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should not be decomposed when colored, but may be reclaimed by dissolving in water, decolorizing with a small quantity of ammonia water, evaporating and granulating.

AMMONIUM AND SULPHUR.

Ammonium Monosulphide (NH4)2S.—When 2 volumes of ammonia gas and I volume of hydrogen sulphide are mixed at a temperature of —18°, ammonium monosulphide is formed. It forms colorless, glittering crystals, which commence to decompose at ordinary temperatures into ammonia and ammonic sulphydrate. This compound is prepared in aqueous solution by saturating 3 parts of solution of ammonia with hydrogen sulphide and then adding 2 parts of ammonia water. This is the official test-solution. It is a valuable reagent in the laboratory, and is very extensively used.

Ammonium Hydrosulphide, NH4SH.-This compound is obtained when ammonia gas and hydrogen sulphide are mixed at ordinary temperatures; on cooling to oo, colorless, acicular crystals separate. These crystals are formed when alcoholic ammonia is saturated with hydrogen sulphide. The compound is formed in aqueous solution when aqueous ammonia is saturated with hydrogen sulphide :

NH,OH + H,S = NHẠSH + H,O.

This solution and the preceding one of ammonium monosulphide are colored yellow on standing, owing to the formation of the higher ammonium polysulphides and water. There are at least three of these higher sulphides: ammonium tetrasulphide, (NH4)2S4, obtained by cooling the mother liquor from the pentasulphide and saturating it with ammonia and hydrogen sulphide; ammonium pentasulphide, (NH4)2S5, prepared by dissolving sulphur in the solution of hydrosulphide; and ammonium heptasulphide, (NH4)2S7, formed when the pentasulphide is exposed to the air.

OXYGEN SALTS OF AMMONIUM.

Ammonium Sulphate, (NH4)2SO4.—This salt is met with as a by-product in the manufacture of boric acid, and is found native as the mineral mascagnite. It is prepared by saturating ammoniacal gas-liquor with sulphuric acid, evaporating rapidly, and removing the crystals as they form by perforated ladles. As thus obtained the crystals are of a dark color. They are first allowed to drain well, then dissolved in water, treated with animal charcoal, filtered, and recrystallized.

Properties.-Ammonium sulphate occurs in large, transparent, rhombic crystals, isomorphous with potassium sulphate. They are soluble in 1.3 parts of water at 15°, and in 1 part of boiling water, insoluble in absolute alcohol, but slightly soluble in ordinary alcohol. On the application of heat the crystals melt

at 140°; at 280° they decompose, with evolution of ammonia, water, and nitrogen; at the same time ammonium sulphite with some sulphate sublimes.

Uses.-Ammonium sulphate is one of the most useful of the ammonium salts, since it forms the easiest method of recovering the ammonia from gas-liquors, and it is then used as a basis for the preparation of the other ammonium salts. It is especially employed in the manufacture of ammonia-alum and as a fertilizer.

Acid Ammonium Sulphate, NHHSO4, is obtained when the neutral sulphate is crystallized in dilute sulphuric acid.

It forms rhombic crystals which resemble in form those of acid potassium sulphate.

Ammonium Nitrate, NH4NO,.-The usual process for obtaining this salt is by saturating nitric acid with ammonium hydrate or carbonate; a somewhat more economical method consists in mixing solutions of ammonium sulphate and potassium nitrate; the result is double decomposition with the formation of potassium sulphate and ammonium nitrate; the latter, being much more soluble, is obtained after the potassium sulphate has crystallized

out.

Properties. Ammonium nitrate is found in commerce in long, thin, colorless, rhombic prisms, or in white, fused masses, or as a white, granular powder; it is odorless, has a sharp, bitter, saline taste, and is somewhat deliquescent. Its aqueous solution is neutral to litmus paper. The salt is soluble at 15° in 0.5 part of water and in 20 parts of alcohol; it is very soluble in boiling water and in 3 parts of boiling alcohol. It melts at 165°, and between 230° and 250° it is decomposed into nitrogen monoxide and water, as follows:

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A small proportion of the salt is sublimed unchanged at the same time. The fused salt acts as an energetic oxidizing agent. Uses. Ammonium nitrate is used largely in the production. of nitrogen monoxide, or laughing gas. The salt when dissolved in water produces a decided fall in temperature.

Ammonium Nitrite, NH4NO, is formed by decomposing a solution of silver nitrite with ammonium chloride:

NH4Cl AgNO2

=

NH4NO2+ AgCl.

The crystals are obtained from this by evaporating the filtrate at ordinary

temperatures over sulphuric acid. Ammonium nitrite occurs in indistinctly crystalline masses, which decompose when heated into water and nitrogen.

Normal Ammonium Phosphate, (NH),PO.3H2O, is sometimes found in guano; it is also obtained by mixing a concentrated solution of hydrogen diammonium phosphate with water of ammonia. There are deposited small prismatic or acicular crystals, which decompose when exposed to the air, or when the solution is boiled.

Hydrogen Diammonium Phosphate, (NH4)2HPO4, is also found in some guanos, and is prepared by evaporating a solution of phosphoric acid with a slight excess of ammonia. The salt is deposited in transparent monoclinic prisms.

Dihydrogen Ammonium Phosphate, NH4H2PO4.-When the phosphoric acid is in slight excess with ammonia, crystals of this compound separate out.

Hydrogen Ammonium Sodium Phosphate, NaNH,HPO4.4H2O.-Microcosmic salt occurs in guano and in putrid urine. The salt is prepared by dissolving 5 parts of ordinary sodium phosphate, Na,HPO4.12H2O, in hot water, adding to a hot solution of the ordinary ammonium phosphate, (NH4)2HPO4, and allowing the solution to cool. The salt separates in transparent, monoclinic, prismatic crystals. They have a distinctly saline taste, and are readily soluble in water. On the application of heat the salt melts, gives off water and ammonia, and leaves a residue of the dihydrogen sodium phosphate; the further application of heat melts this salt to clear liquid with further loss of water, and with the formation of sodium hexametaphosphate, which forms a clear glass on cooling. Because of this property of forming a clear glass the salt is largely used in blowpipe analysis.

Ammonium Carbonate, NH,HCO3. NH,NH,CO,. Ammonii Carbonas, U. S. P.-As will be seen from the above formula, the official salt is a compound of the acid ammonium carbonate with ammonium carbamate. Normal ammonium carbonate, (NH4)2CO3, is obtained when the official salt is dissolved in water :

NH,HCO,.NH,NH,CO, + HẠO = NH1HCO + (NH4)2CO3.

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Acid
Ammonium

Carbonate.

Normal Ammonium

Carbonate.

When the normal carbonate is desired in quantity and in a solid form, the official compound is digested for 2 hours at a temperature of 12° with strong aqueous ammonia; the resulting white, crystalline powder is dried by pressing between folds of absorbent paper. These crystals are readily converted into the acid carbonate.

The official, which is also the commercial, salt is prepared by heating in iron retorts ammonium sulphate and calcium carbonate or chalk, with sometimes a small quantity of charcoal:

[blocks in formation]

After the condensation of the ammonium carbonate, the uncondensed vapors, containing water and ammonia, are led into sulphuric acid in order to recover the ammonia.

Crude ammonium carbonate may also be prepared by passing ammonia, liberated from gas-liquors by lime, into leaden chambers along with carbon dioxide and water.

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Water.

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Properties. The official ammonium carbonate occurs in "white, hard, translucent, striated masses, having a strongly ammoniacal odor without empyreuma, and a sharp, saline taste. On exposure to the air, the salt loses both ammonia and carbonic acid, becoming opaque, and is finally converted into friable, porous lumps, or a white powder." The salt is soluble in about 5 parts of water at 15°; it is decomposed by boiling water, with the elimination of carbonic acid and ammonia, resulting finally, after prolonged boiling, in complete dissipation of the salt. Alcohol dissolves the carbonate, leaving the acid carbonate behind. On the application of heat, ammonium carbonate is completely dissipated without darkening or charring. The aqueous solution reacts alkaline to litmus, and effervesces strongly with acids.

Hydrogen Ammonium Carbonate, NH4HCO,. Ammonium Bicarbonate.-Crystals of this salt have been found in Patagonian guano and in the purifiers of gas-works.

When the commercial carbonate is exposed to the air for some time a white powder results, consisting of the bicarbonate; it may also be prepared by passing carbon dioxide into an aqueous solution of the ordinary carbonate. It is usually found as a white, mealy powder, but may be obtained in large rhombic crystals by allowing them to form slowly from aqueous solution. At 60° it is slowly decomposed into ammonia, water, and carbon dioxide. The salt is soluble in 8 parts of water at 15°; it is insoluble in alcohol.

Symbol, Li.

LITHIUM.
Atomic Weight, 7.01.

Valence, I.

History. In 1817, Arfvedson, while working in the laboratory of Berzelius, found a peculiar substance in the mineral petalite from the Swedish iron-mines at Utö. The metal was first isolated by Bunsen and Matthiessen in 1855.

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Occurrence. While lithium is not found in large quantities, it is still widely distributed in the three kingdoms. In the mineral kingdom it is found in petalite, a silicate of aluminum, sodium, and lithium, to the extent of 2.7 to 3.7 per cent.; in lepidolite, a lithia mica, 1.3 to 5.7 per cent.; and in spodumene, a silicate of aluminum, sodium, and lithium, 3.8 to 5.6 per cent. It is found in a number of mineral waters, the most notable in the United States being the springs at Gettysburg. In the vegetable kingdom, lithium has been detected in the ash of the vine, of seaweed, and of tobacco. The animal kingdom contains small quantities of this metal, as shown by its detection in the ashes of blood and milk and in muscular tissue.

Preparation. In order to obtain metallic lithium, the chloride is first formed. This is accomplished by fusing at the highest temperature of a wind furnace 10 parts of finely-powdered lepidolite, 10 parts of barium carbonate, 5 parts of barium sulphate, and 3 parts of potassium sulphate. The heavy barium compounds settle to the bottom, while potassium and lithium sulphate remain at the top of the fused mass, and are extracted by water. The sulphates are converted into chlorides by the addition of barium chloride, the solution evaporated to dryness, and the lithium chloride separated from the potassium salt by solution in a mixture of absolute alcohol and ether.

The metal is obtained by fusing the chloride in a small porcelain crucible, and decomposing by an electric current from a zinccarbon battery of from four to six cells. The positive pole is a small piece of gas carbon, while the negative pole is an iron wire the thickness of a knitting-needle. In a few minutes the metal collects around this wire, and when it has attained the size of a pea, and before it becomes so large as to rise to the surface, it is lifted out by a spoon-shaped iron spatula, and cooled under naphtha.

Properties.-Lithium possesses the silver-white lustre of sodium and potassium, but does not tarnish by oxidation so easily as they do. It is the lightest of all known solids, having a specific gravity, according to Bunsen, of 0.5891 to 0.5983. It floats on ordinary petroleum, and can only be preserved under the lightest gasoline.

When heated to 180° lithium melts, and at a higher temperature ignites, and burns with a brilliant red flame. In contact with water it does not oxidize so actively as sodium, as not sufficient heat is evolved to melt it. Most of the acids act on it slowly, but concentrated nitric acid attacks it with explosive violence.

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