Barium Sentence Examples

The next group may contain the white calcium, barium and strontium carbonates.

Beryllium and magnesium are permanent in dry air; calcium, strontium and barium, however, oxidize rapidly on exposure.

The metals comprising this group are never found in the uncombined condition, but occur most often in the form of carbonates and sulphates; they form oxides of the type RO, and in the case of calcium, strontium and barium, of the type R02.

In 1808 Davy isolated sodium and potassium; he then turned his attention to the preparation of metallic calcium, barium, strontium and magnesium.

The barium and magnesium salts of this acid are formed when baryta and magnesia are fused with cobalt sesquioxide.

Barium chloride is present in some natural waters, and when this is the case the interaction of sulphates results in a deposition of barytes, as has occurred in the pipes and water-boxes of the Newcastle-on-Tyne coal mines.

Commercially, barytes is used in the preparation of barium compounds, as a body for certain kinds of paper and cloth, and as a white pigment ("permanent white").

Ammonium carbonate is added to the filtrate; this precipitates calcium, strontium and barium.

An immediate precipitate indicates barium; a precipitate on standing indicates strontium.

The solution free from barium is treated with ammonia and ammonium sulphate, which precipitates strontium, and the calcium in the solution may be identified by the white precipitate with ammonium oxalate.

Horbaczewski's method, which consists in boiling the substance with strong potash, saturating the cold solution` with chlorine, adding hydrochloric acid, and boiling till no more chlorine is liberated, and then testing for sulphuric acid with barium chloride.

Neumann, who, in 1831, deduced from observations on many carbonates (calcium, magnesium, ferrous, zinc, barium and lead) that stoichiometric quantities (equimolecular weights) of compounds possess the same heat capacity.

Most of the rubber now manufactured is not combined with sulphur when in the form of sheets, but is mechanically incorporated with about one-tenth of its weight of that substance by means of the mixing rollers - any required pigment or other matter, such as whiting or barium sulphate, being added.

They are silicates, usually orthosilicates, of aluminium together with alkalis (potassium, sodium, lithium, rarely rubidium and caesium), basic hydrogen, and, in some species magnesium, ferrous and ferric iron, rarely chromium, manganese and barium.

Venetian white, Hamburg white and Dutch white are mixtures of one part of white lead with one, two and three parts of barium sulphate respectively.

Ammonium sulphide blackens it, and it is soluble in solution of ammonium acetate, which distinguishes it from barium sulphate.

Four miles lower down the Irfon valley, at the junction of the Cammarch and Irfon, and with a station on the London & North Western railway, is the village of Llangammarch, noted for its barium springs.

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.

The newer glasses, on the other hand, contain a much wider variety of chemical constituents, the most important being the oxides of barium, magnesium, aluminium and zinc, used either with or without the addition of the bases already named in reference to the older glasses, and - among acid bodies - boric anhydride (B20 3) which replaces the silica of the older glasses to a varying extent.

The materials employed are sand, sulphate of soda, nitrate of soda, calcspar and in some works carbonate of barium.

Silicofluoric acid, H2SiF6, is obtained as shown above, and also by the action of sulphuric acid on barium silicofluoride, or by absorbing silicon fluoride in aqueous hydrofluoric acid.

Many are found as minerals, the more important of such naturally occurring carbonates being cerussite (lead carbonate, PbC03), malachite and azurite (both basic copper carbonates), calamine (zinc carbonate, ZnCO 3), witherite (barium carbonate, BaCO 3), strontianite (strontium carbonate, SrC03), calcite (calcium carbonate, CaC03), dolomite (calcium magnesium carbonate, CaCO 3 MgCO 3), and sodium carbonate, Na 2 CO 3.

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

Water, at ordinary or slightly elevated temperatures, is decomposed more or less readily, with evolution of hydrogen gas and formation of a basic hydrate, by (I) potassium (formation of KHO), sodium (NaHO), lithium (LiOH), barium, strontium, calcium (BaH 2 O 2, &c.); (2) magnesium, zinc, manganese (MgO 2 H 2, &c.).

Somewhat less volatile than the last-named group are the chlorides (MC1 2) of barium, strontium and calcium.

Barium and strontium have also been produced by electrometallurgical methods, but the processes have only a laboratory interest at present.

Aqueous alcohol becomes turbid when mixed with benzene, carbon disulphide or paraffin oil; when added to a solution of barium oxide in absolute alcohol, a white precipitate of barium hydroxide is formed.

At the same time any lead, calcium, barium and strontium present are precipitated as sulphates; it is therefore advantageous to remove these metals by the preliminary addition of sulphuric acid, which also serves to keep any basic iron salts in solution.

Rohrbach's solution, an aqueous solution of barium and mercuric iodides, introduced by Carl Rohrbach, has a density of 3.588.

The free acid may be obtained by decomposing the barium salt with sulphuric acid and concentrating the solution, when a crystalline mass of composition H 2 Te04.2H 2 O separates.

In a smaller degree these alkaline properties are shared by the less soluble hydrates of the "metals of the alkaline earths," calcium, barium and strontium, and by thallium hydrate.

The residue so obtained is then powdered and ignited with barium nitrate, which converts the iridium into its oxide and the osmium into barium osmiate.

The barium salt is extracted by water and boiled with nitric acid, when the osmium volatilizes in the form of its tetroxide.

As an alternative the osmiridium is fused with zinc, the regulus treated with hydrochloric acid, and then heated with barium nitrate and barium peroxide.

After fusion, the mass is finely powdered and treated with cold dilute hydrochloric acid; and when action has finished, nitric and sulphuric acids are added, the precipitated barium sulphate removed, the liquid distilled and the osmium precipitated as sulphide.

Ammonium chlorate, NH 4 C10 3, is obtained by neutralizing chloric acid with either ammonia or ammonium carbonate, or by precipitating barium, strontium or calcium chlorates with ammonium carbonate.

Ammonium nitrite, NH 4 NO 2, is formed by oxidizing ammonia with ozone or hydrogen peroxide; by precipitating barium or lead nitrites with ammonium sulphate, or silver nitrite with ammonium chloride.

The iodides can be prepared either by direct union of iodine with a metal, from hydriodic acid and a metal, oxide, hydroxide or carbonate, or by action of iodine on some metallic hydroxides or carbonates (such as those of potassium, sodium, barium, &c.; other products, however, are formed at the same time).

Iodic Acid, H10 3, can be prepared by dissolving iodine pentoxide in water; by boiling iodine with fuming nitric acid, 61+10HN03= 6H10 3 +10N0+2H 2 O; by decomposing barium iodate with the calculated quantity of sulphuric acid, previously diluted with water, or by suspending iodine in water and passing in chlorine, 12+5C12+ 6H 2 0=2H10 3 +10HC1.

The free acid forms dark red deliquescent crystals and is obtained by decomposing the silver salt with hydrochloric acid, or the barium salt with dilute sulphuric acid.

Normal chromates on the addition of silver nitrate give a red precipitate of silver chromate, easily soluble in ammonia, and with barium chloride a yellow precipitate of barium chromate, insoluble in acetic acid.

In the spectrum of barium no series has yet been recognized.

It may be purified by redistillation over barium and silver nitrates, followed by treatment of the distillate with a stream of ozonized air.

To purify the oxide, it is dissolved in dilute hydrochloric acid until the acid is neatly neutralized, the solution is cooled, filtered, and baryta water is added until a faint permanent white precipitate of hydrated barium peroxide appears; the solution is now filtered, and a concentrated solution of baryta water is added to the filtrate, when a crystalline precipitate of hydrated barium peroxide, Ba0 2 8 H 2 0, is thrown down.

The solution is filtered, and the barium precipitated by sulphuric acid.

The ester is separated from the solution by means of its barium salt, and the salt decomposed by the addition of the calculated amount of sulphuric acid.

After removing the uranium, it was found that the bismuth separated with a very active substance - polonium; this element was afterwards isolated by Marckwald, and proved to be identical with his radiotellurium; that the barium could be separated with another active substance - radium; whilst a third fraction, composed mainly of the rare earths (thorium, &c.), yielded to Debierne another radioactive element - actinium, which proved to be identical with the emanium of Giesel.

There is a mass of evidence to show that radium is to be regarded as an element, and in general its properties resemble those of the metals of the alkaline earths, more particularly barium.

To the bunsen flame a radium salt imparts an intense carmine-red colour (barium gives a green).

The nitrate Be(NO,)2.3H20 is prepared by adding barium nitrate to ber y llium sulphate solution; it crystallizes with difficulty and is very deliquescent.

The precipitate is dissolved in boiling water, decolorized by potassium permanganate and decomposed by barium carbonate.

This acid is also formed by decomposing barium or lead permanganate with dilute sulphuric acid.

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

The gallium salts are precipitated by alkaline carbonates and by barium carbonate, but not by sulphuretted hydrogen unless in acetic acid solution.

A peroxide, N102, has been obtained in the form of dinickelite of barium, BaO.

Metatungstic acid, H2W4013.7H20, is obtained by decomposing the barium salt with sulphuric acid or the lead salt with hydrochloric acid.

Berthollet, and is best prepared by decomposing barium chlorate with the calculated amount of dilute sulphuric acid.

Barium does not seem to have been a place of great importance in early antiquity; only bronze coins struck by it have been found.

In Roman times it was the point of junction between the coast road and the Via Traiana; there was also a branch road to Tarentum from Barium.

Succinic anhydride, C 2 H 4 (CO) 2 0, is obtained by heating the acid or its sodium salt with acetic anhydride; by the action of acetyl chloride on the barium salt; by distilling a mixture of succinic acid and succinyl chloride, or by heating succinyl chloride with anhydrous oxalic acid.

These alkyl substitution products are important, for they lead to the synthesis of many organic compounds, on account of the fact that they can be hydrolysed in two different ways, barium hydroxide or dilute sodium hydroxide solution giving the socalled ketone hydrolysis, whilst concentrated sodium hydroxide gives the acid hydrolysis.

Barium occurs chiefly in the form of barytes or heavy spar, BaS 04, and witherite, BaCO 3, and to a less extent in baryto-calcite, baryto-celestine, and various complex silicates.

Davy tried to electrolyse baryta, but was unsuccessful; later attempts were made by him using barium chloride in the presence of mercury.

In this way he obtained an amalgam, from which on distilling off the mercury the barium was obtained as a silver white residue.

Bunsen in 1854 electrolysed a thick paste of barium chloride and dilute hydrochloric acid in the presence of mercury, at 10o C., obtaining a barium amalgam, from which the mercury was separated by a process of distillation.

Guntz (Comptes rendus, 1901, 133, p. 872) electrolyses a saturated solution of barium chloride using a mercury cathode and obtains a 3% barium amalgam; this amalgam is transferred to an iron boat in a wide porcelain tube and the tube slowly heated electrically, a good yield of pure barium being obtained at about looo C. The metal when freshly cut possesses a silver white lustre, is a little harder than lead, and is extremely easily oxidized on exposure; it is soluble in liquid ammonia, and readily attacks both water and alcohol.

Three oxides of barium are known, namely, the monoxide, BaO, the dioxide, Ba02, and a suboxide, obtained by heating Ba0 with magnesium in a vacuum to 110o (Guntz, loc. cit., 1906, p. 359).

Barium hydroxide, Ba(OH) 2, is a white powder that can be obtained by slaking the monoxide with the requisite quantity of water, but it is usually made on the large scale by heating heavy spar with small coal whereby a crude barium sulphide is obtained.

This sulphide is then heated in a current of moist carbon dioxide, barium carbonate being formed, BaS+H 2 O+CO 2 =BaCO 3 +H 2 S, and finally the carbonate is decomposed by a current of superheated steam, BaC03+H20 = Ba(OH) 2 + C02, leavingaresidue of the hydroxide.

In the Brin process for the manufacture of oxygen, barium dioxide is obtained as an intermediate product by heating barium monoxide with air under pressure.

Barium chloride, BaCl 2.2H 2 O, can be obtained by dissolving witherite in dilute hydrochloric acid, and also from heavy spar by ignition in a reverberatory furnace with a mixture of coal, limestone and calcium chloride, the barium chloride being extracted from the fused mass by water, leaving a residue of insoluble calcium sulphide.

Barium bromide is prepared by saturating baryta-water or by decomposing barium carbonate with hydrobromic acid.

It crystallizes as BaBr 2.2H 2 O isomorphous with barium chloride.

Barium bromate, Ba(Br03)2, can be prepared by the action of excess of bromine on barytawater, or by decomposing a boiling aqueous solution of loo parts of potassium bromate with a similar solution of 74 parts of crystallized barium chloride.

It can also be obtained by suspending barium carbonate in boiling water and passing in chlorine.

Barium carbide, BaC2, is prepared by a method similar to that in use for the preparation of calcium carbide (see Acetylene).

Maquenne has also obtained it by distilling a mixture of barium amalgam and carbon in a stream of hydrogen.

Barium sulphide, BaS, is obtained by passing sulphuretted hydrogen over heated barium monoxide, or better by fusion of the sulphate with a small coal.

Barium nitride, Ba 3 N 2, is obtained as a brownish mass by passing nitrogen over heated barium amalgam.

Barium amide, Ba(NH 2) 2, is obtained from potassammonium and barium bromide.

Barium nitrate, Ba(N03)2, is prepared by dissolving either the carbonate or sulphide in dilute nitric acid, or by mixing hot saturated solutions of barium chloride and sodium nitrate.

Barium carbonate, BaCO 31 occurs rather widely distributed as witherite, and may be prepared by the addition of barium chloride to a hot solution of ammonium carbonate, when it is precipitated as a dense white powder of specific gravity 4.3; almost insoluble in water.

Barium and its salts can be readily detected by the yellowishgreen colour they give when moistened with hydrochloric acid and heated in the Bunsenflame, or by observation of their spectra, when two characteristic green lines are seen.

In solution, barium salts may be detected by the immediate precipitate they give on the addition of calcium sulphate (this serves to distinguish barium salts from calcium salts), and by the yellow precipitate of barium chromate formed on the addition of potassium chromate.

Barium is estimated quantitatively by conversion into the sulphate.

It combines with chlorides of the alkali metals to form double salts, and also with barium, calcium, strontium, and magnesium chlorides.

The barium carbonate used in the process acts as a contact substance, since the temperature at which the operation is carried out is always above the decomposition point of barium acetate.

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.

Its salts, the selenates, are obtained by the oxidation of the selenites, and the free acid may be obtained by the decomposition of the lead or barium salt.

The fused mass separates into two layers, the upper of which contains a mixture of potassium and lithium sulphates; this is lixiviated with water and converted into the mixed chlorides by adding barium chloride, the solution evaporated and the lithium chloride extracted by a mixture of dry alcohol and ether.

The distillate was further purified by digestion with milk of lime, precipitation with water, and further digestion with calcium bromide and barium oxide, and was finally redistilled.

Bromic acid is obtained by the addition of the calculated amount of sulphuric acid (previously diluted with water) to the barium salt; by the action of bromine on the silver salt, in the presence of water, 5AgBrO, 3Br 2 3H 2 O = 5AgBr 6HBrO 3, or bypassing chlorine through asolution of bromine in water.

Hypophosphorous acid, HP(OH) 2, discovered by Dulong in 1816, and obtained crystalline by Thomson in 1874 (Ber., 7, P. 994), is prepared in the form of its barium salt by warming phosphorus with baryta water, removing the excess of baryta by carbon dioxide, and crystallizing the filtrate.

The acid may be prepared by evaporating in a vacuum the solution obtained by decomposing the barium salt with the equivalent amount of sulphuric acid.

It is not found in nature in the free state to any extent, and although enormous quantities of its salts, especially calcium and barium sulphate, are found in many localities, the free acid is never prepared from these salts, as it is more easily obtainable in another way, viz.

As a general class, the sulphates are soluble in water, and exhibit well crystallized forms. Of the most insoluble we may notice the salts of the metals of the alkaline earths, barium, strontium and calcium, barium sulphate being practically insoluble, and calcium sulphate sparingly but quite appreciably soluble.

In solution, sulphates are always detected and estimated by the formation of a white precipitate of barium sulphate, insoluble in water and all the common reagents.

Barium ferrate, BaFeO4H20, obtained as a dark red powder by adding barium chloride to a solution of potassium ferrate, is fairly stable.

Ferrous nitrate, Fe(NO3)2.6H2O, is a very unstable salt, and is obtained by mixing solutions of ferrous sulphate and barium nitrate, filtering, and crystallizing in a vacuum over sulphuric acid.

The barium salt (+6H 2 0) is very soluble (a distinction between phthalic and terephthalic acids).

Among the less important Spanish minerals are manganese (chiefly in Ciudad Real), antimony, gold, cobalt, sodic sulphate, sulphate of barium (barytes), phosphorite (found in Chceres), alum, sulphur, kaolin, lignite, asphalt, besides a variety of building and ornamental stones.

The chromates are stable towards heat; they are poisonous, and may be recognized by the yellow precipitates they give with soluble barium and lead salts.

Similar sodium, ammonium, lithium, magnesium, calcium, barium and zinc salts have been obtained.

Baryte contains the chemical element barium, which is heavier than the calcium, in gypsum.

Barium examinations are a common test using this method which shows up the digestive system with the use of a liquid called barium examinations are a common test using this method which shows up the digestive system with the use of a liquid called barium.

Your child will usually be asked to drink barium.

My brother was given a barium swallow a month ago.

Diagnosis is usually made with barium X-rays (taken after the patient swallows barium liquid to show up the inside of the intestine ).

The contraption, however, held none of the promise of his discovery of glowing barium.

Evaluation techniques include clinical assessment and modified barium swallow procedure.

At that time he was interested in the then relatively new technique of the double contrast barium enema.

Uncertainty of diagnosis (ie more investigations required Eg barium studies, sigmoidoscopy, etc ).

A small bowel barium study was performed via the jejunostomy.

The task could be broadened to cover other heavy metals including cadmium & barium.

Potentially these could include cardiac MRI scans and small bowel scanning which might provide an alternative to barium meals.

The rectal balloon catheter used for barium enema can very rarely cause perforation.

They will consist of some form of endoscopic examination (either sigmoidoscopy or colonoscopy ), often followed by a barium enema radiological examination.

If complete colonoscopy is not feasible, flexible sigmoidoscopy followed by a double-contrast barium enema is an acceptable alternative.

A barium follow-through examination may show a terminal ileal or colonic stricture.

The ceramic is a fine-grained mixture including barium titanate and similar materials with a high permittivity.

He noticed that while the rays were being produced, a screen coated in fluorescent barium platinocyanide would glow.

Another screening technique is barium radiology in which the patient swallows barium liquid that shows the inside of the stomach on X-ray.

His turquoise glazes are obtained by using barium carbonate mixed with soda, feldspar and nepheline syenite.

The family of ferroelectric ceramic materials such as barium titanate and lead zirconate titanate (PZT) were developed in the 1940s.

The barium sulfate is highly insoluble and the very heavy barium atoms are very effective at scattering X-radiation.

It was amazing, tho, for me to see my equipment at work, as I could with the barium X-ray.

Quicklime, barium oxide, and dehydrated copper sulphate are especially applicable to alcohol and ether; the last traces of water may be removed by adding metallic sodium and distilling.

In this process the osmiridium is fused with zinc and the excess of zinc evaporated; the residue is then ignited with barium nitrate, extracted with water and boiled with nitric acid.

If the hot colourless bead becomes enamel-white on cooling even when minute quantities of the substances are employed, we may infer the presence of barium or strontium.

Sodium gives an intense and persistent yellow flame; lithium gives a carmine coloration, and may be identified in the presence of sodium by viewing through a cobalt glass or indigo prism; from potassium it may be distinguished by its redder colour; barium gives a yellowishgreen flame, which appears bluish-green when viewed through green glass; strontium gives a crimson flame which appears purple or rose when viewed through blue glass; calcium gives an orange-red colour which appears finch-green through green glass; indium gives a characteristic bluish-violet flame; copper gives an intense emerald-green coloration.

Chem., 1866, 9 8, p. 340); by the action of chlorine on steam at a bright red heat; by the decomposition of hydrogen peroxide by bleaching powder, manganese dioxide, potassium ferricyanide in alkaline solution, or potassium permanganate in acid solution; by heating barium peroxide with an aqueous solution of potassium ferricyanide (G.

When digested with fuming hydrochloric acid for some time it is converted into ad furfurane dicarboxylic acid (see Furfurane); while on heating with barium sulphide it is transformed into a - thiophene carboxylic acid (see Thiophene).

Barium sulphate, BaSO 4, is the most abundant of the naturally occurring barium compounds (see Barytes) and can be obtained artificially by the addition of sulphuric acid or any soluble sulphate to a solution of a soluble barium salt, when it is precipitated as an amorphous white powder of specific gravity 4.5.

These include barium sulfate and strontium sulfate which produce colored effects when ignited.

It was amazing, tho, for me to see my equipment at work, as I could with the barium x-ray.

Instead, the HTS crystals (made from yttrium barium copper oxide) react individually when they approach the rotor 's permanent magnets.

In order to increase the information obtained from a conventional x ray, air or contrast media (such as barium or iodine) may be used to enhance the images.

Contrast agent-Also called a contrast medium, this is usually a barium or iodine dye that is injected into the area under investigation.

Because this liquid has usually been barium, a metallic, chalky substance, the upper GI series is sometimes called a barium swallow.

X rays or images are then taken as the barium flows down the esophagus, into the stomach, and into the duodenum.

The child may be asked to turn on his or her side so that the technician can gently massage the stomach to move the barium into the duodenum.

Sometimes a liquid called contrast material (for example, barium) is used to help outline internal organs such as the intestines.

The x ray images may be enhanced by giving the child a barium enema, a form of contrast or opaque media that allows more detail to be seen in x rays and MRI or CT scans.

In a barium enema, barium sulfate is infused through the rectum and the intestinal area is scanned.

Sometimes a lighted, flexible fiber optic instrument (sigmoidoscope) may be inserted rectally in conjunction with a barium enema to visualize the bowel.

In infants, a barium enema may reverse intussusception in 50-90 percent of cases.

An air enema is sometimes used instead of a barium or gastrografin enema.

It may be necessary to do more invasive tests, such as a barium enema or upper GI series, if the obstruction is mechanical.

Barium studies are used in cases of mechanical obstruction but may cause problems by increasing pressure or intestinal contents if used in ileus.

Also, in cases of suspected mechanical obstruction involving the gastrointestinal tract (from the small intestine downward) use of barium x rays are contraindicated, since they may contribute to the obstruction.

In such cases a barium enema should always be done first.

Diagnostic tests may include stool or blood tests, hydrogen breath test, or an x ray of the bowel, called a barium enema.

Barium enema-An x ray of the bowel using a liquid called barium to enhance the image of the bowel.

When symptoms continue even after treatment or to rule out the presence of other illnesses with similar symptoms, the diagnostic evaluation may include blood tests, a hydrogen breath test, or an x ray of the bowel, called a barium enema.

Barium studies can reveal mucosal edema and thickening of the small intestinal wall in EC and ED.

The diagnosis is confirmed by a barium enema x ray, which shows a picture of the bowel.

Barium enema-An x-ray procedure that involves the administration of barium into the intestines by a tube inserted into the rectum.

Barium is a chalky substance that enhances the visualization of the gastrointestinal tract on x ray.

The most common of these sulphides is cobaltous sulphide, CoS, which occurs naturally as syepoorite, and can be artificially prepared by heating cobaltous oxide with sulphur, or by fusing anhydrous cobalt sulphate with barium sulphide and common salt.

Wehnelt discovered that the same effect could be produced by using instead of a carbon filament a platinum wire covered with the oxides of calcium or barium, which when incandescent have the property of copiously emitting negative ions.

From Beneventum, another important road centre, the Via Appia itself ran south-east through the mountains past Venusia to Tarentum on the south-west coast of the heel, and thence across Calabria to Brundusium, while Trajans correction of it, following an older mule-track, ran north-east through the mountains and then through the lower ground of Apulia, reaching the coast at Barium.

The road along the east coast from Fanum Fortmrnae down to Barium, which connected the terminations of the Via Salaria and Via Valeria, and of other roads farther south crossing from Campania, had no special name in ancient times, as far as we know.

The so-called alkaline earth-metals are the elements beryllium, magnesium, calcium, strontium and barium.

The acid is considered to possess the structure 0 2 S(SH) (OH), since sodium thiosulphate reacts with ethyl bromide to give sodium ethyl thiosulphate, which on treatment with barium chloride gives presumably barium ethyl thiosulphate.

This salt, on standing, decomposes into barium dithionate, BaS206, and diethyl disulphide, (C2H5)2S2, which points to the presence of the SH group in the molecule.

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.

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.

The free acid is obtained (in dilute aqueous solution) by the addition of dilute sulphuric acid to an aqueous solution of the barium salt.

Artificially prepared crystals of barytes may be obtained by allowing a solution of a soluble barium salt to diffuse slowly into a solution of a soluble sulphate.

If barium is present, the solution of the carbonates in hydrochloric acid is evaporated and digested with strong alcohol for some time; barium chloride, which is nearly insoluble in alcohol,is thus separated, the remainder being precipitated by a few drops of hydrofluosilicic acid, and may be confirmed by the ordinary tests.

It is, in fact, admitted that some of the glasses, most useful optically, the dense barium crown glasses, which are so widely used in modern photographic lenses, cannot be produced entirely free either from noticeable colour or from numerous small bubbles, while the chemical nature of these glasses is so sensitive that considerable care is required to protect the surfaces of lenses made from them if serious tarnishing is to be avoided.

In its chemical properties it closely resembles barium and strontium, and to some degree magnesium; these four elements comprise the so-called metals of the "alkaline earths."

The oxides of lead, barium, zinc and antimony are found perceptibly to retard the rays.