monate of potassa also gives decisive results when no other bases besides soda or potassa are present, and especially if these latter are present as chlorides or nitrates. Even from very dilute solutions of salts of soda, antimonate of potassa added in excess will, after twelve hours' standing, throw down antimonate of soda, the crystals of which may always be readily and distinctly recognised under the microscope by their form-quadrilateral octahedrons.

§ 92.

SUPPLEMENT TO THE FIRST GROUP.

LITHIA (LI O).

Lithia dissolves with difficulty in water; it does not attract moisture from the air. Most of its salts are soluble in water; some of them are deliquescent (chloride of lithium). Carbonate of lithia is difficultly soluble, particularly in cold water. Phosphate of soda produces, in not over dilute solutions of salts of lithia, upon boiling, a heavy white crystalline precipitate of basic phosphate of lithia (3 Li O, PO, + aq.). From very dilute solutions of lithia the same basic phosphate is obtained by adding phosphate of soda and one or two drops of solution of soda to the solution, evaporating the mixed fluid to dryness, and treating the residue with water. The basic phosphate of lithia obtained is sparingly soluble in water, and still less so in ammoniated water; it dissolves much more readily in water containing salts of ammonium. It is immediately dissolved by acids; addition of ammonia produces no precipitate in somewhat dilute acid solutions in the cold, but upon boiling, a precipitate separates. The basic phosphate of lithia fuses before the blowpipe, and gives upon fusion with carbonate of soda on the platinum wire a clear bead; when fused upon charcoal, it is absorbed by the pores of the latter body (another difference between it and the phosphate of the alkaline earths). Tartaric acid and bichloride of platinum fail to precipitate even concentrated solutions of salts of lithia; but in a solution of chloride of potassium containing chloride of lithium, bichloride of platinum readily produces a precipitate containing lithia (Jenzsch). If a salt of lithia (more particularly chloride of lithium) is exposed on a platinum wire to the inner blowpipe flame, the outer flame shows a strong CARMINE tint. Presence of salts of soda (but not of salts of potassa) conceals this reaction. Addition of chloride of silver promotes it in the case of some, but not of all salts of lithia. If spirit of wine is poured over a salt of lithia (more particularly chloride of lithium), and then kindled, the flame appears of a CARMINE colour; presence of salts of soda conceals this reaction.

To detect lithia in presence of potassa and soda, convert the bases into dry chlorides; treat them, after addition of a drop of hydrochloric acid, with a mixture of absolute alcohol and anhydrous ether; filter, distil, and treat the residue remaining after distillation again with the said mixture, after previous addition of a drop of hydrochloric acid; filter, concentrate the filtrate by evaporation, and then set fire to the concentrated fluid. A carmine-coloured flame indicates the presence of lithia. The residue remaining after evaporation of the alcohol must dissolve in water to a clear fluid; the solution must not be precipitated by carbonate of ammonia (lime, strontia), and must give the above-mentioned reaction with phosphate of soda. This method is based upon the insolubility of chloride

of potassium, and chloride of sodium in absolute alcohol and ether, in which chloride of lithium readily dissolves.

§ 93.

SECOND GROUP.

BARYTA, STRONTIA, LIME, MAGNESIA.

Properties of the group.-The alkaline earths are soluble in water in the pure (caustic) state and as sulphides. Magnesia, however, dissolves but very sparingly in water. The solutions manifest alkaline reaction; the alkaline reaction of magnesia is most clearly apparent when that earth is laid upon moistened test-paper. The neutral carbonates and phosphates of the alkaline earths are insoluble in water. The solutions of the salts of the alkaline earths are therefore precipitated by alkaline carbonates and phosphates, whilst hydrosulphuric acid fails to precipitate them under any condition. This deportment distinguishes the oxides of the second group from those of the first. The alkaline earths and their salts are non-volatile and colorless; their solutions are not precipitated by sulphide of ammonium, nor by carbonate of baryta.

Special Reactions.
$94.

a. BARYTA (Ba O).

1. Caustic baryta is pretty readily soluble in hot water, but rather difficultly so in cold water; it dissolves easily in dilute hydrochloric or nitric acid. Hydrate of baryta does not lose its water upon ignition.

2. Most of the salts of baryta are insoluble in water. The soluble salts do not affect vegetable colors, and are decomposed upon ignition, with the exception of chloride of barium. The insoluble salts dissolve in dilute hydrochloric acid, except the sulphate of baryta. Nitrate of baryta and chloride of barium are insoluble in alcohol, and do not deliquesce in the air. Concentrated solutions of baryta are precipitated by hydrochloric or nitric acid added in large proportions, as chloride of barium and nitrate of baryta are not soluble in the aqueous solutions of the said acids.

3. Ammonia (free from carbonic acid) produces no precipitate in the aqueous solutions of salts of baryta; potassa or soda (free from carbonic acid) only in highly concentrated solutions. Water redissolves the bulky precipitate of CRYSTALS OF BARYTA (Ba O, HO + 8 aq.) produced by potassa or soda.

4. Alkaline carbonates throw down from solutions of baryta CARBONATE OF BARYTA (Ba O, C O2) in the form of a white precipitate. When carbonate of ammonia is used as the precipitant, or if the solution was previously acid, complete precipitation takes place only upon heating the fluid. In chloride of ammonium the precipitate is soluble to a trifling yet clearly perceptible extent; in very dilute solutions of baryta, therefore, which contain much chloride of ammonium, carbonate of ammonia produces no precipitate.

5. Sulphuric acid and all the soluble sulphates, also solution of sulphate of lime, produce even in very dilute solutions of baryta, a

heavy, finely pulverulent, white precipitate of SULPHATE OF BARYTA (Ba O, S O), which is insoluble or very difficultly soluble in dilute acids, alkalies, and salts of ammonia. As a rule, this precipitate is formed immediately upon the addition of the reagent; from highly dilute solutions, however, especially when strongly acid, it separates only after some time. Sulphate of baryta is completely decomposed by fusion with carbonates of the alkalies-less readily and less completely by boiling with solution of carbonate of soda and carbonate of potassa. The decomposition leads to the formation of sulphates of the alkalies, which are soluble in water, and carbonate of baryta, which is insoluble in that fluid. Digestion with solution of carbonate of ammonia in the cold fails to effect the decomposition of sulphate of baryta, as also boiling with a solution of 1 part of carbonate and 3 parts of sulphate of potassa (H. Rose).

6. Hydrofluosilicic acid throws down from solutions of baryta SILICOFLUORIDE OF BARIUM (Ba Fl + Si Fl), in form of a colorless, crystalline, quickly subsiding precipitate. In dilute solutions this precipitate is formed only after the lapse of some time; it is perceptibly soluble in hydrochloric and nitric acids. Addition of an equal volume of alcohol hastens the precipitation and makes it so complete that the filtrate remains clear upon addition of sulphuric acid.

7. Phosphate of soda produces in neutral or alkaline solutions of baryta a white precipitate of PHOSPHATE OF BARYTA (2 Ba O, H 0, P 0), which is soluble in free acids. Addition of ammonia only slightly increases the quantity of this precipitate; chloride of ammonium dissolves it to a clearly perceptible extent.

8. Oxalate of ammonia produces in moderately dilute solutions of baryta a white, pulverulent precipitate of OXALATE OF BARYTA (Ba O, O + aq.), which is soluble in hydrochloric and nitric acids. When recently thrown down, this precipitate dissolves also in oxalic and acetic acids; but the solutions speedily deposit binoxalate of baryta (Ba 0,0 + H0,0 + 2 aq.) in the form of a crystalline powder.

9. Salts of baryta in powder, when heated with dilute spirit of wine, impart to the flame a YELLOWISH colour, which, however, is not very characteristic.

10. Salts of baryta, particularly chloride of barium, when exposed on a platinum wire to the inner blowpipe flame, color the outer flame YELLOWISH-GREEN. With chloride of barium and nitrate and acetate of baryta this reaction is the most distinct, but it is also shown by carbonate and sulphate of baryta. The presence of salts of lime and strontia does not prevent the reaction; addition of chloride of silver considerably heightens its intensity.

§ 95.

b. STRONTIA (Sr O).

1. Strontia and its hydrate and salts manifest nearly the same general deportment and properties as baryta and its corresponding compounds.Hydrate of strontia is more difficulty soluble in water than hydrate of baryta.—Chloride of strontium dissolves in absolute alcohol, and deliquesces in moist air. Nitrate of strontia is insoluble in absolute alcohol, and does not deliquesce in the air.

2. The salts of strontia manifest with ammonia and potassa, and also

with the alkaline carbonates and with phosphate of soda, nearly the same deportment as the salts of baryta. Carbonate of strontia dissolves somewhat more difficultly in chloride of ammonium than is the case with carbonate of baryta.

3. Sulphuric acid and sulphates precipitate from solutions of strontia SULPHATE OF STRONTIA (Sr O, SO), in form of a white powder, which is insoluble in dilute acids and alkalies. Application of heat greatly promotes the precipitation. Sulphate of strontia is far more soluble in water than sulphate of baryta ; owing to this readier solubility, the precipitated sulphate of strontia separates from rather dilute solutions in general only after the lapse of some time; and this is invariably the case (even in concentrated solutions) if solution of sulphate of lime is used as precipitant. In boiling hydrochloric acid sulphate of strontia dissolves perceptibly, a solution of the kind showing, after dilution with water, a distinct turbidity upon the addition of a drop of solution of chloride of barium. Sulphate of strontia is readily and completely decomposed by fusion with carbonates of the alkalies, and by boiling with their solutions ; it is decomposed also when long digested in the cold with solution of carbonate of ammonia, or boiled with a solution of 1 part of carbonate of potassa and 3 parts of sulphate of potassa (difference from sulphate of baryta).

4. Hydrofluosilicic acid fails to produce a precipitate even in concentrated solutions of strontia; even upon addition of an equal volume of alcohol no precipitation takes place, except in very highly concentrated solutions.

5. Oxalate of ammonia precipitates even from rather dilute solutions, OXALATE OF STRONTIA (2 S, O, O + 5 aq.), in form of a white powder, which dissolves readily in hydrochloric and nitric acid, and perceptibly in salts of ammonia, but is only sparingly soluble in oxalic and acetic acid.

6. If salts of strontia soluble in water or alcohol are heated with dilute spirit of wine, and then kindled, the flame appears of an intense CARMINE color, more particularly upon stirring the alcoholic mixture.

7. Chloride of strontium when exposed on platinum wire to the inner blowpipe flame, imparts an intense RED color to the outer flame. With carbonate and sulphate of strontia the coloration is less intense; addition of chloride of silver, however, makes the reaction with these two salts also lasting and distinct. Presence of baryta prevents this reaction of strontia.

$96.
C. LIME (Ca O).

1. Lime and its hydrate and salts present, in their general deportment and properties, a great similarity to baryta and strontia and their corresponding compounds. Hydrate of lime is far more difficultly soluble in water than the hydrates of baryta and strontia; it dissolves, besides, more sparingly in hot than in cold water. Hydrate of lime loses its water upon ignition. Chloride of calcium and nitrate of lime are soluble in absolute alcohol, and deliquesce in the air.

2. Ammonia, potassa, alkaline carbonates, and phosphate of soda, present nearly the same deportment with salts of lime as with salts of

baryta. Recently precipitated carbonate of lime (Ca O, C O2) is bulky and amorphous after a time, and immediately upon application of heat, it falls down and assumes a crystalline form. When recently precipitated, it dissolves pretty readily in solution of chloride of ammonium; but the solution speedily becomes turbid, and deposits the greater part of the dissolved salt in form of crystals.

3. Sulphuric acid and sulphate of soda produce immediately in very concentrated solutions of lime white precipitates of SULPHATE OF LIME (Ca O, SO,, HO+ aq.), which redissolve completely in a large proportion of water, and are still far more soluble in acids. In less concentrated solutions the precipitates are formed only after the lapse of some time; and no precipitation whatever takes place in dilute solutions. Solution of sulphate of lime of course cannot produce a precipitate in salts of lime; but even a cold saturated solution of sulphate of potassa, mixed with 3 parts of water, produces a precipitate only after standing from twelve to twenty-four hours. In solutions of lime which are so very dilute that sulphuric acid has no apparent action on them, a precipitate will immediately form upon addition of alcohol. When fused with carbonates of the alkalies, or boiled or digested with their solutions, sulphate of lime comports itself the same as sulphate of strontia. 4. Hydrofluosilicic acid does not precipitate salts of lime.

3

5. Oxalate of ammonia produces even in very dilute solutions of lime a white pulverulent precipitate of OXALATE OF LIME. The composition of this precipitate, when thrown down hot or from concentrated solutions, is Ca O, C, O, + aq.; whilst when thrown down cold from dilute solutions, it consists of a mixture of Ca O, C, O, + aq. with Ca O, C2 0, +3 aq. In very dilute solutions the precipitate forms only after some time. It is readily soluble in hydrochloric and nitric acids, but dissolves to a trifling extent only in acetic and oxalic acids.

2

2

6. Soluble salts of lime, when heated with dilute spirit of wine, impart to the flame of the latter a YELLOWISH-RED color, which is often confounded with that communicated to the flame of alcohol by salts of strontia.

7. Chloride of calcium, when exposed on a platinum wire to the inner blowpipe flame, imparts a RED colour to the outer flame. With the other salts of lime this reaction is less intense; with phosphate and borate of lime it fails altogether. Chloride of silver, as a rule, heightens the intensity of the color. Presence of baryta prevents this reaction of lime.

§ 97.

d. MAGNESIA (Mg O).

1. Magnesia and its hydrate are white powders of far greater bulk than the other alkaline earths and their hydrates. Magnesia and hydrate of magnesia are nearly insoluble both in cold and hot water. Hydrate of magnesia loses its water upon ignition.

2. Some of the salts of magnesia are soluble in water, others are insoluble in that fluid. The soluble salts of magnesia have a nauseous bitter taste; in the neutral state they do not alter vegetable colors; with the exception of sulphate of magnesia, they undergo decomposition when ignited, and the greater part of them even upon simple evaporation of their solutions. Nearly all the salts of magnesia which are insoluble in water dissolve in hydrochloric acid.