The manufacture of sal ammoniac is usually a distinct business, and is carried on to a very great extent in the neighbourhood of London. Indeed, the London makers now supply the chief portion of that used in England. A large quantity is now, however, made at Manchester and Liverpool. A small quantity is imported from Germany. That from Brunswick is in the form of sugar-loaves. An inferior quality is also imported, in chests, from the East Indies. The red bands frequently seen in the sal ammoniac of commerce are said to arise from the workmen falling asleep, and allowing the fire to go down, and then suddenly raising the heat too high. (Muspratt.) They consist chiefly of ammonio-chloride of iron. =Ammonium, Citrate of.= (NH_{4})_{2}HC_{6}H_{6}O_{7}. _Syn._ DIAMMONIUM CITRATE, CITRATE OF OXIDE OF AMMONIA; AMMON′′NIÆ CIT′RAS, L. _Prep._ A concentrated solution of pure citric acid, gently heated, is saturated with sesquicarbonate of ammonium, in fine powder (about 7 parts to 6), and slightly in excess; and the resulting liquid is crystallised by refrigeration in close vessels, or by evaporation in vacuo. If heat be employed in the evaporation of the solution, an acid citrate will be formed. _Uses, &c._ Chiefly as a chemical test. An extemporaneous citrate, made with lemon-juice and drunk effervescing, is employed as a saline draught, and a mild aperient and diaphoretic, in fevers, &c. =Ammonium, Ferrocyanide of.= (NH_{4})_{4} FeC_{6}N_{6} . 3Aq. _Syn._ FERROCYANATE D’AMMONIAQUE, Fr. _Prep._ 1. Saturate a solution of hydroferrocyanic acid with sesquicarbonate of ammonium, in slight excess; evaporate the solution at a heat below ebullition, and crystallise by refrigeration. 2. Digest ferrocyanide of lead or of iron in a solution of sesquicarbonate of ammonium, at a gentle heat, for some time; then filter, evaporate, and crystallise. _Prop., &c._ It is isomorphous with ferrocyanide of potassium; it is easily crystallisable, very soluble in water, and is decomposed by ebullition. =Ammonium, Iodide of.= NH_{4}I. _Syn._ HYDRIODATE OF AMMONIA; AMMO′′NII IODI′DUM, L.; HYDRIODATE D’AMMONIAQUE, Fr. _Prep._ An aqueous solution of hydriodic acid is neutralised with ammonia, or ammonium sesquicarbonate, in slight excess; and the resulting liquid is either carefully, but rapidly, evaporated to dryness over a water bath, or it is concentrated by the same means, and then caused to deposit crystals by refrigeration; in both cases care is taken to keep a slight excess of ammonia present during the evaporation. The crystals are dried by pressure between folds of bibulous paper; and the product, in either form, preserved in a stoppered bottle.