these gases, when ex

When brought into contact posed for a short time to the sun's rays, or exwith any substance containing oxygen in a state ploded by an electric spark, affords two measures of loose combination, its hydrogen unites with of muriatic acid gas. this oxygen, forming water, while the chlorine 360. The oxymuriatic acid, or chlorine, as Sir becomes liberated in the state of gas. Indeed H. Davy proposes to call it, in order to avoid chlorine is procured in this way, but it is usual all connexion of its name with hypothetical not to employ the already formed liquid acid views, is supposed also lo unite at once with

heavier than water.



40 24
60 36

100 60

the metals, without requiring, like the sulphuric, Davy, in the 34th volume of Nicholson's Journitric, and other acids, that the metals should nal; to Sir H. Davy's paper, in the Philosofirst be in the state of oxides. In proof of this phical Transactions for 1818, p. 169; to the theory it appears to be sufficiently established, 8th vol. of Transactions of the Royal Society of that no oxygen can be obtained either alone, or Edinburgh; the Annals of Philosophy, 12th in a state of combination with combustible vol. 379, and xiii. 26, 285; and to a paper by bodies added for the purpose, from the com- Mr. R. Phillips in the new series of that work, pounds of chlorine and metals. The analyses, vol. 1st, p. 27, on the action of chlorides on however, of the metallic muriates, as they were water.' Henry. formerly considered, remain unimpeached by 363. Hydrogen and Iodine.-When iodine is this change of theory. All that is necessary to presented to nascent hydrogen,a union is produced transmute in ideas a muriate, into a compound of and a gaseous acid is the result, which is named chlorine, is to deduct the oxygen from the me- hydriodic acid. This gas is best prepared in tallic oxide; and adding to it the muriatic acid, any quantity, by the action of moistened iodine, to consider the same as chlorine. For example, upon phosphorus. It is received over mercury, muriate of soda, deprived of all water, con- but, as it is soon decomposed by that metal, it sists,

should be transferred as soon as possible into On the old theory, of muriatic acid 467 28 an exhausted vessel.

364. This acid is colorless, and has an exSoda composed of Oxygen 13:3} 53.3 32 tremely sour taste; it smells like muriatic acid. Sodium 40.0 S

Its specific gravity, as compared with hydrogen, is given as 59.3 to 1; 100 cubic inches weighing

133.6 grains. On the old theory, chloride of sodium consists of

365. In a liquid form it is best procured by Sodium

passing sulphuretted hydrogen through a mixChlorine.

ture of iodine and water; sulphur becomes deposited, and, on heating and filtering the liquor,

we obtain a pure solution of hydriodic acid. On the discarded theory of oxymuriatic acid,

366. This liquid acid is slowly decomposed that supposed compound was stated to be con- by the action of atmospheric air, its hydrogen stituted of three volumes of muriatic acid gas, + is attracted by the oxygen of the air, and a por1 volume of oxygen condensed into 2 volumes, tion of iodine is thereby rendered free, which and by weight of

colors the liquor. It is likewise decomposed

by concentrated sulphuric, by nitric acid, and Oxygen Muriatic acid

by chlorine. Voltaic electricity rapidly decomposes the liquid acid, iodine appearing at the positive, and hydrogen at the negative pole.

Although the acid gas so powerfully acts upon 361. According to this view, the atom of dry mercury, the liquid acid does not affect it. inuriatic acid (hydrogen being unity, and oxygen Those bodies called oxides, in which the oxygen 8), would be equivalent to 28; and this + 8 is loosely combined, readily decompose the (1 atom of oxygen), would give 36 for the atom acid, and neutral salts are obtained, called hyof oxymuriatic acid. The latter number, in- Criodates; a process of preparing the hydriodate deed, still represents the atom of chlorine as de- of potass, is given in the new series of the Anduced from the fact, that it unites with an equal nals of Philosophy, vol. vii. p. 48. We menvolume of hydrogen gas, and is 36 times speci- tion this on account of the salt having lately been fically heavier than that inflammable gas. "We employed as an important article in medicine. may consider then, 60 parts of common salt as See MEDICINE. composed, according to the old view, of 28 367. Hydrogen with Fluorine (Fluoric parts dry muriatic acid, and 32 parts of soda, acid).—This is introduced here under the pre(= 24 sodium and 8 oxygen), or of 24 sodium sumption that hydrogen is its acidifying princi+ 36 chlorine, according to the new theory. ple; "there appears,' says Dr. Henry, every

362. It is remarkable, that there is hardly any reason to believe, that hydrogen is the acidifying fact connected with the chemical history of principle of fuoric acid, and that, in the same chlorine and muriatic acid, that does not admit manner as hydrochloric acid is constituted of of being almost as well explained upon the hy- chlorine united with hydrogen, this acid also pothesis that chlorine is compound, as upon consists of a peculiar base, belonging, like chlothat of its being a simple substance. On the rine, to the electro-negative class of bodies, whole, however, the weight of evidence is very and rendered acid by combination with hydromuch in favor of the new, or rather the revived gen.' To this basis, though not yet exhibited in opinion of its elementary nature, especially since a separate state, the name of fluorine has been the discovery of jodine; and I have little scruple, given, and the acid has been termed hydrotherefore, in adopting it, as affording the most fluoric. simple and satisfactory explanation of pheno- 368. This acid may be procured in a liquid mena, as well as the best ground-work for a state, by distilling the powdered fluor spar,

with conspicuous arrangement of the objects of che- twice its weight of strong sulphuric acid. Mr. mistry. The reader who wishes to examine Knight, in the seventeenth volume of the Philofully the evidence for both opinions, is referred sophical Magazine, has described and repreto the controversy between Dr. Murray and J. sented an ingenious apparatus for the purpose.

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369. One peculiarity of tne fluoric acid is, hitherto without success, to discover the ingrethat it acts strongly on glass ; hence it has been dients of which nitrogen is composed, supposing employed for etchings on glass. This peculia- it to be a compound body. Sir H. Davy ignited, rity makes it of course necessary to preserve it by means of intense electricity, potassium in niin bottles, coinposed of materials which the acid trogen gas, and hydrogen appeared as the result, has not power thus to corrode, those of silver or some nitrogen being at the same time found lead may be used.

deficient. Hence it was supposed that the ni370. Fluorine, it will be recollected, is at trogen had suffered some decomposition, but present rather a supposed than an actually de- in further experiments it was ascertained that monstrated base. The fluates are still treated

n proportion to the potassium being free froic of by some chemists as compounds of fuoric a coating of potassa, which contains water, in acid with metallic oxides; but Sir H. Davy that proportion, was less hydrogen found to and M. Ampére, as we have already stated, con- appear, and less nitrogen was also observed to sider them as compounds of metals, with a be wanting. peculiar principle analogous to chlorides, which 374. Nitrogen and Orygen.-Besides the prohas been called Muorine or phtore. “Fluor spar, portion of nitrogen with oxygen that forms at for example, may be either a fuate of lime, or mospheric air, and for an account of which we a fluoride of calcium. And in the same manner refer to the article Air, these bodies are known that we convert, in imaginati a muriate into to unite in four other proportions, and constitute a chloride, we may change a fluate into a fu- the compounds called, oride. Thus Auor spar may be constituted i. Nitrous oxide of Davy, or the protoxide of either of


ii. Nitric oxide, or deutoxide of nitrogen. 1 atom of fuoric acid

ii. Nitrous acid. 1 atom of lime {

iv. Nitric acid. | 8 oxygen

375. Nitrous Oxide.-The salt called nitrate

of ammonia will yield this gas, by being heated Weight of the atom of anhydrous ? ftuate of lime ..

38 in a retort to a temperature of between 420 and

430°. It may be collected over water. The Or it may consist of 1 atom of fuorine, 10 + 8

theory of its formation is as follows: nitric acid 18

is made up of oxygen and nitrous gas, as we 1 atom of calcium

shall shortly state; the component parts of amWeight of the atom of fuoride of calcium

monia are hydrogen and nitrogen. By an increase

of temperature, the nitrous gas combines with 371. It should be added, that if the latter an additional dose of nitrogen, and thus nitrous views be correct, fluates, like muriates, can only oxide is formed; the oxygen of the decomposed be capable of existing either in solution, or in a nitric acid unites with the hydrogen of the amstate of hydrous salts. The actual conversion monia, and forms water. of a fuoride into a fluate will then be attended 376. Nitrous oxide gas has the following chawith the decomposition of an atom of water; racteristics : it is heavier than common air, 100 and 1 of hydrogen by weight will unite with 18 cubic inches weighing, according to Brande, fluorine, making the real atomic weight of Huoric 46•125 grains; compared with hydrogen, its acid 19, while 8 of oxygen will unite with the specific gravity is 20:5 to 1. Its taste is sweet, atom of metallic base. The atomic weight of and its smell not disagreeable. It is easily abthe Auate will, in that case, be 19 + that of the sorbed by water. It supports combustion, and alkaline, or earthy base, or 9 (= to an atom of a taper immersed in it burns brilliantly, somewater) more than the number assigned to the times with a crackling noise. Red-hot charcoal anhydrous compound.' Henry.

burns in it with brilliancy, and consumes some 372. NITROGEN, OR Azote (see the article Air, of its oxygen. Many of the metals likewise p. 380, No. 56,-Nitrogens, or azote, (the latter decompose it at a high temperature. This gas word derived from the Greek à and Zwn, on account detona'es with hydrogen, and the best analysis of the unfitness of the gas for supporting animal of it is effected in this manner : one volume of life), was first recognised as a distinct aeriform nitrous oxide requires one volume of hydrogen. fuid in 1772. In addition to the modes of pro- This mixture, fired by the electric spark, procuring it, as stated under Air, we may give the duces water, and one volume of nitrogen remains. following: fill a bottle about one-fourth with the Now, as one volume of hydrogen takes half a solution of nitrous gas, in liquid sulphate of volume of oxygen to form water, nitrous oxide iron, or with liquid sulphate of lime, and agitate must consist of two volumes of nitrogen and one it with the air that fills the rest of the bottle. volume of oxygen; these three volumes being so During the agitation the thumb must be firmly condensed, in consequence of chemical union, placed over the mouth of the bottle, and when as only to fill the space of two volumes. The removed the mouth of the bottle must be im- specific gravity of nitrogen, compared with mersed in a cup-full of the same solution, which oxygen, is as 13 to 15. Nitrous oxide therefore will supply the place of the absorbed air. The consists of agitation and admission of Auid must be re

13 Nitrogen newed alternately, so long as any absorption

7.5 Oxygen takes place.

373. Various attempts have been made, but Number for nitrous oxide


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