Carbonate of the alkali

The chemists or alchemists gradually acquired a knowledge of the various salts produced by the action of acids on nitrum and of the transformations of the various salts from one form to another, by the action of acids on the different salts—e.g. sulphuric acid on sodium chloride. The carbonates of the alkalies were called mild alkalies to distinguish them from the caustic alkalies. It was known quite early that the caustic alkalies are obtained by the action of quicklime on the mild alkalies for example, the Latin Geber 7 and Albertus Magnus of the thirteenth century knew that the ash of plants furnished a caustic alkali when treated with quicklime and water. The process is essentially that employed to-day. 

In an important paper entitled Experiments upon magnesia alba) quicklime, and other alcaline substances, published in 1755,1 J. Black first made clear the relations between caustic alkali and mild alkali that is, between the alkali hydroxides and alkali carbonates. These relations were not understood by the early chemists. They believed the mild alkalies and alkaline earths—that is, the carbonates of the alkalies and alkaline earths—to be elementary substances that the causticity of lime was due to the union of fire-matter or phlogiston with elemental chalk and the conversion of mild alkali into caustic alkali, with the simultaneous regeneration of chalk, by boiling the former with caustic lime, was due simply to the transfer of the phlogiston or fire-matter from the lime to the mild alkali. Otherwise expressed Quicklime=Chalk-f Fire-matter. J. Black proved this hypothesis to be untenable. H. L. Duhamel du Monceau 2 had shown nine years earlier in a memoir Diverses experiences sur la chaux, that limestone loses weight when calcined and regains it little by little on exposure to air. 

Carbonates and Bi carbonates. Carbonates are the salts of carbonic acid and contain the C03= radical. Bicarbonates, also called acid carbonates, are salts contg the monovalent radical HC(>3-. All carbonates are readily decompd by acids carbonates of the alkali metals are sol in w, giving an alkaline reaction all others are insol in w (Ref 5,pp 168--9 Ref 7). Carbonates are formed by the action of C02 on a soln of alkali, but if excess of the gas is passed into the soln, a bicarbonate results. Bicarbonates are sol in water, and easily decompd by heat with the reformation of the normal carbonate... 

Most of the basic oxides may also be prepared by heating the carbonates, a class of salts afterwards to be discussed. The carbonates of the alkali metals, however, are not thus decomposed like their hydroxides, they may be volatilised without decomposition. But all other carbonates are decomposed by exposure to a red heat. The process has already been described as a method of manufacturing quicklime. Most carbonates, however, do not require the same high temperature a dull red heat suffices. And the oxides do not, as a rule, recombine with the carbon dioxide expelled, as does lime hence there is no danger of re-carbonating the oxide. 

The carbonates of the alkali metals are practically undecom-posable by heat alone. Compare the basic strength of the alkali metal oxides as a family with that of the alkaline earth oxides. 

The hydrogen carbonates of the alkali metals are soluble in water, but are less soluble than the corresponding normal carbonates. 

In the pure condition auric hydroxide resembles ferric hydroxide in appearance, and has the colour of brown ochre, but impurities impart to it a yellowish or greenish tint. It is soluble in nitric acid and hydrochloric acid, and in hot potassium-hydroxide solution, but insoluble in solutions of the carbonates of the alkali-metals and ammonium.6 It dissolves in solutions of the chlorides of sodium, potassium, and barium with production of complex salts.7 Prolonged heating at 140° to ISO0 C. eliminates all its water, with formation of auric oxide, Au2Oa. At 155° to 165° C. auric oxide is converted into gold monoxide, AuO.8... 

Corrosion and Ionisation.—Iron will remain untarnished for indefinite periods in the presence of concentrated solutions of the carbonates of the alkali metals, even in the presence of small quantities of other salts. If, however, the alkali carbonate is very dilute, it cannot entirely inhibit corrosion. Now, the minimum quantities of alkali carbonate required to inhibit the corrosive actions of a given concentration of various other salts of the same alkali metal have been determined.1 The results show that, if the added salts are arranged in order according to the amount of alkali carbonate required to inhibit corrosion, they are also not merely in the order of the relative strengths of their acid radicles, but the relative quantities of carbonate bear a general relationship to the numerical values found for the strengths of the acids by electrical conductivity methods. This is well illustrated in the following table —... 

PROP A term loosely applied to the hydroxides and carbonates of the alkali metals and alkaline earth metals, as well as the bicarbonate and hydroxide of ammonium. They can neutralize acids, change the color of indicators, and impart a soapy taste and feel to aq solns. 

Sodium hydroxide is not the only salt that will form these unstable compoimds with the trinitrotoluenes. Hepp (4) found that even the carbonates of the alkalies gave precipitations of a dark brown substance on the solution being treated with acid. He filtered this mixture, and on extracting the residue with ether obtained a small amount of an oil, which is probably a dinitrocresol. Later Hepp identified his substance, and proved conclusively that it was a dinitrocresol. 

A number of hydroxides and carbonates of the alkali and alkaline-earth metals have been used as catalysts for these reactions. Lobry de Bruyn and Alberda van Ekenstein considered the hydroxide ion to be responsible for their effect. Michaelis and Rona examined the transformation of D-glucose in several alkaline buffers and found that the re-... 

Carbonates of the alkalies act like the alkaline hydrate they give rise to the formation of the oxide and sulphides of the alkalies, with evolution of carbonic acid secondary actions produce siilphantimon-ites, antimonites, and antimony sulphide. The solution of the sulphide is never complete, even when it is heated and, according to Terreil, carbonate of potassium does not help it. This has been demonsti-ated by Weppen and affirmed by Terreil. When a solution of sodium carbonate, to which the sulphide has been added, is being cooled, there are formed the sulphide, neutral and acid antimonites of sodium, and antimonious acid, constituting what is called Kermes mineral. ... 

Foreign Bodies.—These are found by the usual methods, together with the chlorides, sulphates, and carbonates of the alkalies on the filter in 3. 

Alkali al-ko- lI [ME, fr. ML, from Arabic al-qili] (14c) n. Any of the hydroxides and carbonates of the alkali metals (lithium, sodium, and potassium), and the radical ammonium. The term is also used more... 

Solve (a) According to Table 4.1, most carbonates are insoluble, but carbonates of the alkali metal cations (such as sodium ion) are an exception to this rule and are soluble. Thus, Na2C03 is soluble in water. 

Chlorides, nitrates, and fluorides of all the metals are converted into carbonates, oxides, or the free metal by evaporating to dryness with oxalic acid, followed by ignition. After taking up the ignition residue in water, the filtrate will only react alkaline to litmus when either calcium oxide or the carbonates of the alkali metals are present. If the ignition with oxalic acid is followed by treatment with ammonium carbonate to convert any calcium oxide to carbonate, then, after elimination of (NH4)2C03, a basic reaction to litmus indicates alkali metals. 

These uonnal carbonates of the alkali-nietaJs are salable in water, and have an alkaline reaction When they arc treated with an excess of carbon dioxide, the solution becomes neutral aud then contains an add carbonate —... 

Other conditioning agents that may be used instead of sodium hydroxide are such bases as the carbonates of the alkali metals or of ammonia, pyridine, or ethanolamine [56]. 

An undesirable side reaction is carbonation of the alkali by the CO2 evolved, which involves the equilibrium... 

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