Inorganic Chemicals

Formula: NH4Cl; MW 53.49

Synonym: Sal ammoniac

Occurrence and Uses

Ammonium chloride occurs in nature in crevices near volcanoes. Also, it is found in smoke when burning dry camel or donkey dung as fuel. Important applications of this compound include the manufacture of dry cells for batteries; as a metal cleaner in soldering; as a flux in tin coating and galvanizing; in fertilizers; in pharmaceutical applications as a diuretic, or diaphoretic expectorant; and as an analytical standard in ammonia analysis. Also, it is used in freezing mixtures; washing powders; lustering cotton; in safety explosives and in dyeing and tanning.

Physical Properties

Colorless cubic crystals or white granular powder; saline taste; odorless; hygroscopic; does not melt but sublimes on heating at 340°C; vapor pressure 48.75 torr at 250°C and 251.2 torr at 300°C; density 1.5274 g/cm3 at 25°C; refractive index 1.642; readily dissolves in water, solubility: 229 g and 271 g/L solution at O°C and 20°C, respectively; solubility lowered by alkali metal chlorides and HCl; dissolution lowers the temperature of the solution; sparingly soluble in alcohols (6 g/L at 19°C) and soluble in liquid NH3; insoluble in acetone and ether.

Thermochemical Properties

ΔΗ°ƒ(s) –75.15 kcal/mol
ΔΗ°ƒ(s) [NH3(g) + HCl(g)] –41.9 kcal/mol
ΔG°ƒ(s) –48.51 kcal/mol
S° 22.6 cal/degree mol
Cρ 20.1 cal/degree mol
ΔH°subl (1 atm) 39.6 kcal/mol

Manufacture

Ammonium chloride is produced as a by-product in the Solvay process for manufacture of sodium carbonate:

NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl

NaHCO3 precipitate is filtered out of solution while NH4Cl is obtained by crystallization followed by washing and drying. Ammonium chloride also is produced from spent calcium chloride liquor obtained in ammonia-soda process:

CaCl2 + 2NH3 + CO2 + H2O → Na2SO4 + 2 NH4Cl

It also is made by heating a mixture of slight excess of NaCl solution with ammonium sulfate. The filtrate containing NH4Cl is concentrated and cooled.

NH4Cl crystallizes:

(NH4)2SO4 + 2NaCl → Na2SO4 + 2 NH4Cl

It is produced by direct neutralization reaction of NH3 and HCl combined as gaseous mixtures.

NH3(g) + HCl(g) → NH4Cl(s)

Reactions

NH4Cl is acidic in aqueous solution: the pH of 1%, 3%, and 10% solution at 25°C are 5.5, 5.1 and 5.0, respectively. (Merck 1996. The Merck Index, 12th ed. Rahway, NJ: Merck & Co.) It loses ammonia and becomes more acidic on prolonged exposure or storage. It reacts with iron, copper, nickel and other metals and some of their alloys such as bronze and brass. It reacts with alkalies forming NH3.

NH4Cl + NaOH → NH3 + NaCl + H2O

Ammonium chloride decomposes to ammonia and HCl when heated. The vapor resulting from sublimation consists of equal volume of NH3 and HCl, and does not consist of molecular NH4Cl. (Young, R. D. 1976. Ammonium Compounds. In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd. ed. Vol. 2, p. 52l. New York: Wiley Interscience.) Reacts with formaldehyde (neutralized with NaOH) forming examethylenetetramine
and HCl.

NH4Cl + 6 HCHO → C6H12N4 + 4HCl + 6H2O

Reaction with copper(II) chloride at 2:1 ratio produces yellow orthorhombic crystals of cupric ammonium chloride, which reacts with water to form blue dihydrate crystal, ammonium tetrachlorodiaquocuprate(II): heat 2NH4Cl + CuCl2 –––→ (NH4)2 + CuCl4 evaporation A similar complex formation occurs with mercuric chloride, zinc chloride, osmium chloride and platinum (II) and (VI) chlorides, forming mercuric ammonium chloride, (NH4)2•HgCl4, zinc ammonium chloride (NH4)3ZnCl4 or ZnCl2•3NH4Cl, osmium ammonium chloride, (NH4)2OsCl6, platinum ammonium chloride, (NH4)2PtCl4 and platinic ammonium chloride (NH4)2PtCl6, respectively. Similarly, it reacts with palladium chloride to form ammonium chloropalladate, (NH4)2PdCl4. It precipitates out ammonium platinichloride from solution of chloroplatinic acid (Archibald, E. H. 1920. J. Chem. Soc., 117, 1105):

H2PtCl6 + 2NH4Cl → (NH4)2PtCl6 + 2HCl

Neutralization reaction occurs with amide, forming chloride salt and ammonia:

NH4Cl + KNH2 → KCl + 2NH3

Heating with zirconium chloride gives a tetraamine adduct:

4NH4Cl+ZrCl4ZrCl4.4NH3+4HCl

Chemical Analysis

Elemental composition: Cl 66.28%, H 7.54%, N 26.18% Ammonium chloride is analyzed by treatment with formaldehyde (neutralized with NaOH) and the product HCl formed is analyzed by titration using an acid-base color indicator such as phenolphthalein. Alternatively, it may be mixed with caustic soda solution and distilled. The distillate may be analyzed for NH3 by titration with H2SO4; or by colorimetric Nesslerization; or with an ammonia-selective electrode (APHA, AWWA, WEF. 1995. Standard Methods for the Examination of Water and Wastewater. 19th ed. Washington, DC, American Public Health Association). The presence of ammonia or any other ammonium compound would interfere in the test. The moisture content in NH4Cl may be determined by Karl–Fischer method.

Formula : NH4CN; MW 44.056

Uses

NH4CN is used in organic synthesis. Unstable, it is not shipped or sold commercially.

Physical Properties

Colorless crystalline solid; cubic crystal; unstable; density 1.02 g/cm³; decomposes at 36°C; sublimes at 40°C; very soluble in cold water and alcohol; decomposes in hot water.

Preparation

Ammonium cyanide is prepared in solution by bubbling hydrogen cyanide into aqueous ammonia at low temperature:

HCN + NH3(aq) → NH4CN(aq)

It may be prepared in solution by the reaction of calcium cyanide and ammonium carbonate:

Ca(CN)2 + (NH4)2CO3 → 2NH4CN + CaCO3

or barium cyanide and ammonium sulfate:

Ba(CN)2 + (NH4)2SO4 → 2NH4CN + BaSO4

In dry state, NH4CN is made by heating a mixture of potassium cyanide or potassium ferrocyanide with ammonium chloride and condensing the vapors into ammonium cyanide crystals:

KCN + NH4Cl → NH4CN + KCl

Reactions

Ammonium cyanide decomposes to ammonia and hydrogen cyanide; often forming black polymer of HCN:

NH4CN → NH3 + HCN

It undergoes double decomposition reactions in solution with a number of metal salts. It reacts with glyoxal producting glycine (aminoacetic acid)

NH4CN + (CHO)2 → NH2CH2COOH + HCN

Reactions with ketones yield aminonitriles:

NH4CN + CH3COCH3 → NH2CH2CH2CH2CN + H2O

Analysis

Elemental composition: H 9.15%, C 27.23%, N 63.55%. NH4CN may be analyzed by heating the salt and trapping the decomposed products HCN and ammonia in water at low temperatures. The aqueous solution is analyzed for cyanide ion by silver nitrate titrimetric method or an ionselective electrode method; and ammonia is measured by titration or electrode technique (Patnaik, P. 1997. Handbook of Environmental Analysis, Boca Raton, FL: Lewis Publishers).

Toxicity

The solid or its solution is highly toxic. Ingestion can cause death. Exposure to the solid can be harmful as it decomposes to highly toxic hydrogen cyanide and ammonia.

Formula : (NH4)2Cr2O7; MW 252.10

Synonym : ammonium bichromate

Uses

Ammonium dichromate is used in pyrotechnics; in photoengraving and lithography; as a source of pure nitrogen in the laboratory; and as a catalyst.

Physical Properties

Bright orange-red monoclinic crystals; odorless; hygroscopic; decomposes at 180°C; density 2.115 g/cm³ at 25°C; readily dissolves in water (26.67 g/100 g at 20°C).

Preparation

(NH4)2Cr2O7 may be prepared by the reaction of ammonia gas with chromic acid:

2NH3 + 2CrO3 + H2O → (NH4)2Cr2O7

or ammonium sulfate with sodium dichromate:

(NH4)2SO4 + Na2Cr2O7 → (NH4)2Cr2O7 + Na2SO4

Reactions

(NH4)2Cr2O7 decomposes at 180°C. On further heating to 225° C it begins to swell and dissociates exothermically, liberating nitrogen and water vapor, leaving behind a residue of chromium(III) oxide:

(NH4)2Cr2O7→N2+Cr2O3+4H2O

As an acid salt, its solution is acidic (pH 3.45 and 3.95 for a 10% and 1% solution, respectively). It undergoes acid reactions. Also, it undergoes double decomposition reactions, forming metal dichromates:

(NH4)2Cr2O7 + Pb(NO3)2 → PbCr2O7 + 2NH4NO3

As an oxidizing agent, it undergoes oxidation-reduction reactions with reducing agents at ambient and elevated temperatures.

Hazard

Ammonium dichromate is an irritant to skin. Inhalation of dusts can cause pulmonary irritation, perforation of the nasal septum and “chrome sores.” Ingestion can cause ulceration. It is also a flammable salt.

Formula : NH4F; MW 31.04

Synonyms : neutral ammonium fluoride; normal ammonium fluoride

Uses

is used for etching glass; for preserving wood; as a mothproofing agent; in printing and dyeing textiles; and as an antiseptic in brewery

Physical Properties

White, deliquescent, crystalline solid; occurs in various forms, as granular powder (commercial products), needles or leaflets, or hexagonal prism (formed on sublimation and condensation); density 1.009 g/cm³ at 25°C; decomposes on heating; highly soluble in cold water (100g/100g at 0°C); decomposes in hot water; slightly soluble in alcohol, insoluble in liquid ammonia

Thermochemical Properties

Preparation

is made by passing ammonia gas through a 40% aqueous solution of hydrofluoric acid (ice-cooled):

Alternatively, it may be prepared by heating ammonium chloride with excess sodium fluoride. Ammonium fluoride is obtained by sublimation.

Also, it may be prepared by mixing an equimolar amount of aqueous ammonia and ammonium bifluoride.

Reactions

Decomposes on heating to ammonia and hydrogen fluoride; also decomposes in hot water producing ammonia and ammonium bifluoride:

The solution is acidic; it reacts with weak bases forming double salts; i.e., ammonium hexafluoroaluminate, ammonium hexafluorophosphate, ammonium hexafluorosilicate, ammonium hexafluorogallate,

Chemical Analysis

Elemental composition : F 51.30%, H 10.88%, N 37.82%. A measured amount is dissolved in water and the aqueous solution diluted appropriately and analyzed for fluoride by fluoride ion-selective electrode, or by ion chromatography. Ammonium ion (or liberated ammonia) is analyzed by titration or by ammonium ion-specific electrode (see Ammonia).

Toxicity

is a highly toxic substance; ingestion can cause nausea, vomiting, abdominal pain, tremor, hemorrhage, muscular weakness, convulsions and vascular collapse. Ingestion of large quantity can cause death. Chronic effects include mottling of enamel, osteoclerosis and calcification in ligaments.

Formula : HCCOONH4; MW 63.06;

Synonym : formic acid ammonium salt

Uses

Ammonium formate is used in chemical analysis to separate base metals from noble metal salts.
Physical Properties White monoclinic deliquescent crystals or granules; density 1.280 g/cm³; melts at 116°C; highly soluble in water (102 g/100 g at 0°C), solubility rapidly increasing with temperature (i.e., 531 g/100 g at 80°C); soluble in liquid ammonia, alcohol and ether.

Preparation

is prepared by the reaction of ammonia with formic acid:

or from methyl formate and ammonia:

Reactions

Thermal dissociation produces ammonia, carbon dioxide, and water; reacts with metal salts forming their formates; oxidized by strong oxidants forming carbon dioxide, water, and oxides of nitrogen.