AMMONIA, Anhydrous (NH,).—Priest ley, in 1774, was the first to isolate ammonia, having collected it over mercury. Scheele, in the same year, discovered that it contained ni trogen. Its true composition was determined by Berthollet in 1785. Liquid ammonia, however, was first obtained by Faraday, in 1823, by warming the compound 2AgC13NH, in a sealed tube.
Physical Properties.— Colorless, with pungent odor, strongly alkaline taste, and has alkali reactions. Molecular weight, 17.03.
Specific gravity, calculated, 0.5883; spe cific gravity, observed, 0.5962; specific gravity of liquid, 0.6234.
Melting point, --77.34° C.
Boiling point, C.
Critical temperature, —130° C. (Dewar); critical pressure, 115 atmospheres (Dewar).
Coefficient of expansion at constant pres sure, 0-100° C., 760 mm., .003800; at 0° C., 760 mm., .00386; coefficient of pressure at constant volume, 0° C., 760 mm., .003800; at C., 760 mm., .003770.
Specific heat, 0.5009 at C.; 0.5317 at 100° C.; 0.5629 at 200° C.; 0.5202 between 23 100° C.
Heat of formation of gas, 11,887 calories; in solution, 20,322 calories.
Heat of formation of gas, at 15° C., 12,200, and of liquid 16,600 (Chem. Kalendar).
Heat of absorption in water, 8,435 calories.
Weight of one liter, calculated, 0.7606 grams; observed, 0.7708 grams; weight of one cubic foot at 32° F., 29.92" pressure, .04812 lbs.
Solubility in water (Roscoe and Ditt mar). Grams of ammonia in one gram of water. At 0° C., 0.875; 10° C., 0.679; 20° C., 0.526; 30° C., 0.403; 40° C., 0.307; 50° C., 0.229.
Latent heat of evaporation, being higher than that of any other known liquid except water, is 5,000 cal. at 15° C. and 5,600 cal. at boiling point. Hence the use of ammonia for refrigeration.
Chemical Properties.— Ammonia is poison ous and attacks the mucous membrane. Seri ous effects on human beings are experienced when the atmosphere in which they are has a greater quantity of ammonia than five one hundredths of 1 per cent. Ammonia will not burn in air at ordinary temperature, but will do so when heated, and burns still more readily when mixed with oxygen. With the aid of catalysts (copper, iron, nickel, and especially platinum), ammonia is oxidized by oxygen or air at low temperatures. At atmospheric pres sure ammonia begins to decompose below 500° C., the rapidity of decomposition varying with the nature of the surfaces with which it is in contact, glass being inactive but oorcelain and many metals and oxides accelerating, decompo sition being nearly complete when the latter are present. Ammonia is very soluble in water, alcohol, ether and many saline solutions. The aqueous solution of ammonia is strongly alka line and unites with acids to form salts.
How Obtained.— Ammonia occurs mostly in combination with acids, but is found in a free state in fumaroles of Monti Carboli in Tuscany, which also contain ammonium sul phate and borate. It is present in the air to the extent of one hundred parts of ammonia to one million parts of air. For laboratory pur poses it can be obtained by the action of cal cium oxide on ammonium chloride. A mixture of hydrogen and any oxide of nitrogen, passed over a heated porous body, such as spongy platinum, pumice, or ferric oxide, produces ammonia. It may also be produced by passing
moist nitric oxide over hot iron filings; and also by heating solutions of nitrates or ni trites with caustic alkali and zinc.
Laboratory Methods of Preparation.—(l) By gently warming the aqueous solution of ammonia and passing the gas over quicklime. (2) From lime and an ammonia salt (e.g., chloride or sulphate) by heating together in a retort.
Ammonia is a decomposition product of the decay or destructive distillation of nitrogenous organic matter.
Commercial Methods of Preparation.— I. DESTRUCTIVE DISTILLATION PROCESSES. 1. By-product in Manufacture of Illuminating When coal is destructively distilled as in the production of coal gas for illuminating pur poses, a number of extremely valuable by-prod ucts are obtained such as benzol, toluol, am monia, phenol, tar, coke, etc. Until some years ago the greatest part of die ammonia produ 'ion of the world was obtained from the ammo niacal liquors of gas works. These liquors are distilled with excess of slaked lime with the aid of steam (in coils) in stills provided with rectifying columns for concentrating the am monia gas. The latter is scrubbed by passing successively through towers containing caustic soda solution and paraffin oil, and is thus freed from impurities, such as H,S, CO, and pyri dine basis. The purified ammonia gas is then converted to ammonium sulphate, or to aqua ammonia by absorption in distilled water. A small amount of ammonia is made from the materials used in purifying illuminating gas (freeing the latter from H,S and cyanogen compounds). The purifying material, (spent oxide° or (Bueb or Feldmann process) contains a large percentage of combined am monia which is recovered by gas works or manufacturers who purchase this material from gas plants.
2. By-product in Manufacture of Coke for Metallurgical Use.— Until recently, most of the coke required for metallurgical purposes (espy daily in the manufacture of iron and steel) was made by the distillation of coal in bee-hive ovens in which all the valuable volatile in gredients of the coal were lost. Now, how ever, particularly since the great demand for coal tar products of all kinds caused by the World War, an increasingly large percentage of coke is being made in by-product coke ovens in which the gaseous and liquid distillates from the coal are recovered and used or sold.
Similarly in some countries (e.g., Scotland) in which blast furnaces have been operated with coal instead of coke the recovery of the volatile ingredients of the coal has met with commercial success.
3. is the Distillation of the Bi tuminow In Scotland where this in dustry has had a large development, and to some extent in this country, the recovery of ammonia has been successfully carried out. About 42 pounds of ammonium sulphate are recovered from one ton of Scotch shale.
4. in the Manufacture of Glue. —After glue has been extracted from animal substances, like bones, cartilages, hoofs and horns the residue is destructively distilled, yielding among other products ammonia as a valuable by-product.