Basic lead carbonate

“ The hardening is based on the reaction of the lead oxide with glycerine (Moraffsky) .
[50] It is very instructive to observe that lead not only easily forms basic salts, but also salts containing several acid groups. Thus, for example, lead carbonate occurs in nature and forms compounds with lead chloride and sulphate. The first compound, known as corneous lead, phosgenite, has the composition PbCO3,PbCl2; it occurs in nature in bright cubical crystals, and is prepared artificially by simply boiling lead chloride with lead carbonate. ”

“ According to its chemical composition, white lead is a compound of lead carbonate and lead hydroxide, that is, a basic lead carbonate. [Pg 76] Commercial white lead, apart from intentional admixtures of other white substances, contains lead carbonate and lead hydroxide in varying proportions, as is shown by the following analyses by Mulder, who found that all the samples examined by him were composed according to one or other of the following formulæ:—
According to Hochstetter, the manufacture of white lead must be directed to obtaining the compound 2 PbCO3. ”

“ After cooling thoroughly, the cold basic acetate, which may now have crystallised or separated out more or less, according to the strength of the solution, is treated with carbonic acid gas, whereby the basic acetate, in the presence of the ammonia set free, is converted into basic carbonate of lead of exceptionally white colour, and with high basicity and covering power, proper care being taken as specially indicated later on. ”

“ White lead is prepared according to very different methods, the principle of which consists in subjecting a solution of tribasic lead acetate to the action of carbonic acid, by which the basic carbonate is produced and the neutral acetate formed, the latter being then reconverted into the basic acetate, which again serves to produce white lead and so on. ”

“ If the heat be too high, and the vapours too copious, the carbonic acid escapes in a great measure, and the metallic lead, less acted upon, affords a much smaller product.
When the process is well managed, as much carbonate of lead is obtained, as there was employed of metal; or, for 300 pounds of lead, 300 of ceruse are procured, besides a certain quantity of metal after the crusts are removed, which is returned to the melting-pot. The mixture introduced into the boxes serves only once; and if carbonate of potash has been used, the residuary matter is sold to the hatters. ”

“ Here the various ways in which it is apt to be insidiously introduced into the body, chiefly by the action of chemical agents on metallic lead itself, will come under consideration.
Of the Action of Air and Pure Water on Lead. When lead is exposed to the air it becomes tarnished. This 400arises from a thin crust of carbonate of lead being formed; for the crust dissolves with brisk effervescence in acetic acid. The formation of carbonate is accelerated by moisture and probably by the presence of an unusual proportion of carbonic acid in the air. ”

“ The solution of acetate of ammonia may be recovered from [232] the white lead, and be repeatedly used, for the conversion of further quantities of oxide of lead into hydrate and acetate of lead, which hydrate and acetate are converted into carbonate of lead by the injection of carbonic acid. Theoretically, a given weight of acetate of ammonia in solution, used in conjunction with carbonic acid, should be capable of converting an unlimited quantity of oxide of lead into carbonate of lead ”

“ While these changes are going on, a small quantity of lead will be dissolved, as may be shown by carefully filtering the water acidulating with a drop or two of nitric acid, and evaporating to dryness. Sulphuretted hydrogen is also a good test, occasioning, where lead is present, first a brown color, and subsequently a black precipitate. Christison has proved that the lead which is dissolved, is in the form of the carbonate, and hydrate of the oxide, or, oxide of lead, carbonic acid and water. ”

“ When pure carbonate is wanted, that dry mass must be mixed with its own bulk of ground coal, sawdust, or charcoal, and thrown into a reverberatory furnace, like fig. 1038., but with the sole all upon one level. Here it must be exposed to a heat not exceeding 650° or 700° F.; that is, a little above the melting heat of lead; the only object being to volatilize the sulphur present in the mass, and carbonate the alkali. Now, it has been found, that if the heat be raised to distinct redness, the sulphur will not go off, but will continue in intimate union with the soda. ”

“ Now, this striking through is owing to a slight process of saponification, no doubt owing to an interchange between the carbonic acid of the lead carbonate and the stearic and oleic acids of the oil with which the lead is mixed; so that, in time, the white lead, which has a body which makes it so great a favourite with artists, loses that body, and becomes a transparent or semi-transparent substance, something like lead plaster. Here is a reason why white lead should not be used unless the ground has previously been brought to a light colour. ”

“ In white-lead manufactories a very important and simple improvement has been effected of late in some places by abandoning the practice of dry-grinding. In all manufactories of the kind, the ultimate pulverizing of the white lead has been long performed under water. But in general the preparatory process of rolling, by which the carbonate is separated from the sheets of lead on which it is formed, continues to be executed dry. This is a very dangerous operation, because the workmen must inhale a great deal of the fine dust of the carbonate. ”

“ Like aluminium carbide it is slowly decomposed by water with the production of methane. 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. ”

“ 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. White lead is an earthy, amorphous powder. ”

“ An approximate method is based upon the reduction of lead oxide by the carbon and hydrogen of the coal, the amount of lead reduced affording a measure of the oxygen expended, whence the heating power may be calculated, 1 part of pure carbon being capable of producing 341⁄2 times its weight of lead. ”

“ The formation of carbonate takes place with considerable rapidity. In twelve ounces of distilled water, contained in a shallow glass basin loosely covered to exclude the dust, twelve brightly polished lead rods weighing 340 grains, will lose two grains and a half in eight days; and the lead will then show evident marks of corrosion. The process of corrosion goes on so long as atmospheric air is allowed to play freely on the surface of the water. In twenty months I have obtained 120 grains from an ounce of lead rods kept in 24 ounces of distilled water. ”

“ Several combinations of copper with carbonic acid are known, while lead is readily converted into lead carbonate by oxidation. The part played by the carbon compounds resulting from the decomposition of animal and vegetable substances has hitherto received little attention, but this decomposition of organic material is probably the chief cause of the beautiful blue patina. [32] The action of oxygen will depend upon the composition of the metal, upon the locality, and upon numerous other circumstances, while the colour of the patina will vary accordingly. ”

“ The heat is then raised in (relative) absence of air, when the two elements named unite into sulphur-dioxide, while a regulus of molten lead remains. Lead ores are smelted in the reverberatory furnace, the ore-hearth, and the blast-furnace. The use of the first two is restricted, as they are suited only for galena ores or mixtures of galena and carbonate, which contain not less than 58% lead and not more than 4% silica; further, ores to be treated in the ore-hearth should run low in or be free from silver, as the loss in the fumes is excessive. ”

“ Concentration of the fine Metal in Lead.—The best flux for quartz, which makes up the earthy matter of most gold ores, is soda, and this is best added as carbonate or bicarbonate. By theory, [20] 50 grams of quartz will require 88.5 grams of the carbonate, or 140 grams of the bicarbonate, to form sodium silicate, which is a glassy, easily-fusible substance, making a good slag. If the bicarbonate is used, and heat is applied gradually, steam and carbonic acid are given off at a comparatively low temperature, and the carbonate is left ”

“ Of a cool neutral tint, it has, in common with all carbonaceous blacks, a preserving influence on white when duly mixed therewith; which it owes, chemically, to the bleaching power of carbon, and, chromatically, to the neutralizing and contrasting power of black with white. Compounded slightly with blue black, and washed over with zinc white, white lead may be exposed to any ordinary impure atmosphere with comparative impunity. It would be well for art if carbon had a like power upon the colour of oils, but of this it is deficient ”

“ There is another excellent test for the purity of white lead, which is this. If you take a small portion, and grind it up with a little carbonate of soda into a small pellet about the size of a pea, and then put it upon a piece of charcoal and hold it in the middle flame of a blow-pipe for some short time, the sulphate of baryta becomes decomposed, and you get sulphide of sodium formed. If this sulphide of sodium be acted upon by an acid liquid, sulphuretted hydrogen is given off, which could not be formed from carbonate of lead, for in it there is no sulphur at all ”

“ Free carbonic acid is evolved during the fermentation or decay of vegetable matter, and hence the absolute necessity of preventing the leaves of trees falling into water-cisterns formed of lead. The ‘eau de rose’ and the ‘eau d’orange’ of commerce, which are pure distilled water holding in solution small quantities of essential oil, and are imported in leaden canisters, always contain a small quantity of lead, and deposit a sediment, which is not the case when they are kept in glass or incorrodible vessels. ”

“ Hybrid Fuel Cells (MCFC/SOFC)
Another kind of hybrid fuel cells presenting a growing interest is constituted by an electrolyte combining solid oxides with molten carbonates (Benamira et al., 2011, 2012) . Oxide ions are mostly responsible for the conductivity in the oxide phase and carbonates in the carbonate phase. ”

“ Most of the earthy carbonates are found abundantly in nature. In general the salts of this class may be formed by adding an alkaline carbonate to a salt of the metal in solution by double decomposition.
Prop. The carbonates of the alkalies are soluble in water; those of the other bases are for the most part insoluble, except the water is highly charged with carbonic acid. From most of them carbonic anhydride or anhydrous carbonic acid can be easily expelled by heat. ”

“ When heated, lead melts, and in the open air is either totally or partially transformed into white lead sulphate, PbSO4, as it also is by many oxidising agents (hydrogen peroxide, potassium nitrate) . Lead sulphate is also insoluble in water, [43] and lead is but rarely met with in this form in nature. The chromates, vanadates, phosphates, and similar salts of lead are also somewhat rare. The carbonate, PbCO2, is sometimes found in large masses, especially in the Altai region. Lead sulphide is often worked for extracting the silver which it contains ”

“ Carbonic acid occurs in nature, combined with many salifiable bases; as in the carbonates of soda, baryta, strontia, magnesia; the oxides of iron, manganese, zinc, copper, lead, &c. From these substances it may be separated, generally speaking, by strong ignition, or, more readily, by the superior affinity of muriatic, sulphuric, or nitric acid, for the earth or metallic oxide. It is formed whenever vegetable or animal substances are burned with free access of air, from the union of their carbonaceous principle with atmospheric oxygen. ”

“ The imperishable nature of carbon, in its various forms of lamp-black, ivory-black, wood-charcoal, and graphite or black lead, holds out much greater promise of being usefully employed in the manufacture of a permanent writing material; since, for this substance, in its elementary condition and at ordinary temperatures, there exists no solvent nor chemical reagent capable of affecting its alteration. ”

“ Most metals form carbonates (aluminium and chromium are exceptions) , the alkali metals yielding both acid and normal carbonates of the types MHCO3 and M2CO3 (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 + CO2 = MHCO3, and from these acid salts the normal salts may be obtained by gentle heating, carbon dioxide and water being produced at the same time, 2MHCO3 = M2CO3 + HO2 + CO2. ”