CHLORIDE OF AMMONIUM. 2 457 formation of bisulphide of ammonium, whilst a hyposulphite of ammonium is produced in the liquid; 8 H,NHS + 502 = 2 [(H ̧N)2S2] +2 [(H ̧N)‚§‚H‚Ð ̧]+2 H2O. A solution of sulphhydrate of ammonium dissolves the sulphides of the electro-negative metals as readily as the protosulphide of ammonium does, but sulphuretted hydrogen is liberated: for example, 6 H ̧NHS + As2S =2 [(H ̧N) ̧As$ ̧]+3 H2S. Sulphhydrate of ammonium may be obtained in the anhydrous form, by mixing dry sulphuretted hydrogen with dry ammoniacal gas; 2 volumes of ammonia combine with 2 of sulphuretted hydrogen, and condense in yellowish, transparent, brilliant plates, which are very volatile, and sublime without decomposition; they are very soluble in water. (617) CHLORIDE OF AMMONIUM (H1NCl=53'5); Sp. Gr. of Solid, 1578; of Vapour, 089; Mol. Vol. of Vapour, Composition in Ico parts, HCl, 68·22; H2N, 3178.-Muriate of Ammonia, or Sal Ammoniac as it is commonly termed, is the most important of the salts of ammonium. It may be formed directly by the union of hydrochloric acid and ammoniacal gases: it was formerly imported from Egypt in considerable quantity as a product of the distillation of dried camel's dung, but in this country it is now furnished almost entirely from ammoniacal liquor, a waste product from the coal-gas works. Coal contains a portion of nitrogen, which, during the process of distillation, is partially converted into ammonia; this combines with carbonic acid and with sulphuretted hydrogen: these compounds are condensed with the gas liquor from which the ammonia is subsequently extracted. The best process for preparing sal ammoniac consists in neutralizing the gas liquor with hydrochloric acid. For this purpose the liquid is pumped up from a tank into the decomposer,—a large wooden vat closely fitted with a cover, connected with flues for carrying off the gaseous products; the acid in suitable quantity is placed in jars, from which it is slowly drawn off by siphons, and is thus allowed to mix gradually with the liquor; abundance of gas is disengaged, and is made to pass through a fire, where the sulphuretted hydrogen is burned: much of the tarry matter (derived from the coal) which was held in solution, is deposited during this operation, and the liquid froths up considerably, any loss which might be thus occasioned being prevented by the use of a *The vapour-volume of this and of several of the salts of ammonium, including the hydrobromate and hydrocyanate, is anomalous, being double that of most compounds. Many chemists consider that in the act of evapora tion the acid and base are dissociated (Part I. note, p. 100) in these salts. 458 : CHLORIDE OF AMMONIUM, OR SAL AMMONIAC. waste-pipe, by which the overflow is carried back into the tank below. When the liquor has thus been neutralized, it is run into a covered evaporating pan, where the remaining portions of sulphuretted hydrogen are expelled; after further concentration it is drawn off into shallow wooden vessels, lined with lead, to crystallize the crystals thus procured are drained, and the mother-liquor is again concentrated. The rough crystals are next heated in a cast-iron pan, to a point approaching that at which sublimation commences; a good deal of tarry matter, which the salt still retains, is expelled during this roasting. The salt is then sublimed in a strong cylindrical iron pot, furnished with a leaden or iron cover lined with fire-clay; the fire underneath is gradually raised, and the salt sublimes and is deposited in large dome-shaped cakes on the inner surface of the cover. The liquors which are condensed during the distillation of bones in closed iron cylinders, in the process of preparing animal charcoal, are highly charged with an impure carbonate of ammonium, contaminated with volatile oily and tarry products derived from the action of heat upon animal matter: these liquors furnish a source of ammoniacal salts of some importance: formerly this liquid, after being subjected to a partial purification, was commonly known as spirit of hart's-horn, because a similar liquor was originally obtained by the distillation of horn shavings. Sublimed chloride of ammonium forms semi-transparent, tough, fibrous masses. It is very soluble in water, 100 parts of which at 60° dissolve 36 parts, and at the boiling-point, 88-9 parts of the salt a great reduction of temperature occurs whilst it is undergoing solution, and it is hence employed as a common ingredient in freezing mixtures; it crystallizes usually in an arborescent form, but sometimes in cubes and octohedra. Sal ammoniac has a sharp, acrid taste; it is slightly soluble in alcohol. When heated, it sublimes much below redness, before undergoing fusion. It has a strong tendency to form double salts with the chlorides more. electro-negative than itself. The compounds of many metals which form volatile chlorides, such as the arseniates and arsenites, the antimoniates and the stannates, when heated with chloride of ammonium, lose the arsenic, antimony, and tin in the form of chlorides of these metals; and the salts of lead, iron, zinc, and aluminum, are decomposed and completely volatilized when ignited with a large excess of chloride of ammonium. Rose observed that all the basic protoxides of the form N", such as protoxides of iron, cobalt, and manganese,-and oxides of the form N,O, such as suboxide of copper, also decompose chloride of ammonium, when SULPHATE AND NITRATE OF AMMONIUM. 459 heated with its solution, the ammonia being displaced by the metallic oxide, and a fixed metallic chloride being formed, whilst not one of the sesquioxides has this power. (618) SULPHATE OF AMMONIUM [(H1N)2SO=132, or H1NO, SO,=66; Sp. Gr. 1·695] is prepared in large quantity by subjecting gas liquor to distillation, and condensing the volatilized ammonia in sulphuric acid. The salt crystallizes out from the strongly acid liquor, which is employed to condense fresh ammonia in subsequent operations. On a small scale it may be obtained in a pure form by adding sesquicarbonate of ammonium to dilute sulphuric acid so long as any effervescence ensues. It crystallizes in flattened prisms, which are isomorphous with those of sulphate of potassium: it is soluble in twice its weight of cold water, and has a sharp disagreeable taste; when heated it decrepitates, at 284° it melts, and between 500° and 600° it undergoes partial decomposition, sulphite of ammonium being among the products. It forms a great number of double salts isomorphous with the corresponding salts of potassium. Sulphate of ammonium has lately been applied to muslins and other fabrics for the purpose of preventing them from burning with flame in case they should accidentally take fire. The finished goods are dipped into a solution containing 10 per cent. of the salt, and dried in a centrifugal machine, or hydro-extractor. An acid sulphate may be formed which has the formula [(H,N),H 2 SO1], and a double sulphate of sodium and ammonium (H1NNaSO4, 2 H2O) may be readily formed by mixing solutions of the two salts, and evaporating the liquid till it begins to crystallize. (619) NITRATE OF AMMONIUM (HANNO,, or H,NO,NO.= 80); Sp. Gr. 1·635.-This is a salt of some importance to the chemist, as it furnishes him with a ready source of pure nitrous oxide. It is procured by neutralizing nitric acid with a solution of sesquicarbonate of ammonium: on evaporation, the salt crystallizes in long striated anhydrous prisms; by rapid evaporation it is obtained either in a fibrous or in an amorphous mass. It has a bitter acrid taste, is somewhat deliquescent, and during the act of solution causes a great depression of temperature, hence it is often used in frigorific mixtures: when heated to 226° it melts, and at 480° it undergoes complete decomposition, being converted into nitrous oxide and water, in the manner already described (364); H1NN→ ̧=N ̧‡+2 H2O. If thrown on a redhot plate it melts, hisses, and is dispersed with a faint bluish flame. (620) CARBONATES OF AMMONIUM.-Neutral carbonate of am 3 460 SESQUICARBONATES OF AMMONIUM. 2 monium is not known in the solid form. When carbonic anhydride and dry ammonia are mixed, no matter in what proportions, 2 volumes of ammonia and 1 of carbonic anhydride unite, and are condensed into a white solid, carbamate of ammonium being formed according to Gerhardt, 2 H,N+60,=H,NH2NCO2. This compound is rapidly converted by water into neutral carbonate of ammonium: H,NH,NCO2+ H2O=(H ̧N),ЄÐ ̧. There are, however, several compounds of ammonium with carbonic acid. The most important of these is the sesquicarbonate, the common carbonate or smelling-salts of the shops (2[(H1N),€Ð ̧]EO,=236, or 2 H1NO,3 CO2=118); Composition in 100 parts, H ̧N, 28·81; ¤Ð„, 55'93; H2Ð,15·26. It is usually obtained as a semi-transparent fibrous mass, by mixing chalk with half its weight of sulphate, or of chloride of ammonium, collecting in leaden vessels the crude product which comes over on applying heat, and resubliming the mixture at a temperature of about 150° F.; the salt is received in leaden hoods, in the interior of which it is deposited. During this process a large quantity of free ammonia escapes, because the neutral carbonate of ammonium cannot exist at that temperature. The decomposition of the chloride of ammonium may be represented thus:: 6H ̧NC1+3 €a¤¤ ̧=3¤aCl,+2 [(H ̧N),¤Ð ̧]¤Ð2+2 H2N+H2Ð. The sesquicarbonate of ammonium has a strong, pungent smell, like that of pure ammonia, arising from the continual volatilization of carbonic ammonide at ordinary temperatures: 2 [(H ̧N),¤¤ ̧]¤Ð, becoming 2 (H,NH¤Ð ̧)+(H ̧N),¤Ð ̧. Owing to this loss of ammonia the salt speedily becomes coated with a white spongy crust of bicarbonate. If the powdered salt be placed upon a filter, and washed with successive small quantities of cold water, the neutral carbonate may be gradually dissolved away, and bicarbonate of ammonium, which is a more sparingly soluble salt, will be left upon the filter. The sesquicarbonate has an acrid taste and a strongly alkaline reaction. In its ordinary form the sublimed salt has a composition which is exceptional, since in order to convert it into a normal sesquicarbonate it would require an additional atom of water, which is never found in the commercial salt; but its aqueous solution, if saturated and exposed to a temperature of 32°, deposits large, transparent octohedra with a rhombic base, of the true hydrated sesquicarbonate [(HN), H2 3 CO3, 2 H,0]. According to the researches of Rose there are PHOSPHATES OF AMMONIUM—AMMONIATED SALTS. 461 several compounds resulting from the combination of the carbonate with different proportions of bicarbonate of ammonium. The Acid Carbonate or Bicarbonate of Ammonium (H1NH ЄÐ ̧ =79; Sp. Gr. 1586) is isomorphous with the corresponding potassium salt: it is soluble in 8 parts of cold water, and if the solution be heated, carbonic acid escapes; when exposed to the air the dry salt becomes slowly volatilized. It may be obtained in large transparent prismatic crystals, derived from a rhombic octohedron [4 (H2NHЄÐ ̧)H2O], by pouring boiling water upon the sesquicarbonate, corking the flask, and allowing it to cool. It is sometimes formed spontaneously during the decomposition of guano, and is then deposited in large regularly formed crystals. Carbonate of ammonium combines with many metallic carbonates, forming double salts. 5 4 2 (621) PHOSPHATES OF AMMONIUM, corresponding to those of sodium, may be formed; but the only one of any importance is the tribasic phosphate of sodium ammonium and hydrogen, known as microcosmic salt (NaH NH,PO ̧ . 4 H2O, or NaO,H,NO,HO, PO,.8 HO=137+72). It is prepared by mixing a hot solution of 6 parts of phosphate of sodium with a solution of I part of chloride of ammonium in the smallest possible quantity of water; common salt remains in solution, and the phosphate crystallizes in large transparent prisms, which are efflorescent in a dry air. It may be purified by a second crystallization from a small quantity of hot water to which a little free ammonia has been added, to compensate for the loss of ammonia which the salt sustains when heated in solution. By ignition, all the ammonia and water are expelled, metaphosphate of sodium remains, and fuses into a colourless glass at a red heat. This salt is sometimes employed as a flux for experiments with the blowpipe, as the glass dissolves many metallic oxides, and forms transparent beads, from the colour of which the presence of certain metals can in many cases be ascertained. (622) Ammoniated Salts.-Anhydrous ammonia enters into combination with many anhydrous metallic salts in a manner somewhat analogous to that of water of crystallization. In other cases, salts which usually retain water of crystallization lose it either partially or entirely when they combine with ammonia, but the number of atoms of ammonia is not influenced by the proportion of water with which the salt generally unites. Chloride of silver, of tin, of copper, and of calcium, sulphate of copper, and of zinc, nitrate of silver, and of copper, form compounds of |