2

of sulphuric acid (H, SO). 1 part dissolves in 6895 parts of water at 14° C., and in 9638 parts of boiling water.

The Carbonate is produced by the action of the neutral carbonates of potassium or ammonium (K,CO, or [NH, CO) on solutions of strontium salts: it is a white precipitate.

Its formula is Sr, CO,.

2

This salt is more soluble in solutions of ammonium salts, especially chloride of ammonium, than is the corresponding barium compound. It dissolves in 18,045 parts of water at the ordinary temperature, but in a much less quantity of boiling water; it is readily decomposed by most acids; but in solutions of carbonic acid gas (CO) it dissolves without decomposition, in the same manner as the carbonate of barium, forming the analogous compound, namely, the acid carbonate of strontium (SrHCO).

The Oxalate is produced by the action of oxalic acid (H,C2O1), or of soluble oxalates, even in dilute solutions of strontium salts. It is a white precipitate.

Its formula is Sr,C,O,.

This salt is very soluble in hot aqueous solutions of chloride or nitrate of ammonium; it is very sparingly soluble in cold water, but dissolves in 19.2 parts of boiling water; it is dissolved readily by most strong acids, but not by acetic acid (HC,H,O,, or HÃ). THE FERROCYANIDE is soluble.

THE PHOSPHATE is produced by the action of phosphate of sodium (Na,HPO1) on solutions of strontium salts. Its formula is Sr,HPO. It dissolves readily in most ammonium salts, but is reprecipitated by the addition of hydrate of ammonium (NH,HO). It is insoluble in water, but dissolves in most acids.

THE SILICOFLUORIDE is soluble, especially in the presence of acids.

The special tests of the first subdivision are without welldefined action on salts of strontium.

The special tests for strontium which the student should particularly remember are these:-the blowpipe flame, the action of sulphates on soluble strontium salts, and the absence of the reaction with chromates and silicofluorides; by means of this last

test this metal is usually distinguished from barium, the reactions of which in most other respects are so similar to its own.

SALTS OF CALCIUM.

Solution for the reactions :-chloride of calcium (CaCl) in water.

Calcium, like the two preceding metals, forms two combinations with oxygen, a protoxide (Ca,O), and a peroxide (Ca,O,): it combines with almost every acid-radical to produce salts; which, like those of barium and strontium, are all proto-salts. They are colourless, except in cases where the acid-radical introduces colour. They are devoid of poisonous properties.

These salts resemble those of the two preceding metals in their behaviour when heated before the blowpipe on charcoal, being for the most part decomposed into the oxide (lime). This oxide remains infusible, and is remarkably incandescent, the light which it emits increasing with the intensity of the heat, and reaching its maximum only when the lime is subjected to the highest temperature at our disposal-such, for instance, as that produced by the oxyhydrogen blowpipe. The light thus obtained has been utilized, and is known as the "lime light." The chloride, bromide, and iodide of calcium resemble the corresponding salts of barium and strontium in remaining undecomposed before the blowpipe flame on charcoal. A platinum wire, moistened with a solution of a calcium salt, tinges the flame of an orange-red colour; the colour, however, imparted by a pure salt of calcium is a very pure red, the orange tint which it generally has being in fact owing to the presence of a trace of sodium; the red of pure calcium salts may even be mistaken for the crimson of strontium compounds; actual comparison, nevertheless, shows the difference. The red colour may be observed even with the insoluble salts of calcium, by heating them before the blowpipe after they have been moistened with a strong acid, such as hydrochloric acid. The borax-bead is colourless.

The principal insoluble salts of calcium are the hydrate, the sulphate, the carbonate, the ferrocyanide, and the phosphate.

THE CHROMATE is soluble.

THE HYDRATE is produced by the action of hydrate of potassium (KHO) on solutions of calcium salts; the hydrate of ammonium (NH,HO) produces no precipitate. The hydrate is a white bulky precipitate.

Its formula is CaHO.

This salt dissolves in about 730 parts of water at the ordinary temperature, but at temperatures about the boiling-point, in from 1310 to 1350 parts, thus presenting the peculiarity of being less soluble in hot than in cold water. It dissolves readily in most acids.

THE SULPHATE is produced by the action of sulphuric acid (H2SO) or soluble sulphates on solutions of calcium salts, unless they are very dilute. It is a white, somewhat crystalline precipitate.

Its formula is Ca, SO,+2aq.

The solubility of this salt in water is increased by the presence of chloride of ammonium, or of other ammonium salts, and also by sodium salts, especially the chloride of sodium; from its solution in water containing this latter compound it is not reprecipitated, as the sulphate of strontium is, by the addition of sulphuric acid (H2SO). Sulphate of calcium is far more soluble in water than the corresponding salts of barium and strontium, 1 part requiring about 460 parts of water, either at the ordinary temperature or that of boiling water, for its solution.

3

The Carbonate is produced by the action of the neutral carbonate of potassium or ammonium (K,CO, or [NH,],CO1) on solutions of calcium salts. It is a bulky white precipitate, but when seen under the microscope, is found (as is the case with many other precipitates) to be crystalline. It is a substance which is said to be dimorphous, for it is capable of assuming two distinct crystalline forms not belonging to the same system: the occurrence of these forms is determined by the temperature at which the salt is produced; if precipitated in the cold, the crystals assume forms belonging to the rhombohedral system; if at the temperature of boiling water, they belong to the right prismatic system.

Its formula is Ca,CO,.

When recently precipitated, it dissolves with comparative ease in concentrated solutions of chloride of ammonium and other ammonium salts; it is also soluble to a slight extent in solutions of chloride of sodium. In water it is very slightly soluble, 1 part requiring 10,600 parts at the ordinary temperature, and 8834 parts of water at 100° C. for its solution. It is decomposed by most acids, and dissolved by solution of carbonic acid gas (CO2), with formation of the acid carbonate (CaHCO3).

The Oxalate is produced by the action of oxalic acid (H,C2O1), or soluble neutral oxalates, on solutions of calcium salts; when extremely dilute, appearing after the lapse of a few seconds. It is a granular precipitate.

The formula of the salt dried at 100° C. is Ca,C,O1+aq.

It is insoluble in chloride of ammonium and in water; it is also insoluble in acetic acid (HA), but dissolves in the stronger acids, nitric and hydrochloric, readily.

The Ferrocyanide is produced by the action of ferrocyanide of potassium (K,Cfy) on solutions of calcium salts, especially on standing, and more quickly still by boiling. It is a dense white precipitate. Its composition is that of a ferrocyanide of potassium and calcium; it is KCaCfy+1aq. This salt is more insoluble in the presence of chloride of ammonium and other salts; it dissolves in 795 parts of water at 15° C., and in 145 parts of boiling water: it is soluble in dilute, but insoluble in concentrated hydrochloric acid.

THE PHOSPHATE is produced by the action of the phosphate of sodium (Na, HPO1) on solutions of calcium salts. It is a bulky white precipitate. Its composition is probably Ca, HPO1. It is somewhat soluble in solutions of ammonium salts, and also in solutions of chloride of sodium.

THE SILICOFLUORIDE is soluble.

The special tests of the preceding subdivision are without welldefined action on the salts of calcium.

The special means of distinguishing calcium from strontium and barium which the student should remember are these:-the

blowpipe flame and remarkable incandescence; the comparative insolubility of the ferrocyanide, and the comparative solubility of the sulphate, as serving to distinguish calcium from both strontium and barium; and the solubility of the chromate and silicofluoride as distinguishing it from barium.

SECTION II.-Precipitated by Carbonate of ammonium ([NH1],CO1), and redissolved by Chloride of ammonium (NHCl).

SALTS OF MAGNESIUM.

SALTS OF MAGNESIUM.

This metal resembles the three preceding in forming one class of salts only, namely, proto-salts. These salts, although resembling those of barium, strontium, and calcium in many respects, yet differ from them in many chemical characters. They are white, unless when combined with a coloured acid-radical, and act powerfully as purgatives when taken into the animal system.

When heated on charcoal they are for the most part decomposed, and the oxide formed is as infusible and highly incandescent as lime: the chloride, bromide, iodide, &c., if perfectly free from water, are not decomposed; but if water be present, they too decompose by fusion thus

2MgCl+H2O=Mg20+2HC1: this decomposition will be found to obtain among many of the succeeding metals. Magnesium salts impart no colour to the blowpipe flame; but when strongly heated in the oxidizing flame, after having been moistened with solution of nitrate of cobalt (CONO,), the mass is found on cooling to have acquired a very pale pink colour. The borax-bead is transparent and colourless.

The principal insoluble salts by means of which this metal is recognized are the hydrate, the carbonate, the ferrocyanide and the phosphate.

THE CHROMATE is soluble.

The Hydrate is produced by the action of the hydrate of potassium (KHO). It is a bulky white precipitate. The hydrate of ammonium (NH, HO) exerts a very peculiar action upon solu