(2) By subliming an intimate mixture of dry mercuric sulphate, mercury, and salt :

HgSO.+Hg+2NaCl = Hg2Cl2+ Na2SO.

Give its properties.

It is a heavy, white, insoluble, tasteless powder. It vaporizes below redness, condensing to a yellow-white crystalline mass, soluble in boiling hot nitric acid. It is apt to contain some corrosive sublimate, a dangerous contamination when calomel is used for medicinal purposes. Recent experiments tend to show that the true formula is HgCl. It is much used medicinally.

How is mercuric iodide obtained?

HgI,, mercuric iodide, is prepared from a solution of mercuric chloride and potassium iodide. Yellow at first, it then becomes a scarlet dimorphous precipitate. It is employed medicinally.

How is mercurous iodide prepared?

Hg,I2, mercurous iodide, is formed from mercurous nitrate and potassium iodide. A greenish-yellow precipitate results from their union. Medicinally it is useful.

State the methods of preparing the oxides of mercury.

HgO, mercuric oxide; red oxide of mercury; red precipitate:(1) Oxidizing mercury at high temperature;

(2) Decomposing the nitrate by heat;

mate.

Excess of caustic potash added to a solution of corrosive subli

Properties: Red color; slightly soluble in water, giving alkaline reaction and metallic taste; highly poisonous; decomposed by heat into mercury and oxygen. A yellow or amorphous form is used with oleic acid for skin diseases.

Hg,O, mercurous oxide, suboxide or gray oxide of mercury:(1) Caustic potash added to mercurous nitrate;

(2) Digesting calomel with caustic potash. It is a grayish-black heavy powder insoluble in water and slowly decomposed by the action of light. The preparations known as blue-pill, gray ointment, mercury with chalk, etc., contain merely the finely divided metal.

How are the nitrates of mercury obtained?

Mercury and cold dilute nitric acid yield the mercurous nitrate, while hot concentrated nitric acid and mercury yield the mercuric nitrate.

What are the sulphates of mercury?

Mercuric sulphate, HgSO,, is derived from mercury and hot concentrated sulphuric acid, and used in some forms of galvanic batteries.

Mercurous sulphate, Hg2SO, is prepared from mercurous nitrate and sulphuric acid.

How is mercuric sulphide obtained?

HgS, mercuric sulphide, occurs as the mineral cinnabar, the principal source of mercury. It is also formed:

(1) By an excess of sulphuretted hydrogen passed through mercuric nitrate or chloride;

(2) By subliming a mixture of 6 parts of mercury and 1 part of sulphur.

State its properties and use.

(1) A black precipitate, changed by sublimation to a dark red and crystalline form.

(2) A red powder called vermilion. Its beauty of tint depends upon its fineness of division. Heated in air it decomposes to metallic mercury and sulphur dioxide. It is insoluble in caustic alkalies and mineral acids, excepting aqua regia. Its use is extensive as the pigment vermilion.

How is mercurous sulphide prepared?

HgS, mercurous sulphide, is prepared by passing sulphuretted hydrogen into a mercurous nitrate. The process forms a black precipitate decomposed by heat into mercuric sulphide and mercury.

What are the ammoniacal mercury compounds?

By the action of ammonia and its salts upon salts of mercury, a great variety of substances is formed. They may be regarded as salts of mercur-ammoniums, that is of ammonium molecules in which the hydrogen atoms are more or replaced by mercury according as the compound is formed from a mercurous or mercuric salt.

Give the tests for mercury compounds.

(1) All mercury salts are volatilized or decomposed at the temperature of ignition;

(2) Copper precipitates mercury from solutions;

(3) Stannous chloride forms a precipitate;

(4) Hydrogen sulphide and ammonium sulphide produce black precipitates, insoluble in ammonium sulphide;

(5) Potassium iodide yields a bright scarlet precipitate with mercuric salts, and a green precipitate with mercurous salts ;

(6) Charcoal and sodium carbonate yield metallic mercury.

What are some of the uses of mercury?

(1) Metallic mercury is used in the construction of barometers, thermometers, and other physical apparatus;

(2) To extract gold and silver from their ores by forming their amalgams;

(3) With tin it forms an amalgam for silvering glass-mirrors, and with silver and gold an amalgam for filling teeth.

VI. METALS OF THE YTTRIUM GROUP. State some of the facts regarding the yttrium group.

This group includes a considerable number of metals occurring in gadolinite, cerite, samarskite, and other rare minerals. The extraction and separation of the oxides of these metals are complex and difficult, and the number of distinct oxides or earths thus obtained is not exactly known. The existence of some of these metals is still a matter of dispute. The ten following may be considered established :—

These rare metals have only theoretical importance.

The existence

of scandium was predicted by Mendelejeff in advance of its actual discovery in nature. Cerium oxalate has a limited use in medicine.

VII. METALS OF THE ALUMINIUM GROUP.

What are the members of the aluminium group?
Aluminium, indium, gallium.

Give the characteristics of the aluminium group.

These metals are trivalent, forming compounds of the forms MC13, M2O3, etc.

Their oxides are weak bases and their sulphates unite with those of the alkali metals, forming double salts called "alums," which crystallize in regular forms of the isometric system.

ALUMINIUM.

Where is aluminium found?

Symbol Al.

Atomic weight 27.3.

Regarding its abundance in nature it may be ranked with sodium, calcium, and magnesium. As a silicate, it enters into the composition of all primitive rocks, of feldspars, slates, and clays; of the minerals garnet, emerald, topaz. As an oxide, Al,O,, it is the mineral corundum,

which in its various degrees of coloring and purity is the ruby, sapphire, Oriental topaz, Oriental amethyst, and Oriental emerald. An impure variety is called emery. As a phosphate, it occurs as turquoise. As a fluoride, it occurs as cryolite, ALF, 6NaF. As an aluminate, with iron, bauxite, a hydrated aluminate of iron. It is also a constituent of other less important minerals.

Give several methods of preparing aluminium.

(1) By decomposing aluminium chloride by metallic potassium (Wöhler's original method).

(2) By decomposing the double chloride of sodium and aluminium, AIF, 3NaF, by metallic sodium (Deville's process).

Both of these original processes have been supplanted by the modern electric methods :

(3) The electrolytic reduction of oxide of aluminium having a cover of fused cryolite, producing metallic aluminium (Heroult and Hall's processes); and

(4) The electrolytic reduction of corundum, Al,O,, with copper, producing an alloy of copper and aluminium (Cowle's process).

State the properties and uses of aluminium.

It is a tin-white metal, brilliant and capable of being highly polished; specific gravity 2.6 to 2.74; malleable and ductile; an excellent conductor of heat and electricity. It does not readily tarnish in air; is easily worked, and combines the properties of lightness and strength to an extraordinary degree. Its specific heat is very high, 0.2253, being double that of iron. Its melting-point is 625° C. It imparts great strength to its alloys. It is trivalent; forms only one class of compounds. As a metal it is used in the manufacture of delicate apparatus and ornamental objects. As an alloy with copper, called aluminium bronze, and with steel it is coming into constantly increasing usc.

What chemicals will produce aluminium chloride?
Aluminium chloride, AlCl,, is produced by:-

(1) Aluminium hydrate in hydrochloric acid (in solution); (2) Alumina, finely divided carbon, and chlorine gas:Al2O3+C3+Cl1 = 2AICI,+3CO

(an anhydrous solid).

What is the aluminium sodium salt?

AICI, NaCl, aluminium and sodium chloride, is a double salt obtained by melting together the proper proportions of the two chlorides.

How is aluminium fluoride prepared?

AlF, aluminium fluoride, is prepared by the action of gaseous silicon fluoride on alumina. Its cubic crystals, volatilizing at a red heat, are insoluble in water and resist the action of acids.

What is the aluminium sodium fluoride ?

AlF3,3NaF, aluminium and sodium fluoride, is found in nature as cryolite at Evigtok, Greenland.

How is it prepared and what is its use ?

It is prepared from hydrofluoric acid and a mixture of calcined alumina and sodium carbonate. Its natural crystals, softer than feldspar, are used in the preparation of aluminium; for the manufacture of sodaash; for aluminium sulphate, and in the production of glass resembling porcelain.

How does aluminium oxide occur?

Al2O3, aluminium oxide or alumina, occurs as the mineral corundum. It may be prepared from aluminium sulphate and an excess of ammonia hydrate. The bulky, white, gelatinous precipitate of aluminium hydrate thus obtained is converted into an oxide by ignition. The oxide is a white, tasteless, coherent mass, and little affected by acids, but fusible before the oxyhydrogen blowpipe. It acts as a weak base.

Give the hydrates of aluminium.

Monohydrate, Al,O,,H,O or AIO(OH);
Dihydrate ALO,2H,O or Al,O(OH);
Trihydrate Al2O3,3H2O or Al(OH)3.

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The monohydrate occurs native as diasphore dihydrate. The trihydrate occurs native as gibbsite. It has a powerful attraction for organic matter and precipitates solutions of vegetable coloring-matters forming pigments called lakes.' The fibre of cotton impregnated with alumina acquires the power of retaining coloring-matters, hence the great use of aluminous salts as mordants to produce fast colors.

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What are aluminates?

The hydrogen in aluminium trihydrate may be replaced by an equivalent quantity of various metals. Such compounds are called "aluminates, two of them occurring as minerals, spinel an aluminate of magnesium, Al,MgO, and gahnite an aluminate of zinc, Al1⁄2ZnO.

How is aluminium sulphide prepared?

AlS, aluminium sulphide, is obtained when vapor of carbon disulphide is passed over alumina at red heat. This sulphide is instantly decomposed by water with the evolution of sulphuretted hydrogen. How is aluminium sulphate produced?

Al2(SO4)3,18H2O, aluminium sulphate, is formed :

(1) From aluminium hydrate and dilute solution of sulphuric acid, then evaporating ;

(2) On a large scale by treating clay with sulphuric acid.