Dioxide Sentence Examples

Of these carbon dioxide and water are the most prominent.

Humans require relatively little oxygen, and plants are constantly transforming the carbon dioxide we exhale back into useful oxygen.

When sulphur is burned in air or oxygen, sulphur dioxide is produced, which is a powerful disinfectant, used to fumigate rooms which have been occupied by persons suffering from some infectious disease.

Sulphur dioxide and sulphuretted hydrogen are present in volcanic exhalations and in many mineral waters.

Fungal and phanerogamic parasites can make no use of stich substances as carbon dioxide, but draw elaborated products from the bodies of their hosts.

The oxides of type RO are soluble in water, the solution possessing a strongly alkaline reaction and rapidly absorbing carbon dioxide on exposure; they are basic in character and dissolve readily in acids with the formation of the corresponding salts.

It may be obtained from argyrodite by heating the mineral in a current of hydrogen; or by heating the dioxide to redness with carbon.

We can prepare, in the laboratory, a white powder that proves to be calcium carbonate, that is, it appears to be wholly composed of carbon dioxide and lime.

It burns with a pale blue flame, forming sulphur dioxide and water.

We find in nature two other unlike substances, marble and Iceland spar, each of which is wholly composed of carbon dioxide and lime.

Gay-Lussac in 181q, is usually obtained in the form of its barium salt by suspending freshly precipitated hydrated manganese dioxide in water and passing sulphur dioxide into the mixture until all is dissolved; the barium salt is then precipitated by the careful addition of barium hydroxide.

It is only stable in dilute aqueous solution, for on concentration the acid decomposes with formation of sulphuric acid, sulphur dioxide and sulphur.

Membrane oxygenator-The artificial lung that adds oxygen and removes carbon dioxide.

Terrestrial plants have a gaseous interchange of oxygen and carbon dioxide which is necessary for respiration and feeding.

They are accompanied by intercellular channels serving for the conduction of oxygen to, and carbon dioxide from, the living cells in the interior of the wood, which would otherwise be cut off from the means of respiration.

It may lead to an incipient asphyxiation, as the supply of oxygen may be greatly interfered with and the escape of carbon dioxide may be almost stopped.

Now, as the materials which plants absorb are carbon dioxide from the air, and various inorganic compounds from the soil, together with water, it is clear that if this view is correct, vegetable protoplasm must be fed in a very different way from animal, and on very different materials.

Substances contained in the Protoplastn.Starch may be found in the chlorophyll bodies in the form of minute granules as the first visible product of the assimilation of carbon dioxide, and it occurs in large quantities as a reserve food material in the cells of various parts of plants.

Four oxides of sulphur a.re known, namely sulphur dioxide, S02, sulphur trioxide, S03, sulphur sesquioxide, S203, and persulphuric anhydride, S 2 0 7.

The dioxide has been known since the earliest times and is found as a naturally occurring product in the gaseous exhalations of volcanoes and in solution in some volcanic springs.

The sulphites are prepared by the action of sulphur dioxide on the oxides, hydroxides or carbonates of the metals, or by processes of precipitation.

When heated in air, tellurium burns, forming the dioxide Te02.

This is at first colourless carbon dioxide, but later on inflammable gases come out of the mass, which at this stage has turned into a thicker, pasty condition, showing that the end of the reaction is near.

The sulphides can be removed by " oxidizing " them into thiosulphates by means of atmospheric air, with or without the assistance of other agents, such as manganese peroxide; or by " carbonating " them with lime-kiln or other gases containing carbon dioxide; or by precipitating them with lead or zinc oxide.

The same apparatus is used for " oxidizing " by means of atmospheric air passed through by means of an injector; sometimes both air and carbon dioxide are passed in at the same time.

The wet alkali-waste as it comes from the lixiviating vats, is transferred into upright iron cylinders in which it is systematically treated with lime-kiln gases until the whole of the calcium sulphide has been converted into calcium carbonate, the carbon dioxide of the lime-kiln gases being entirely exhausted.

Any sulphuric acid present is removed by baryta water, the precipitated barium sulphate filtered off, the solution acidified by hydrochloric acid and reduced by sulphur dioxide.

Also refers to a respiratory therapy involving deeper and/or faster breathing to keep the carbon dioxide pressure in the blood below normal.

In newborns, ECMO is used to support or replace an infant's undeveloped or failing lungs by providing oxygen and removing carbon dioxide waste products so the lungs can rest.

A pump pushes the blood through an artificial membrane lung, where oxygen is added and carbon dioxide is removed.

Anemia-A lack of hemoglobin, the compound in blood that carries oxygen from the lungs throughout the body and brings waste carbon dioxide from the cells to the lungs, where it is released.

Sunburns may be avoided by the liberal use of a sunscreen containing either an opaque active ingredient such as zinc oxide or titanium dioxide or a nonopaque active ingredient such as PABA (para-aminobenzoic acid) or benzophenone.

Electrolyte levels will be measured along with carbon dioxide and pH and serum osmolality, which may indicate hypertonic dehydration.

Belli's anti-chloasma cream is an oil-free sunscreen containing titanium dioxide and zinc oxide to block UVA and UVB rays.

A stabilized oxygen formula of 28 percent sodium chlorite in distilled water, MMR produces chlorine dioxide when mixed with lemon juice or citric acid.

According to a study found on PubMed, sodium dioxide has been shown to be relatively harmless when used in small amounts, but questions were raised about the possible effects of using larger doses over extended periods of time.

Sodium chlorite and sodium dioxide are listed by the Department of Health and Human Services as toxic substances.

In fact, tips for reducing exposure to sodium chlorite and sodium dioxide are featured.

Other ingredients include potato starch, gelatin, and silicon dioxide.

Chemical vapor deposition is another method to create black or gray diamonds - carbon dioxide is injected into plasma and the resulting crystals may have a black hue.

For example, manufacturing of one kilogram of PET involves releasing 40 grams of hydrocarbons, 25 grams of sulfur oxides, 18 grams of carbon monoxide, 20 grams of nitrogen oxides, and 2.3 kilograms of carbon dioxide.

Manufacturers make sunscreens with zinc oxide or titanium dioxide just for children.

For whitening purposes, titanium dioxide may be used to create a softer tone.

It purges the body of carbon dioxide, oxygenates the blood, and promotes relaxation.

While all melt and pour soaps start out transparent, sometimes titanium dioxide has been added to the soap base to make it opaque.

It is comprised of silicon dioxide and is used as an additive which absorbs excess liquid in some foods.

They estimate calories burned during exercise based on oxygen, carbon dioxide, and heat output generated during exercise.

Automobiles, on the other hand, are the second largest source of total carbon dioxide emissions.

Laser treatment for acne scars typically uses a combination of a carbon dioxide and an erbium laser.

As the ingredients react together, they release carbon dioxide, thus accounting for the innumerable bubbles released when the bomb hits the water.

Consisting of titanium dioxide and zinc oxide, it's an easily applied powder that goes well over most makeup.

In addition to the above ingredients, it also contains Titanium Dioxide, which serves to enhance the product's overall protection.

Iridium sesquioxide, Ir 2 0 3, is obtained when potassium iridium chloride is heated with sodium or potassium carbonates, in a stream of carbon dioxide.

Cobalt monoxide, CoO, is prepared by heating the hydroxide or carbonate in a current of air, or by heating the oxide C0304 in a current of carbon dioxide.

The ammonium cobalto-cobaltisulphite is prepared by saturating an air-oxidized ammoniacal solution of cobaltous chloride with sulphur dioxide.

Hot concentrated sulphuric acid also decomposes allantoin, with production of ammonia, and carbon monoxide and dioxide.

With bromine in acetic acid solution at ordinary temperature, nicotine yields a perbromide, C10H10Br2N20 HBr 3, which with sulphur dioxide, followed by potash, gives dibromcotinine, C10H10Br2N20, from which cotinine, C10H12N20, is obtained by distillation over zinc dust.

This comes in almost all such cases from the decomposition of sugar, which is split up by the protoplasm into alcohol and carbon dioxide.

Doubtless, the excess of any soluble mineral salt or salts interferes with the osmotic absorption of the roots; and although calcium carbonate is insoluble in pure water, it is slightly soluble in water containing carbon dioxide.

The chamber has a safety value at the top of its vault, which is so balanced that the least surplus pressure from within sends it up. The first puff of sulphur vapour which enters the chamber takes fire and converts the air of the chamber into a mixture of nitrogen and sulphur dioxide.

The free acid has not been isolated, since on evaporation the solution gradually loses sulphur dioxide.

This solution is yellow in colour, and is very unstable decomposing at ordinary temperature into sulphur and sulphur dioxide.

A solution of the free acid may be obtained by decomposing the barium salt with dilute sulphuric acid and concentrating the solution in vacuo until it attains a density of about 1.35 (approximately), further concentration leading to its decomposition into sulphur dioxide and sulphuric acid.

In its vivid blue colour it contrasts strikingly with the emerald-green malachite, also a basic copper carbonate, but containing rather more water and less carbon dioxide.

Azurite occurs with malachite in the upper portions of deposits of copper ore, and owes its origin to the alteration of the sulphide or of native copper by water containing carbon dioxide and oxygen.

Thus if concentrated instead of dilute sulphuric acid acts upon zinc, the action takes place to a great extent not according to the equation given above, but according to the equation Zn +2H 2 SO 4 = ZnS04+S02+2 H20, sulphur dioxide and water being produced instead of hydrogen.

In the above instance the sulphur is supposed to be in the solid rhombic modification, the oxygen and sulphur dioxide being in the gaseous state, and the initial and final systems being at the ordinary temperature.

He thus writes S+02=S02+7110o cal., which expresses the fact that the intrinsic energy of the quantities of sulphur and oxygen considered exceeds that of the sulphur dioxide derived from them by 71100 cal.

The hydrocarbon methane, CH 4, when completely burned to carbon dioxide and water, generates 213800 cal.

Now we know the heats of formation of carbon dioxide (from diamond) and of liquid water to be 94300 cal.

These esters are readily hydrolysed and yield the monoand di-alkylimalonic acids which, on heating, are readily decomposed, with evolution of carbon dioxide and the formation of monoand di-alkyl acetic acids.

Then he treated oil of vitriol in the same way, but got nothing until by accident he dropped some mercury into the liquid, when "vitriolic acid air" (sulphur dioxide) was evolved.

A higher temperature decomposes this body into carbon dioxide and itaconic acid, C 5 H 6 0 4, which, again, by the expulsion of a molecule of water, yields citraconic anhydride, C 5 H 4 0 3.

Natural gas is found to consist mainly of the lower paraffins, with varying quantities of carbon dioxide, carbon monoxide, hydrogen, nitrogen and oxygen, in some cases also sulphuretted hydrogen and possibly ammonia.

Now, however, the mottled soaps, blue and grey, are produced by working colouring matter, ultramarine for blue, and manganese dioxide for grey, into the soap in the frame, and mottling is very far from being a certificate of excellence of quality.

It burns with a pale blue flame to form carbon dioxide and sulphur dioxide.

When passed with carbon dioxide through a red-hot tube it yields carbon oxysulphide, COS (C. Winkler), and when passed over sodamide it yields ammonium thiocyanate.

Carbon bisulphide slowly oxidizes on exposure to air, but by the action of potassium permanganate or chromic acid it is readily oxidized to carbon dioxide and sulphuric acid.

The dioxide, Ru02, is formed by heating sulphate, or by heating the metal in a current of oxygen.

He also showed that on heating mercury calx alone an " air " was liberated which differed from other " airs," and was slightly heavier than ordinary air; moreover, the weight of the " air " set free from a given weight of the calx was equal to the weight taken up in forming the calx from mercury, and if the calx be heated with charcoal, the metal was recovered and a gas named " fixed air," the modern carbon dioxide, was formed.

A masterly device, initiated by him, was to collect gases over mercury instead of water; this enabled him to obtain gases previously only known in solution, such as ammonia, hydrochloric acid, silicon fluoride and sulphur dioxide.

The term allotropy has also been applied to inorganic compounds, identical in composition, but assuming different crystallographic forms. Mercuric oxide, sulphide and iodide; arsenic trioxide; titanium dioxide and silicon dioxide may be cited as examples.

Strong oxidation breaks the benzene complex into such compounds, as carbon dioxide, oxalic acid, formic acid, &c.; such decompositions are of little interest.

By reducing terephthalic acid with sodium amalgam, care being taken to neutralize the caustic soda simultaneously formed by passing in carbon dioxide, A" dihydroterephthalic acid is obtained; this results from the splitting of a Para-linkage.

He applied himself more particularly to the oxygen compounds, and determined with a fair degree of accuracy the ratio of carbon to oxygen in carbon dioxide, but his values for the ratio of hydrogen to oxygen in water, and of phosphorus to oxygen in phosphoric acid, are only approximate; he introduced no new methods either for the estimation or separation of the metals.

Sulphur dioxide, recognized by its smell and acid reaction, results from the ignition of certain sulphites, sulphates, or a mixture of a sulphate with a sulphide.

Carbon dioxide, recognized by turning lime-water milky, indicates decomposable carbonates or oxalates.

Carbon is detected by the formation of carbon dioxide, which turns lime-water milky, and hydrogen by the formation of water, which condenses on the tube, when the substance is heated with copper oxide.

Lead chromate is sometimes used, and many other substances, such as platinum, manganese dioxide, &c., have been suggested.

The increase in weight of the calcium chloride tube gives the weight of water formed, and of the potash bulbs the carbon dioxide.

In 1855 C. Brunner described a method for oxidizing the carbon to carbon dioxide, which could be estimated by the usual methods, by heating the substance with potassium bichromate and sulphuric acid.

The oxidation, which is effected by chromic acid and sulphuric acid, is conducted in a flask provided with a funnel and escape tube, and the carbon dioxide formed is swept by a current of dry air, previously freed from carbon dioxide, through a drying tube to a set of potash bulbs and a tube containing soda-lime; if halogens are present, a small wash bottle containing potassium iodide, and a U tube containing glass wool moistened with silver nitrate on one side and strong sulphuric acid on the other, must be inserted between the flask and the drying tube.

The increase in weight of the potash bulbs and soda-lime tube gives the weight of carbon dioxide evolved.

Bevan collected the carbon dioxide obtained in this way over mercury.

The magnesite (a) serves for the generation of carbon dioxide which clears the tube of air before the compound (mixed with fine copper oxide (b)) is burned, and afterwards sweeps the liberated nitrogen into the receiving vessel (e), which contains a strong potash solution; c is coarse copper oxide; and d a reduced copper gauze spiral, heated in order to decompose any nitrogen oxides.

Ulrich Kreusler generates the carbon dioxide in a separate apparatus, and in this case the tube is drawn out to a capillary at the end (a).

This artifice is specially valuable when the substance decomposes or volatilizes in a warm current of carbon dioxide.

The value of d can be evaluated by considering the combustion of amorphous carbon to carbon monoxide and carbon dioxide.

Manasse (German patent 73,279) prepared an intimate mixture of phenol and potassium carbonate, which is then heated in a closed vessel with carbon dioxide, best at 130 -160 C. The Chemische Fabrik vorm.

It sublimes, but on rapid heating decomposes into carbon dioxide and phenol.

Potassium bichromate and sulphuric acid oxidize it to carbon dioxide and water; and potassium chlorate and hydrochloric acid to chloranil.

When heated in air for many hours it decomposes, yielding carbon dioxide, phenol and xanthone.

In de Lambilly's process air and steam is led over white-hot coke, and carbon dioxide or monoxide removed from the escaping gases according as ammonium formate or carbonate is wanted.

Acetonyl-acetophenone, C6H5.CO.CH2.CH2.CO.CH3, is produced by condensing phenacyl bromide with sodium acetoacetate with subsequent elimination of carbon dioxide, and on dehydration gives aa-phenyl-methyl-furfurane.

Boiling with dilute mineral acids, or baryta water, decomposes albumins into carbon dioxide, ammonia and fatty aminoand other acids.

Haemoglobin is composed of a basic albumin and an acid substance haematin; it combines readily with oxygen, carbon dioxide and carbon monoxide to form loose compounds.

If the current be so strong that new hydrogen and hydroxyl ions cannot be formed in time, other substances are liberated; in a solution of sulphuric acid a strong current will evolve sulphur dioxide, the more readily as the concentration of the solution is increased.

It appears to be synthesized in the plant tissues from carbon dioxide and water, formaldehyde being an intermediate product; or it may be a hydrolytic product of a glucoside or of a polysaccharose, such as cane sugar, starch, cellulose, &c. In the plant it is freely converted into more complex sugars, poly-saccharoses and also proteids.

It is decomposed, on dry distillation, into carbon dioxide and pyromellitic acid, C i oH 6 0 8 i when distilled with lime it gives carbon dioxide and benzene.

Boiling concentrated sulphuric acid converts lead into sulphate, with evolution of sulphur dioxide.

It absorbs carbon dioxide from the air when moist.

A hydrated oxide, 2PbO H 2 O, is obtained when a solution of the monoxide in potash is treated with carbon dioxide.

Lead dioxide, Pb0 2, also known as "puce oxide," occurs in nature as the mineral plattnerite, and may be most conveniently prepared by heating mixed solutions of lead acetate and bleaching powder until the original precipitate blackens.

The Kassner process for the manufacture of oxygen depends upon the formation of calcium plumbate, Ca2Pb04, by heating a mixture of lime and litharge in a current of air, decomposing this substance into calcium carbonate and lead dioxide by heating in a current of carbon dioxide, and then decomposing these compounds with the evolution of carbon dioxide and oxygen by raising the temperature.

With water it forms a hydrate, and ultimately decomposes into lead dioxide and hydrochloric acid.

It is decomposed by acids into a mixture of lead monoxide and dioxide, and may thus be regarded as lead metaplumbate, PbPbO 3.

Acids decompose it into lead dioxide and monoxide, and the latter may or may not dissolve to form a salt; red lead may, therefore, be regarded as lead orthoplumbate, Pb2Pb04.

By the action of the acetic acid and atmospheric oxygen, the lead is converted superficially into a basic acetate, which is at once decomposed by the carbon dioxide, with formation of white lead and acetic acid, which latter then acts de novo.

These are knocked off, ground up with water, freed from metal-particles by elutriation, and the paste of white lead is allowed to set and dry in small conical forms. The German method differs from the Dutch inasmuch as the lead is suspended in a large chamber heated by ordinary means, and there exposed to the simultaneous action of vapour of aqueous acetic acid and of carbon dioxide.

Another process depends upon the formation of lead chloride by grinding together litharge with salt and water, and then treating the alkaline fluid with carbon dioxide until it is neutral.

When carbon dioxide is passed into this solution the whole of the added oxide, and even part of the oxide of the normal salt, is precipitated as a basic carbonate chemically similar, but not quite equivalent as a pigment, to white lead.

By this means, sodium aluminate is formed; it is then extracted with water and precipitated either by sodium bicarbonate or by passing a current of carbon dioxide through the solution.

When heated in a current of carbon dioxide it forms the oxychloride CbOC1 3, and carbon monoxide.

It burns when heated in air, forming the pentoxide and sulphur dioxide.

Uranous Compounds.-Uranium dioxide, UO 2 (Berzelius's metal), is a brown to copper-coloured powder, obtained by heating U308 or uranyl oxalate in hydrogen.

By electrolysis it yields uranium dioxide as a pyrophoric powder, and peruranic hydroxide, U04.2H20, when treated with hydrogen peroxide.

Uranyl chloride, UO 2 C1 2, is a yellow crystalline mass formed when chlorine is passed over uranium dioxide at a red heat.

A hydrated tin trioxide, Sn03, was obtained by Spring by adding barium dioxide to a solution of stannous chloride and hydrochloric acid; the solution is dialysed, and the colloidal solution is evaporated to form a white mass of 2Sn03 H20.

Tin is generally quantitatively estimated as the dioxide.

On oxidation with potassium permanganate it gives homovanillin, vanillin, &c.; with chromic acid in acetic acid solution it is converted into carbon dioxide and acetic acid, whilst nitric acid oxidizes it to oxalic acid.

The gaseous mixture obtained by burning guncotton in a vacuum vessel contains steam, carbon monoxide, carbon dioxide, nitrogen, nitric oxide, and methane.

When slowly heated in a vacuum vessel until ignition takes place, some nitrogen dioxide, N02, is also produced.

By eliminating carbon dioxide, phenylmethyltriazole results.

For example, carbon dioxide occurs in some mines, and hydrogen sulphide, which is a poisonous gas, in others.

The gases produced by such fire-damp or dust explosions contain carbon dioxide and carbon monoxide in large proportion, and the majority of the deaths from such explosions are due to this " after-damp " rather than to the explosion itself.

The efficiency of such ventilating furnaces is low, and they cannot safely be used in mines producing fire-damp. They are sometimes the cause of underground fires, and they are always a source of danger when by any chance the ventilating current becomes reversed, in which case the products of combustion, containing large quantities of carbon dioxide, will be drawn into the mine to the serious danger of the men.

Oxidation may be effected by the addition to the glass mixture of a substance which gives up oxygen at a high temperature, such as manganese dioxide or arsenic trioxide.

Manganese dioxide not only acts as a source of oxygen, but develops a pink tint in the glass, which is complementary to and neutralizes the green colour due to ferrous oxide.

A certain proportion of soda ash (carbonate of soda) is also used in some works in sheet-glass mixtures, while " decolorizers " (substances intended to remove or reduce the colour of the glass) are also sometimes added, those most generally used being manganese dioxide and arsenic. Another essential ingredient of all glass mixtures containing sulphate of soda is some form of carbon, which is added either as coke, charcoal or anthracite coal; the carbon so introduced aids the reducing substances contained in the atmosphere of the furnace in bringing about the reduction of the sulphate of soda to a condition in which it combines more readily with the silicic acid of the sand.

Silicon tetraiodide, Si14, is formed by passing iodine vapour mixed with carbon dioxide over strongly-heated silicon (C. Friedel, Comptes rendus, 1868, 67, p. 98); the iodo-compound condenses in the colder portion of the apparatus and is purified by shaking with carbon bisulphide and with mercury.

The acid carbonates of the alkali metals can be prepared by saturating an aqueous solution of the alkaline hydroxide with carbon dioxide, M OH+ C02= Mhco 3, and from these acid salts the normal salts may be obtained by gentle heating, carbon dioxide and water being produced at the same time, 2Mhco 3 = M2C03+H02+C02.

All carbonates, except those of the alkali metals and of thallium, are insoluble in water; and the majority decompose when heated strongly, carbon dioxide being liberated and a residue of an oxide of the metal left.

The carbonates are decomposed by mineral acids, with formation of the corresponding salt of the acid, and liberation of carbon dioxide.

Many carbonates which are insoluble in water dissolve in water containing carbon dioxide.

Dumas obtained barium methyl carbonate by the action of carbon dioxide on baryta dissolved in methyl alcohol (Ann., 1840, 35, p. 283).

It is easily broken down by many substances (aluminium chloride, zinc chloride, &c.) into ethyl chloride and carbon dioxide.

Sodium percarbonates of the formulae Na 2 CO 4, Na2C206, Na 2 C05, NaHCO 4 (two isomers) are obtained by the action of gaseous or solid carbon dioxide on the peroxides Na 2 0 2, Na 2 0 3, NaHO 2 (two isomers)in the presence of water at a low temperature (R.Wolffenstein and E.Peltner, Ber., 1908, 41, pp. 275, 280).

Hot (concentrated) sulphuric acid does not attack gold, platinum and platinum-metals generally; all other metals (including silver) are converted into sulphates, with evolution of sulphur dioxide.

Manganese dioxide and sulphuric acid oxidize it to benzoic and o-phthalic acid; potassium chlorate and sulphuric acid breaks the ring; and ozone oxidizes it to the highly explosive white solid named ozo-benzene, C 6 H 6 O 6.

Their "firedamp" (formerly fulminating damp) is marsh gas, which, when mixed with air and exploded, produced "choke damp," "after damp," or "suffocating damp" (carbon dioxide).

This disintegration is brought about chiefly by changes in temperature, and by the action of the rain, the oxygen, and the carbon dioxide of the air.

In the case of limestones the carbon dioxide of the air in association with rain and dew eats into them and leads to their disintegration.

If the latter is too compact or has its interstices filled with carbon dioxide gas or with water - as is the case when the ground is water-logged - the roots rapidly die of suffocation just as would an animal under the same conditions.

Chemically pure sand is silicon dioxide (SiO 2) or quartz, a clear transparent glass-like mineral, but as ordinarily met with, it is more or less impure and generally coloured reddish or yellowish by oxide of iron.

Pure carbonate of lime when heated loses 44% of its weight, the decrease being due to the loss of carbon dioxide gas.

This substance absorbs and combines with water very greedily, at the same time becoming very hot, and falling into a fine dry powder,' calcium hydroxide or slaked lime, which when left in the open slowly combines with the carbon dioxide of the air and becomes calcium carbonate, from which we began.

The oxygen, however, decreases with the depth, while the carbon dioxide increases.

Oxide of zinc, like most heavy metallic oxides, is easily reduced to the metallic state by heating it to redness with charcoal; pure red zinc ore may be treated directly; and the same might be done with pure calamine of any kind, because the carbon dioxide of the zinc carbonate goes off below redness and the silica of zinc silicate only retards, but does not prevent, the reducing action of the charcoal.

The anhydrous salt, when exposed to a red heat, breaks up into oxide, sulphur dioxide and oxygen.

Rejecting the old notion that plants derive their nourishment from humus, he taught that they get carbon and nitrogen from the carbon dioxide and ammonia present in the atmosphere, these compounds being returned by them to the atmosphere by the processes of putrefaction and fermentation - which latter he regarded as essentially chemical in nature - while their potash, soda, lime, sulphur, phosphorus, &c., come from the soil.

Of the carbon dioxide and ammonia no exhaustion can take place, but of the mineral constitutents the supply is limited because the soil cannot afford an indefinite amount of them; hence the chief care of the farmer, and the function of manures, is to restore to the soil those minerals which each crop is found, by the analysis of its ashes, to take up in its growth.

The commonest titanium mineral is rutile or titanium dioxide, T102; anatase and brookite are crystalline allotropes.

Titanium dioxide, T102, occurs in nature as the three distinct mineral species rutile, brookite and anatase.

Titanium monoxide, TiO, is obtained as black prismatic crystals by heating the dioxide in the electric furnace, or with magnesium powder.

Titanium sesquioxide, Ti 2 O 3, is formed by heating the dioxide in hydrogen.

When shaken with potash and air it undergoes autoxidation, hydrogen peroxide being formed first, which converts the trioxide into the dioxide and possibly pertitanic acid.

By dissolving the dioxide in hydrofluoric acid a syrupy solution is obtained which probably contains titanofluoric acid, H 2 TiF 6.

By passing chloroform vapour over the heated dioxide the tetradiand tri-chlorides are formed, together with the free metal and a gaseous hydride, TiH 4 (Renz, Ber., 1906, 39, p. 2 49).

It forms many crystalline salts and absorbs carbon dioxide.

Manganese dioxide and dilute sulphuric acid oxidize it to quinone.

Dittmar showed that this may be avoided by leading a fine, steady stream of dry gas - air, carbon dioxide, hydrogen, &c., according to the substance operated upon - through the liquid by means of a fine capillary tube, the lower end of which reaches to nearly the bottom of the flask.

With substances prone to discolorization, as, for example, certain amino compounds, the operation may be conducted in an atmosphere of carbon dioxide, or the water may be saturated with sulphuretted hydrogen.

Sidney Young has suggested conducting the operation in a current of carbon dioxide which sweeps out the vapours as they are evolved, and also heating in a vapour bath, e.g.

Operating in a current of carbon dioxide facilitates the process by preventing overheating.

It is used in the extraction of sugar from molasses, since it combines with the sugar to form a soluble saccharate, which is removed and then decomposed by carbon dioxide.

A hydrated dioxide, approximating in composition to SrO 2.8H 2 O, is formed as a crystalline precipitate when hydrogen peroxide is added to an aqueous solution of strontium hydroxide.

It loses carbon dioxide when heated to high temperature.

Again, anode reactions, such as are observed in the electrolysis of the fatty acids, may be utilized, as, for example, when the radical CH3C02 - deposited at the anode in the electrolysis of acetic acid - is dissociated, two of the groups react to give one molecule of ethane, C 2 H 6, and two of carbon dioxide.

The simplest syntheses are undoubtedly those in which a carboxyl group is obtained directly from the oxides of carbon, carbon dioxide and carbon monoxide.

Phosphorus pentachloride decomposes it into carbon monoxide and dioxide, the reaction being the one generally applied for the purpose of preparing phosphorus oxychloride.

When heated with glycerin to ioo C. it yields formic acid and carbon dioxide; above this temperature, allyl alcohol is formed.

Potassium permanganate in acid solution oxidizes it to carbon dioxide and water; the manganese sulphate formed has a catalytic accelerating effect on the decomposition.

It is also obtained by the action of hydrogen peroxide on hydrocyanic acid, or of manganese dioxide and sulphuric acid on potassium cyanide.

It readily inflames, burning with a blue smokeless flame, and producing water and carbon dioxide, with the evolution of great.

Graham showed that gold is capable of occluding by volume 0.48% of hydrogen, 0.20% of nitrogen, 0.29% of carbon monoxide, and 0.16% of carbon dioxide.

Precipitation with sulphur dioxide and sulphuretted hydrogen proceeds much more rapidly, and has been adopted at many works.

Sulphur dioxide, generated by burning sulphur, is forced into the solution under pressure, where it interacts with any free chlorine present to form hydrochloric and sulphuric acids.

Elsner recognized, in 1846, the part played by the atmosphere, and in 1879 Dixon showed that bleaching powder, manganese dioxide, and other oxidizing agents, facilitated the solution.

In the last case it becomes coated with a greyish-black layer of an oxide (dioxide (?)), at a red heat the layer consists of the trioxide (B1203), and is yellow or green in the case of pure bismuth, and violet or blue if impure; at a bright red heat it burns with a bluish flame to the trioxide.

Bismuth dioxide, BiO or Bi 2 O 2, is said to be formed by the limited oxidation of the metal, and as a brown precipitate by adding mixed solutions of bismuth and stannous chlorides to a solution of caustic potash.

The crude element is treated with aqua regia and then evaporated with an excess of hydrochloric acid, the solution diluted and the tellurium precipitated by a current of sulphur dioxide.

An amor phous form is obtained when tellurium is precipitated from its solutions by sulphur dioxide, this variety having a specific gravity 6.015.

Two oxides of the element are definitely known, viz., the dioxide, Te02, and the trioxide, Te03, whilst a monoxide, TeO, has also been described.

The dioxide is formed by burning tellurium in air or xxvi.

Caesium hydroxide, Cs(OH) 2, obtained by the decomposition of the sulphate with baryta water,is a greyish-white deliquescent solid,which melts at a red heat and absorbs carbon dioxide rapidly.

For its complete combustion a volume of acetylene needs approximately twelve volumes of air, forming as products of combustion carbon dioxide and water vapour.

When, however, the air is present in much smaller ratio the combustion is incomplete, and carbon, carbon monoxide, carbon dioxide, hydrogen and water vapour are produced.

Although at the present time a marvellous improvement has taken place all round in the quality of the carbide produced, the acetylene nearly always contains minute traces of hydrogen, ammonia, sulphuretted hydrogen, phosphuretted hydrogen, silicon hydride, nitrogen and oxygen, and sometimes minute traces of carbon monoxide and dioxide.

The tetroxide, 0s04, can be easily reduced to the metal by dissolving it in hydrochloric acid and adding zinc, mercury, or an alkaline formate to the liquid, or by passing its vapour, mixed with carbon dioxide and monoxide, through a red-hot porcelain tube.

The protoxide, OsO, is obtained as a dark grey insoluble powder when osmium sulphite is heated with sodium carbonate in a current of carbon dioxide.

The dioxide, 0s0 2, is formed when potassium osmichloride is heated with sodium carbonate in a current of carbon dioxide, or by electrolysis of a solution of the tetroxide in the presence of alkali.

Carbon dioxide is invariably present, as was inferred by Dr David Macbride (1726-1778) of Dublin in 1764, but in a proportion which is not absolutely constant; it tends to increase at night, and during dry winds and fogs, and it is greater in towns than in the country and on land than on the sea.

Hydrogen dioxide occurs in a manner closely resembling ozone.

On heating with an oxide or carbonate they yield a trimetallic orthophosphate, carbon dioxide being evolved in the latter case.

This formula was very nearly confirmed for hydrogen, carbon dioxide and nitrous oxide.

The dissipation of the dissolved carbon dioxide results in the formation of "fur" in kettles or boilers, and if the solution is falling, as from the roof of a cave, in the formation of stalactites and stalagmites.

It is obtained as rhombic plates by mixing dilute solutions of calcium chloride and sodium phosphate, and passing carbon dioxide into the liquid.

Calcium sulphite, CaSO 3, a white substance, soluble in water, is prepared by passing sulphur dioxide into milk of lime.

This solution with excess of sulphur dioxide yields the "bisulphite of lime" of commerce, which is used in the "chemical" manufacture of woodpulp for paper making.

The aqueous solution of this salt liberates carbon dioxide on exposure to air or on heating, and becomes alkaline in reaction.

The aqueous solutions of all the carbonates when boiled undergo decomposition with liberation of ammonia and of carbon dioxide.

Exposed to moist air it rapidly oxidizes to the hydroxide; and it burns on heating in air with a yellow flame, yielding the monoxide and dioxide.

Heated in a current of carbon dioxide sodamide yields caustic soda and cyanamide, and with nitrous oxide it gives sodium azoimide; it deflagrates with lead or silver nitrate and explodes with potassium chlorate.

Dry carbon dioxide is decomposed by it, free carbon being produced; moist carbon dioxide, on the other hand, gives sodium formate.

It absorbs moisture and carbon dioxide from the atmosphere.

In practice the metal is placed on aluminium trays traversing an iron tube heated to 300 0, through which a current of air, freed from moisture and carbon dioxide, is passed; the process is made continuous, and the product contains about 93% Na202.

Acids yield a sodium salt and free oxygen or hydrogen peroxide; with carbon dioxide it gives sodium carbonate and free oxygen; carbon monoxide gives the carbonate; whilst nitrous and nitric oxides give the nitrate.

Sodium dioxide is chiefly employed as an oxidizing agent, being used in mineral analysis and in various organic preparations; it readily burns paper, wood, &c., but does not evolve oxygen unless heated to a high temperature.

Water decomposes it, giving oxygen and the dioxide.

Sodium sulphite, Na2S03, which is employed as an antichlor, is prepared (with 7H20) by saturating a solution of sodium carbonate with sulphur dioxide, adding another equivalent of carbonate and crystallizing.

The acid sulphite, NaHSO 3, obtained by saturating a cold solution of the carbonate with sulphur dioxide and precipitating by alcohol, is employed for sterilizing beer casks.

We may here notice the "percarbonates" obtained by Wolffenstein and Peltner (Ber., 1908, 41, pp. 2 75, 280) on acting with gaseous or solid carbon dioxide on Na202, Na203 and NaHO 2 at low temperatures; the same authors obtained a perborate by adding sodium metaborate solution to a 50% solution of sodium peroxide previously saturated with carbon dioxide.

In combination with oxygen (as carbon dioxide) it is also found to a small extent in the atmosphere.

It burns when heated in an atmosphere of oxygen, forming carbon dioxide, and when heated in sulphur vapour it forms carbon bisulphide.

Three oxides of carbon are known, namely, carbon suboxide, C,02, carbon monoxide, CO, and carbon dioxide, C02.

It may be prepared by passing carbon dioxide over red-hot carbon, or red-hot iron; by heating carbonates (magnesite, chalk, &c.) with zinc dust or iron; or by heating many metallic oxides with carbon.

It may also be prepared by heating formic and oxalic acids (or their salts) with concentrated sulphuric acid (in the case of oxalic acid, an equal volume of carbon dioxide is produced); and by heating potassium ferrocyanide with a large excess of concentrated sulphuric acid, K 4 Fe(CN) 6 -i-6H2S04+6H20=2K2S04+FeS04+3(NH4)2S04+6C0.

It burns with a characteristic pale blue flame to form carbon dioxide.

The volume composition of carbon monoxide is established by exploding a mixture of the gas with oxygen, two volumes of the gas combining with one volume of oxygen to form two volumes of carbon dioxide.

Carbon dioxide, C02, is a gas first distinguished from air by van Helmont (1577-1644), who observed that it was formed in fermentation processes and during combustion, and gave to it the name gas sylvestre.

The volume composition of carbon dioxide is determined by burning carbon in oxygen, when it is found that the volume of carbon dioxide formed is the same as that of the oxygen required for its production, hence carbon dioxide contains its own volume of oxygen.

Carbon dioxide finds industrial application in the preparation of soda by the Solvay process, in the sugar industry, in the manufacture of mineral waters, and in the artificial production of ice.

Water decomposes it violently, with formation of carbon dioxide and hydrochloric acid.

It Is Soluble In Water; The Aqueous Solution Gradually Decomposes On Standing, Forming Carbon Dioxide And Sulphuretted Hydrogen.

The solution is strongly caustic. It turns yellow on exposure to air, absorbing oxygen and carbon dioxide and forming thiosulphate and potassium carbonate and liberating sulphuretted hydrogen, which decomposes into water and sulphur, the latter combining with the monosulphide to form higher salts.

Potassium sulphite, K 2 S0 3, is prepared by saturating a potash solution with sulphur dioxide, adding a second equivalent of potash, and crystallizing in a vacuum, when the salt separates as small deliquescent, hexagonal crystals.

The salt K2S03 H20 may be obtained by crystallizing the metabisulphite, K 2 S 2 0 5 (from sulphur dioxide and a hot saturated solution of the carbonate, or from sulphur dioxide and a mixture of milk of lime and potassium sulphate) with an equivalent amount of potash.

The analysis of manganese dioxide in 1774 led him to the discovery of chlorine and baryta; to the description of various salts of manganese itself, including the manganates and permanganates, and to the explanation of its action in colouring and decolourizing glass.

Nencki has shown that alloxan combines with thiourea in alcoholic solution, in the presence of sulphur dioxide to form pseudothiouric acid, C 5 H 6 N 4 S0 3.

The liquid is run into the iodine still and gently warmed, manganese dioxide in small quantities being added from time to time, when the iodine distils over and is collected.

Iodine may also be prepared by the decomposition of an iodide with chlorine, or by heating a mixture of an iodide and manganese dioxide with concentrated sulphuric acid.

The acid cannot be prepared by the action of concentrated sulphuric acid on an iodide on account of secondary reactions taking place, which result in the formation of free iodine and sulphur dioxide.

Nitrous acid and chlorine readily decompose them with liberation of iodine; the same effect being produced when they are heated with concentrated sulphuric acid and manganese dioxide.

The free acid, when heated with concentrated sulphuric acid, is decomposed into water and pure carbon monoxide; when heated with nitric acid, it is oxidized first to oxalic acid and finally to carbon dioxide.

The silver and mercury salts, when heated, yield the metal, with liberation of carbon dioxide and formation of free formic acid; and the ammonium salt, when distilled, gives some formamide, Hconh 2.

Various other oxides of chromium, intermediate in composition between the sesquioxide and trioxide, have been described, namely chromium dioxide, Cr203 Cr03, and the oxide Cr03.2Cr203.

Gases, like atmospheric air, hydrogen or carbon dioxide do not become luminous if they are placed in tubes, even when heated up far beyond white heat as in the electric furnace.

Paschen proved that the emission spectra of water vapour as observed in an oxyhydrogen flame, and of carbon dioxide as observed in a hydrocarbon flame may be obtained by heating aqueous vapour and carbon dioxide respectively to a few hundred degrees above the freezing point.

It is a non-volatile and almost infusible white powder, which slowly absorbs moisture and carbon dioxide from air, and is readily soluble in dilute acids.

It possesses an alkaline reaction and absorbs carbon dioxide.

The carbonate is not easily soluble in dilute acids, but is readily soluble in water containing carbon dioxide.

When heated in a current of carbon monoxide or dioxide, it is converted into oxide, some carbon and cyanogen being formed at the same time.

The salts of the normal or orthoboric acid in all probability do not exist; metaboric acid, however, forms several well-defined salts which are readily converted, even by carbon dioxide, into salts of pyroboric acid.

In order to prepare pure alumina, bauxite and sodium carbonate were heated in a furnace until the reaction was complete; the product was then extracted with water to dissolve the sodium aluminate, the solution treated with carbon dioxide, and the precipitate removed and dried.

The operation is essentially a dissociation of alumina into aluminium, which collects at the cathode, and into oxygen, which combines with the anodes to form carbon monoxide, the latter escaping and being burnt to carbon dioxide outside.

Nutrition (assimilation) by the leaves includes the inhalation of air, and the interaction under the influence of light and in the presence of chlorophyll of the carbon dioxide of the air with the water received from the root, to form carbonaceous food.

This process, which is as yet imperfectly understood, is attended by the consumption of oxygen, the liberation of energy in the form of heat, and the exhalation of carbon dioxide and water vapour.

Tudsbury that if an influence machine is enclosed in a metallic chamber containing compressed air, or better, carbon dioxide, the insulating properties of compressed gases enable a greatly improved effect to be obtained owing to the diminution of the leakage across the plates and from the supports.

But there is no good evidence for an excess of carbon dioxide in the atmosphere - an assumption founded on the luxuriance of the vegetation, coupled with the fact that volcanicity was active and wide-ranging.

Carbon dioxide may have been present in the air in greater abundance in earlier periods than it is at present, but there is no reason to suppose that the percentage was appreciably higher in the Carboniferous period than it is now.

Dilute nitric acid oxidizes it to acetic and oxalic acids, while potassium permanganate oxidizes it to acetone, carbon dioxide and oxalic acid.

The want of chlorophyll restricts their mode of life - which is rarely aquatic - since they are therefore unable to decompose the carbon dioxide of the atmosphere, and renders them dependent on other plants or (rarely) animals for their carbonaceous food-materials.

It may be recognized by the violet coloration it gives when added to a very dilute solution of potassium bichromate in the presence of hydrochloric acid; by the orange-red colour it gives with a solution of titanium dioxide in concentrated sulphuric acid; and by the precipitate of Prussian blue formed when it is added to a solution containing ferric chloride and potassium ferricyanide.

Experiments on the combustion of diamond were made by Smithson Tennant (1797) and Sir Humphry Davy (1816), with the object of proving that it is pure carbon; they showed that burnt in oxygen it yields exactly the same amount of carbon dioxide as that produced by burning the same weight of carbon.

Liquid inclusions, some of which are certainly carbon dioxide, have also been observed.

The flat surface is spread to allow the maximum amount of sunlight to fall upon it, as it is by the absorption of energy from the sun's rays by means of the chlorophyll contained in the cells of the leaf that the building up of plant food is rendered possible; this process is known as photo-synthesis; the first stage is the combination of carbon dioxide, absorbed from the air taken in through the stomata into the living cells of the leaf, with water which is brought into the leaf by the wood-vessels.

Several basic carbonates are known, being formed by the addition of beryllium salts to solutions of the alkaline carbonates; the normal carbonate is prepared by passing a current of carbon dioxide through water containing the basic carbonate in suspension, the solution being filtered and concentrated over sulphuric acid in an atmosphere of carbon dioxide.

The crystals so obtained are very unstable and decompose rapidly with evolution of carbon dioxide.

Potassium bichromate and sulphuric acid oxidize it to carbon dioxide and acetic acid, while alkaline potassium permanganate oxidizes it to carbon dioxide.

By continued boiling of its aqueous solution it is decomposed into carbon dioxide and glyoxylic acid, C2H404.

Minute vesicular cavities are not infrequently present, sometimes as negative cubes, and these may contain saline solutions or carbon dioxide or gaseous hydrocarbons.

It is produced by the exposure of thallous hydrate to carbon dioxide, and therefore is obtained when the moist metal is exposed to the air.

Thallous sulphate, T1 2 SO 4, forms rhombic prisms, soluble in water, which melt at a red heat with decomposition, sulphur dioxide being evolved.

Alkaline hypobromites or hypochlorites or nitrous acid decompose urea into carbon dioxide and nitrogen.

It is also decomposed by warm aqueous solutions of caustic alkalis, with evolution of ammonia and carbon dioxide.

Acid potassium permanganate oxidizes it to carbon dioxide and nitrogen.

When heated with water it is decomposed into carbon dioxide, ammonia, methylamine and acetic acid.

Allophanic acid, NH 2 C0 NH CO 2 H, is not known in the free state, as when liberated from its salts, it is decomposed into urea and carbon dioxide.

Baryta water hydrolyses it to carbon dioxide, ammonia and urea.

It is hydrolysed by alkalis, giving carbon dioxide, ammonia and sulphuretted hydrogen.

It is also disengaged by growing vegetation, plants possessing the power of absorbing carbon dioxide, assimilating the carbon and rejecting the oxygen.

Oxygen may be prepared by heating mercuric oxide; by strongly heating manganese dioxide and many other peroxides; by heating the oxides of precious metals; and by heating many oxy-acids and oxy-salts to high temperatures, for example, nitric acid, sulphuric acid, nitre, lead nitrate, zinc sulphate, potassium chlorate, &c. Potassium chlorate is generally used and the reaction is accelerated and carried out at a lower temperature by previously mixing the salt with about one-third of its weight of manganese dioxide, which acts as a catalytic agent.

Its dioxide (pyrolusite) has been known from very early times, and was at first mistaken for a magnetic oxide of iron.

It is almost impossible to prepare a pure hydrated manganese dioxide owing to the readiness with which it loses oxygen, leaving residues of the type xMnO yMn0 2.

The potassium salt, KMnO 4, may be prepared by passing chlorine or carbon dioxide through an aqueous solution of potassium manganate, or by the electrolytic oxidation of the manganate at the anode [German patent 101710 (1898)].

Barium Permanganate, BaMn 2 0 8, crystallizes in almost black needles, and is formed by passing carbon dioxide through water containing suspended barium manganate.

Manganese may be estimated quantitatively by precipitation as carbonate, this salt being then converted into the oxide, Mn 3 0 4 by ignition; or by precipitation as hydrated dioxide by means of ammonia and bromine water, followed by ignition to NIn 3 0 4.

Knowing that the water produced by the combustion of alcohol was not pre-existent in that substance but was formed by the combination of its hydrogen with the oxygen of the air, he burnt alcohol and other combustible organic substances, such as wax and oil, in a known volume of oxygen, and, from the weight of the water and carbon dioxide produced and his knowledge of their composition, was able to calculate the amounts of carbon, hydrogen and oxygen present in the substance.

It has strong basic properties, absorbs carbon dioxide readily, and forms welldefined crystalline salts.

This amidoguanidine decomposes on hydrolysis with the formation of semicarbazide, NH 2 CO NH NH 21 which, in its turn, breaks down into carbon dioxide, ammonia and hydrazine.

With water it is slowly converted into the dioxide.

Cerium dioxide, Ce02, is produced when cerium carbonate, nitrate, sulphate or oxalate is heated in air.

By suspending the precipitated cerous hydroxide in water and passing chlorine through the solution, a hydrated form of the dioxide, 2CeO 2.3H 2 O, is obtained, which is readily soluble in nitric and sulphuric acids, forming ceric salts, and in hydrochloric acid, where it forms cerous chloride, with liberation of chlorine.

Cerous chloride, CeC1 3, is obtained when the metal is burned in chlorine; when a mixture of cerous oxide and carbon is heated in chlorine; or by rapid heating of the dioxide in a stream of carbon monoxide and chlorine.

The sulphate, Ce(SO 4) 2.4H 2 O, is formed when the basic sulphate is dissolved in sulphuric acid; or when the dioxide is dissolved in dilute sulphuric acid, and evaporated in vacuo over sulphuric acid.

For the quantitative determination of the metal, the salts are precipitated by caustic potash, the precipitate washed, dried and heated, and finally weighed as the dioxide.

The object of the latter is to convert the manganous hydroxide by the atmospheric oxygen into manganese dioxide, but this would take place much too slowly if there was not an excess of lime present ready to combine with the manganese dioxide to form a calcium manganite.

There is only a slight mechanical loss, which is reduced in the best managed works to about parts of manganese dioxide to ioo of bleachingpowder.

For the manufacture of bleaching-powder, limestone of high degree of purity (especially free from magnesia and iron) is carefully burned so as to drive out nearly all the carbon dioxide without overheating the lime.

The former needs only grinding to constitute the final product, ammoniasoda ash; the latter is again employed in the process of treating the ammoniacal salt solution with carbon dioxide.

It begins, however, not with ready-made ammonium bicarbonate, but with the substances from which it is formed - ammonia, water and carbon dioxide - which are made to act on sodium chloride.

The ammoniacal salt solution is now saturated with carbon dioxide.

Just below the top there is a cooling arrangement, so that nearly all the water is condensed and runs back into the column, while the ammonia, with the carbon dioxide formerly combined with part of it, passes on first through an outside cooler where the remaining water is condensed, and afterwards into the vessels, already described, where the ammonia is absorbed by a solution of salt and thus again introduced into the process.

It combines with potassium to give (C 6 H 5) 3 CK, which with carbon dioxide gives potassium triphenylacetate, (C6H5)3C C02K.

Tungsten dioxide, W02, formed on reducing the trioxide by hydrogen at a red heat or a mixture of the trioxide and hydrochloric acid with zinc, or by decomposing the tetrachloride with water, is a brown strongly pyrophoric powder, which must be cooled in hydrogen before being brought into contact with air.

Partial reduction of tungsten trioxide gives blue or purple-red products which are intermediate in composition between the dioxide and trioxide.

The dichloride, WC1 2, is an amorphous grey powder obtained by reducing the hexachloride at a high temperature in hydrogen, or, better, by heating the tetrachloride in a current of carbon dioxide.

The tetrachloride, WC1 41 is obtained by partial reduction of the higher chlorides with hydrogen; a mixture of the pentaand hexa-chloride is distilled in a stream of hydrogen or carbon dioxide, and the pentachloride which volatilizes returned to the flask several times.

By passing bromine vapour over red-hot tungsten dioxide a mixture of WO 2 Br 2 and WOBr4 is obtained, from which the latter can be removed by gently heating when it volatilizes.

Ammonia does not react with tungsten or the dioxide, but with trioxide at a red heat a substance of the formula W 5 H 6 N 3 0 5 is obtained, which is insoluble in acids and alkalis and on ignition decomposes, evolving nitrogen, hydrogen and ammonia.

The manganese dioxide may be replaced by various other substances, such as red lead, lead dioxide, potassium bichromate, and potassium permanganate.

Besides the dryers already mentioned, lead acetate, manganese borate, manganese dioxide, zinc sulphate and other bodies are used.

Aqueous solutions of the acid are decomposed in sunlight by uranium salts, with evolution of carbon dioxide and the formation of propionic acid.

Potassium permanganate, in acid solution, oxidizes it to carbon dioxide and water.

It does not yield an anhydride, but when heated loses carbon dioxide and leaves a residue of propionic acid.

The decomposition is rendered more easy and regular by mixing the salt with powdered manganese dioxide.

The improved dioxide cyanide process was adopted about 1895.

Molten copper absorbs carbon monoxide, hydrogen and sulphur dioxide; it also appears to decompose hydrocarbons (methane, ethane), absorbing the hydrogen and the carbon separating out.

The gases are also expelled from the molten metal by lead, carbon dioxide, or water vapour.