Alkaline-earth-metal Sulphates

BeS04 is observed, and thermal dissociation takes place without a fusion sta. An equation for the dissociation pressure of BeS04 in the temperature range 650—850 C was derived and an activation energy of 47 kcal mol obtained. 

Kocova and V, Vaclava, Coll. Czech. Chem. Comm., 1972, 37, 3669. 

Matsuzaki, M. Setaka, U. V. Gromov, and T. Kwan, Bull. Chem. Soc. Japan, 1972, 

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For the most part it is true to say that the chemistry of the alkali and alkaline earth metal compounds is not that of the metal ion but rather that of the anion with which the ion is associated. Where appropriate, therefore, the chemistry of these compounds will be discussed in other sections, for example nitrates with Group V compounds, sulphates with Group VI compounds, and only a few compounds will be discussed here. 

The sulphates of the alkali and alkaline earth metals and man-ganese(II) are stable to heat those of heavier metals decompose on heating, evolving sulphur trioxide and leaving the oxide or the metal ... 

Alkali and Alkaline Earth Metals are determined as sulphate. Weigh the substance in a quartz or platinum crucible, add a few drops of concentrated (for explosive or unstable substances use 30-50 per cent acid) sulphuric add and evaporate cautiously. Finally ignite at dull red heat. 

Sulphates of the alkali and alkaline earth metals, when heated with sulphur, are converted into sulphide, polysulphide and thiosulphate, with simultaneous formation of sulphur dioxide many other sulphates, e.g. those of copper, mercury, silver and lead, yield only sulphide.7 Other salts of the metals behave in a similar- manner, undergoing transformation into sulphides, the change being effected more readily with the salts of the heavy metals, many of which indeed react slowly with sulphur even at 100° C. in the presence of water.8 At 150° to 200° C. mercuric, stannic and ferric salts in aqueous solution are quantitatively reduced by sulphur mercurous, cupric, bismuth and lead salts arc slowly but quantitatively precipitated as sulphides. Nitrates, permanganates and iodates cause oxidation of the sulphur to sulphuric acid. 

In the case of the alkali and alkaline earth metals, the sulphate is the sole product with copper, lead, bismuth and antimony, the product contains the metal, formed by reduction of the sulphate by unchanged sulphide. In cases where the sulphate is unstable at the temperature of reaction, as with zinc, cadmium, aluminium, tin, chromium, iron, cobalt and nickel, the oxide is the final product. The action may be catalytically accelerated by the addition of triferric tetroxide, Fe304.2... 

For solutions containing sulphuric acid or a sulphate the reagent commonly applied is barium chloride, both when the test is to be qualitative and when quantitative. Precipitation is effected by the gradual addition of barium chloride to the boiling solution containing a little hydrochloric acid, but for the production of pure barium sulphate, and therefore in order to ensure accuracy, certain precautions must be observed.4 Nitrates, perchlorates, phosphates, tervalent metals and large quantities of salts of the alkali metals (particularly potassium) and of the alkaline earth metals are to be avoided, as they cause the precipitated barium sulphate to be rendered impure by occlusion of otherwise soluble substances.5 Such impurities may be accounted for partly by... 

Of the dithionates, those of the alkali and alkaline earth metals are the most stable and may be heated in aqueous solution up to 100° C. without decomposition. When heated alone, the dithionates decompose readily with formation of sulphate and sulphur dioxide some of them indeed are so unstable that they are not obtainable in a pure condition. 

Sulphates of the alkali- and alkaline-earth metals are stable at all temperatures lower than that of the electric arc but all other sulphates decompose, the primary product being the oxide of the metal and sulphuric anhydride the latter, however, being unstable at a red-heat, decomposes partly into sulphur dioxide and free oxygen. This decomposition is made use of in the preparation of Nordhausen sulphuric acid, a fuming liquid, consisting chiefly of H2S207 it is made by distilling partially dried ferrous sulphate from fireclay retorts 2 Fe S 04 = Fe2 Oa + S 02 + S 03 the... 

Derivatisation-electron capture gas chromatography has been used to determine pg L 1 quantities of nitrite in water without interference from halides, nitrate, phosphate, sulphate, bicarbonate, ammonium and alkali metals and alkaline earth metals [792],... 

The alkaline earth metals are divalent their hydroxides, M(OH)2, are less soluble than those of the alkali metals, but are nevertheless very strongly basic. The compounds of these metals are not so generally soluble as those of the alkali metals, and in particular the carbonates, sulphates, and phosphates are mostly insoluble. 

At first sight it would seem that the decomposition voltages of neutral solutions of sulphates and nitrates of alkali metals and alkaline-earth metals should also be in the region of 1.7 V. Aotually the respective values are higher. 

The sodium soap is soluble in water and a very small quantity suflices to produce a lather if the water is pure. If, however, it contains dissolved salts of calcium or magnesium the lather is destroyed by these, yielding the familiar insoluble curd, so characteristic of the action of hard water on soap. This curd is really the insoluble soap of the alkaline earth metal formed by double decomposition as shown in the two following equations, in which it is assumed the hardness is due to the presence of calcium carbonate and magnesium sulphate respectively. ... 

The same order holds for the decomposition of the sulphates those of the trivalent elements aluminium and iron decompose relatively easily, those of the alkaline earth metals decompose appreciably on heating to redness (thus CaS04 decomposes quantitatively on ignition in the blowpipe flame, barium sulphate only a little), the alkali sulphates are stable. That the free acids are much less stable than most of the salts is understandable when we regard the hydrogen ion as an extremely small positive ion. 

The three alkaline earth metals decompose water at different rates, forming hydroxides and hydrogen gas. Their hydroxides are strong bases, although with different solubilities barium hydroxide is the most soluble, while calcium hydroxide is the least soluble among them. Alkaline earth chlorides and nitrates are very soluble the carbonates, sulphates, phosphates, and oxalates are insoluble. The sulphides can be prepared only in the dry they all hydrolyse in water, forming hydrogen sulphides and hydroxides, e.g. 

The metal can be estimated as chloride or sulphate, or by heating the sulphate with sulphuric acid and the sulphate of an alkaline-earth metal such as calcium, a double sulphate of the type Rb2S04,CaS04 being formed and weighed.4... 

The potassium salt is the most soluble, whilst the caesium salt is quite insoluble in water. Both the rubidium and the caesium salts may be prepared by double decomposition of dilute solutions of their chlorides with the nitroso salts of sodium or potassium. The thallium salt may be prepared in a similar manner by means of thallium sulphate. The nitroso salts of the alkaline earth metals—calcium, barium, and magnesium—are very soluble in water. 

SHE] Shehata, H. A., Studies of formation of some metal(Il) sulphate complex using conductometry technique. I- Bivalent ions of the first transition series and alkaline earth metals in aqueous media at 25 C, Ultra Sci. Phys. Sci, 5, (1993), 108-113. Cited on pages 181, 184, 185,426. 

Atomic spectrometric tests in air/acetylene flames a number of ions (like phosphate, sulphate, aluminium) decrease the emission and absorption signals of barium (and all of the alkaline earth metals). Adding an equal volume of a 25% solution of lanthanum chloride heptahydrate LaCl3 7H2O eliminates these interferences. Addition of lanthanum is not required if the nitrous oxide/acetylene flame is used. 

Alkaline-earth metal sulphides have been prepared by hydrogen reduction of the metal sulphate at high temperatures. Calcium sulphate was reduced at >850 °C, with strontium and barium sulphates being reduced at >950 °C. The products of the reduction were said to be imiform and to contain about 98% sulphide. A method has been described by which the sulphides CaS, SrS, and BaS may be prepared by the reaction of the metals in solution in liquid ammonia with an excess of hydrogen sulphide at temperatures ranging from —78 to —33 °C in high vacuum. Analytical data and lattice parameters of the sulphides prepared in this way were given. 

B. Courtois, an entrepreneur from the French town of Dijon, was engaged, among other things, in the production of potash and saltpeter. He used ash of sea algae as the initial raw material. A mother solution of sea algae was formed under the action of water on the ash. To-day we know that the ash contains chlorides, bromides, iodides, carbonates, and sulphates of some alkali and alkaline-earth metals. However, when Courtois performed his experiments it was only known that the ash contained potassium and sodium compounds (chlorides, carbonates, and sulphates). Upon evaporation, first, sodium chloride precipitated and then potassium chloride and sulphate. The residual mother solution contained a complex mixture of various salts, including sulphur-containing ones. 

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