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.
Heated with sulphuric acid and with nitric acid it is oxidized to boric acid, whilst on fusion with alkaline carbonates and hydroxides it gives a borate of the alkali metal.
In Western Australia the lead occurs in the form of sulphides and carbonates of great richness, but the quantity of silver mixed with it is very small.
Zinc ores, in the several varieties of carbonates, silicates, oxide, sulphide and sulphate of zinc, have been found in several of the Australian states, but have attracted little attention except in New South Wales, where special efforts are being made successfully to produce a high-grade zinc concentrate from the sulphide ores.
Normal cadmium carbonates are unknown, a white precipitate of variable composition being obtained on the addition of solutions of the alkaline carbonates to soluble cadmium salts.
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.
The salts of all the metals of this group usually crystallize well, the chlorides and nitrates dissolve readily in water, whilst the carbonates, phosphates and sulphates are either very sparingly soluble or are insoluble in water.
Germanium compounds on fusion with alkaline carbonates and sulphur form salts known as thiogermanates.
The sulphites are prepared by the action of sulphur dioxide on the oxides, hydroxides or carbonates of the metals, or by processes of precipitation.
Sodium carbonates), and with herds of cattle and sheep, receiving in return cotton and hardware and kolas; (4) the Hausa merchants.
It is a strong acid, and dissolved in water decomposes carbonates and attacks iron and zinc.
Iron and quinine citrate is used as a bitter stomachic and tonic. In the blood citrates are oxidized into carbonates; they therefore act as remote alkalis, increasing the alkalinity of the blood and thereby the general rate of chemical change within the body (see Acetic Acid).
The manufacture of glass, also practised in Egypt, demanded a knowledge of sodium or potassium carbonates; the former occurs as an efflorescence on the shores of certain lakes; the latter was obtained from wood ashes.
Carbon dioxide, recognized by turning lime-water milky, indicates decomposable carbonates or oxalates.
The carbonates are dissolved in hydrochloric acid, and calcium sulphate solution is added to a portion of the solution.
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.
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.
Calcium carbonate separates as hexagonal calcite from cold solutions (below 30°), and as rhombic aragonite from solutions at higher temperatures; lead and strontium carbonates, however, induce the separation of aragonite at lower temperatures.
Form an insoluble calcium soap. The interaction between the soaps, the phosphates and the carbonates which are brought by the blood and lymph to the part results in the weaker fatty acids being replaced by phosphoric and carbonic acid, and thus in the formation of highly insoluble calcium phosphate and carbonate deposits in the disorganized tissues.
On fusion with alkaline carbonates and hydroxides it undergoes oxidation to silica which dissolves on the excess of alkali yielding an alkaline silicate.
(1) The metallic carbonates are the salts of carbonic acid, H 2 CO 3.
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.
Most metals form carbonates (aluminium and chromium are exceptions), the alkali metals yielding both acid and normal carbonates of the types Mhco 3 and M 2 CO 3 (M = one atom of a monovalent metal); whilst bismuth, copper and magnesium appear only to form basic carbonates.
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.
Most other carbonates are formed by precipitation of salts of the metals by means of alkaline carbonates.
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 alkaline carbonates undergo only a very slight decomposition, even at a very bright red heat.
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.
The individual carbonates are described under the various metals.
(2) The organic carbonates are the esters of carbonic acid, H 2 CO 3, and of the unknown ortho-carbonic acid, C(OH) 4.
The sulphur exists in the soil chiefly in the form of sulphates of magnesium, calcium and other metals; the phosphorus mainly as phosphates of calcium, magnesium and iron; the potash, soda and other bases as silicates and nitrates; calcium and magnesium carbonates are also common constituents of many soils.
In the ordinary chemical analyses of the soil determinations are made of the nitrogen and various carbonates present as well as of the amount of phosphoric acid, potash, soda, magnesia and other components soluble in strong hydrochloric acid.
The presence of a base such as lime or magnesia (or their carbonates) is also essential, as well as an adequate degree of moisture: in dry soils nitrification ceases.
Second in importance is the carbonate, calamine (q.v.) or zinc spar, which at one time was the principal ore; it almost invariably contains the carbonates of cadmium, iron, manganese, magnesium and calcium, and may be contaminated with clay, oxides of iron, galena and calcite; "white calamine" owes its colour to much clay; "red calamine" to admixed iron and manganese oxides.
Neither mechanical nor magnetic concentration can effect much in the way of separation when, as in many complex ores, carbonates of iron, calcium and magnesium replace the isomorphous zinc carbonate, when some iron sulphide containing less sulphur than pyrites replaces zinc sulphide, and when gold and silver are contained in the zinc ore itself.
Zinc carbonate, ZnCO 3, occurs in nature as the mineral calamine (q.v.), but has never been prepared artificially, basic carbonates, ZnCO 3 .xZn(OH) 2, where x is variable, being obtained by precipitating a solution of the sulphate or chloride with sodium carbonate.
When boiled with alkaline carbonates it is converted into strontium carbonate.
In the Red Sea the " Pola " expedition discovered a calcareous .00ze similar to that of the Mediterranean, and the formation of a stony crust by precipitation of calcium and magnesium carbonates may be recognized as giving origin to a recent dolomite.
Thus the sulphate constitutes the minerals anhydrite, alabaster, gypsum, and selenite; the carbonate occurs dissolved in most natural waters and as the minerals chalk, marble, calcite, aragonite; also in the double carbonates such as dolomite, bromlite, barytocalcite; the fluoride as fluorspar; the fluophosphate constitutes the mineral apatite; while all the more important mineral silicates contain a proportion of this element.
The aqueous solutions of all the carbonates when boiled undergo decomposition with liberation of ammonia and of carbon dioxide.
It is incompatible with carbonates of the alkalis.
Sodium carbonates are also widely dispersed in nature, forming constituents of many mineral waters, and occurring as principal saline components in natron or trona lakes, as efflorescences in Lower Egypt, Persia and China, and as urao in Mexico, Colombia and Venezuela.
In Wyoming, California and Nevada enormous deposits of carbonates, mixed in some cases with sulphate and with chloride, occur.
It also enters (as carbonates) into the composition of many minerals, such as chalk, dolomite, calcite, witherite, calamine and spathic iron ore.
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 is a constituent of the minerals cerussite, malachite, azurite, spathic iron ore, calamine, strontianite, witherite, calcite aragonite, limestone, &c. It may be prepared by burning carbon in excess of air or oxygen, by the direct decomposition of many carbonates by heat, and by the decomposition of carbonates with mineral acids, M2C03+2HC1=2MCl-FH 2 O+CO 2.
The gas is rapidly absorbed by solutions of the caustic alkalis, with the production of alkaline carbonates (q.v.), and it combines readily with potassium hydride to form potassium formate.
It reacts with alcohol to form chlorcarbonic ester and ultimately diethyl carbonate (see Carbonates), and with ammonia it yields urea.
It Is Easily Soluble In Solutions Of The Caustic Alkalis, Provided They Are Not Too Concentrated, Forming Solutions Of Alkaline Carbonates And Sulphides, Cos 4Kho = K2C03 K 2 S 2H20.