Hydrochloric acids

Hydrochloric acid is obtained from four major sources  

As a by-product in the chlorination of both aromatic and aliphatic hydrocarbons or from the thermal degradation of organic chlorine compounds, 

From reacting sodium chloride (salt) and sulfuric acid, 

Hydrochloric acid is replacing sulfuric acid in some applications such as metal pickling, which is the cleaning of metal surfaces by acid etching. It leaves a cleaner surface than sulfuric acid, reacts more slowly, and can be recycled more easily. It is used in chemical manufacture especially for phenol and certain dyes and plastics. In oil well drilling, it increases the permeability of limestone by acidifying the drilling process. 

CHEMICAL NAME = hydrochloric acid CAS NUMBER = 7647-01-0 MOLECULAR FORMULA = HCl(aq) 

Hydrochloric acid is used in numerous applications, but it is generally obtained indirectly as a by-product in other chemical processes. The first large-scale production of hydrochloric acid resulted from the mass production of alkalis such as sodium carbonate (Na C ) and potassium carbonate (potash, K2C03). The depletion of European forests and international disputes made the availability of alkali salts increasingly uncertain during the latter part of the 18th century. This prompted the French Academy of Science to offer a reward to anyone who could find a method to produce soda ash from common salt (NaCl). Nicholas LeBlanc (1743—1806) was credited with solving the problem. LeBlanc proposed a procedure in 1783 and a plant based on LeBlanc s method was opened in 1791. LeBlanc s method uses sulfuric acid and common salt 

PhEur Acidum hydrochloridum concentratum USPNF Hydrochloric acid 

Chlorohydric acid concentrated hydrochloric acid E507. 

Hydrochloric acid is widely used as an acidifying agent, in a variety of pharmaceutical and food preparations (see Section 16). It may also be used to prepare dilute hydrochloric acid, which in addition to its use as an excipient has some therapeutic use, intravenously in the management of metabolic alkalosis, and orally for the treatment of achlorhydria. See Section 17. 

Hydrochloric acid occurs as a clear, colorless, fuming aqueous solution of hydrogen chloride, with a pungent odor. 

The JP 2001 specifies that hydrochloric acid contains 35.0-38.0% w/w of HCl the PhEur 2005 specifies that hydrochloric acid contains 35.0-39.0% w/w of HCl and the USPNF 23 specifies that hydrochloric acid contains 36.5-38.0% w/w of HCl. See also Section 9. 

DOT Label Corrosive Material, UN 1050 Formula HCl MW 36.46 CAS [7647-01-0] Composition Hydrochloric acid is an aqueous solution of the gas hydrogen chloride reagent-grade concentrated acid contains 38% HCl by mass (normality 11-12) a constant-boiling acid (an azeotrope with water) contains about 20% HCl. 

Hydrogen chloride is a fire-effluent gas. Firefighters are frequently exposed to significant concentrations of HCl (Brandt-Rauf et al. 1988). Large amounts of HCl are 

Pure acid is a colorless and fuming liquid with a pungent odor. Dissolved iron imparts slight yellow coloration (Merck 1989). Density 1.20 for 36-38% acid, 1.1 for 20% acid [at 15°C (59°F)] constant-boiling 20% azeotrope boils at 108.6°C (227°F), freezes at — 114°C (—173°F) pH of 1 A solution is 

Concentrated hydrochloric acid is a corrosive substance that can cause severe bums. Spilhng into the eyes can damage vision. Ingestion can produce corrosion of the mouth, gastrointestinal tract, and stomach, and diarrhea. 

Rats exposed continuously to a hydrogen chloride atmosphere died after physical incapacitation (Crane et al. 1985). Hartzell and coworkers (1987) have studied the 

Most of the tables below are from Intemattorml Critical Tables, vol. 5, pp. 115-116, 122-125. 

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Andrews deration An important titration for the estimation of reducing agents. The reducing agent is dissolved In concentrated hydrochloric acid and titrated with potassium iodale(V) solution. A drop of carbon tetrachloride is added to the solution and the end point is indicated by the disappearance of the iodine colour from this layer. The reducing agent is oxidized and the iodate reduced to ICl, i.e. a 4-eiectron change. 

On acetylation it gives acetanilide. Nitrated with some decomposition to a mixture of 2-and 4-nitroanilines. It is basic and gives water-soluble salts with mineral acids. Heating aniline sulphate at 190 C gives sulphanilic add. When heated with alkyl chlorides or aliphatic alcohols mono- and di-alkyl derivatives are obtained, e.g. dimethylaniline. Treatment with trichloroethylene gives phenylglycine. With glycerol and sulphuric acid (Skraup s reaction) quinoline is obtained, while quinaldine can be prepared by the reaction between aniline, paraldehyde and hydrochloric acid. 

Its hydrochloride is prepared by heating morphine with hydrochloric acid under pressure. It is a potent emetic. 

M.p. 127 5°C. Dibasic, readily diazotizes. Prepared by treating hydrazobenzene with hydrochloric acid, intramolecular rearrangement taking place. 

Usually prepared by the action of NaCN on benzaldehyde in dilute alcohol. It is oxidized by nitric acid to benzil, and reduced by sodium amalgam to hydrobenzoin PhCHOHCHOHPh by tin amalgam and hydrochloric acid to des-oxybenzoin, PhCH2COPh and by zinc amalgam to stilbene PhCH = CHPh. It gives an oxime, phenylhydrazone and ethanoyl derivative. The a-oxime is used under the name cupron for the estimation of copper and molybdenum. 

CH2CI-CO-CH3. Colourless lachrymatory liquid b.p. 119°C. Manufactured by treating propanone with bleaching powder or chlorine. It is used as a tear gas and is usually mixed with the more potent bromoacetone. chloro acids Complex chloroanions are formed by most elements of the periodic table by solution of oxides or chlorides in concentrated hydrochloric acid. Potassium salts are precipitated from solution when potassium chloride is added to a solution of the chloro acid, the free acids are generally unstable. 

Clemmensen reduction Aldehydes and ketones may generally be reduced to the corresponding hydrocarbons by healing with amalgamated zinc and hydrochloric acid. 

CH2CI2. A colourless liquid with a chloroform-like odour b.p. 4I°C. Prepared by heating chloroform with zinc, alcohol and hydrochloric acid manufactured by the direct chlorination of methane. Decomposed by water at 200°C to give methanoic and hydrochloric acids. Largely used as a solvent for polar and non-polar substances, particularly for paint removal (30%), dissolving cellulose acetate and degreasing (10%). It is more stable than carbon tetrachloride or chloroform especially towards moisture or alkali. It is somewhat toxic. U.S. production 1981 280000 tonnes. 

Doebner-von Miller reaction Condensation of an aromatic amine with an aldehyde or ketone in the presence of hydrochloric acid to form a quinoline derivative. A general method, thus aniline and ethanal give 2-methyl-quinoline (quinaldine) and p-phenetidine. 

Dow process The process for the extraction of magnesium from sea-water by precipitation of Mg(OH)2 by Ca(OH)2 followed by solution of the hydroxide in hydrochloric acid. 

Fischer-Hepp rearrangement The nitros-amines of aromatic secondary amines when treated with hydrochloric acid give nuclear substituted nitrosoamines. Among the benzene derivatives, if the para position is free the -NO group displaces the hydrogen atom there in naphthalene derivatives it enters the 1-position ... 

GattermaDD synthesis A method for the synthesis of aromatic hydroxyaldehydes. E.g. AICI3 is used to bring about the condensation of phenol with a mixture of gaseous hydrochloric acid and hydrocyanic acid an aldimine hydrochloride is formed and on hydrolysis gives p-hydroxybenzaldehyde... 

Hoesch synthesis A variation of the Gattermann synthesis of hydroxy-aldehydes, this reaction has been widely applied to the synthesis of anthocyanidins. It consists of the condensation of polyhydric phenols with nitriles by the action of hydrochloric acid (with or without ZnCl2 as a catalyst). This gives an iminehydrochloride which on hydrolysis with water gives the hydroxy-ketone. 

CHi=CMeCOOH. Colourless prisms m.p. 15-16 C, b.p. 160-5 C. Manufactured by treating propanone cyanohydrin with dilute sulphuric acid. Polymerizes when distilled or when heated with hydrochloric acid under pressure, see acrylic acid polymers. Used in the preparation of synthetic acrylate resins the methyl and ethyl esters form important glass-like polymers. 

Molisch s test A general test for carbohydrates. The carbohydrate is dissolved in water, alcoholic 1-naphthol added, and concentrated sulphuric acid poured down the side of the tube. A deep violet ring is formed at the junction of the liquids. A modification, the rapid furfural test , is used to distinguish between glucose and fructose. A mixture of the sugar, 1-naphthol, and concentrated hydrochloric acid is boiled. With fructose and saccharides containing fructose a violet colour is produced immediately the solution boils. With glucose the appearance of the colour is slower. 

CH2 CH C CH. Colourless gas with a sweet odour b.p. 5°C. Manufactured by the controlled low-temperature telomerization of ethyne in the presence of an aqueous solution of CuCI and NH Cl. Reduced by hydrogen to butadiene and, finally, butane. Reacts with water in the presence of HgSO to give methyl vinyl ketone. Forms salts. Forms 2-chloro-butadiene (chloroprene) with hydrochloric acid and certain metallic chlorides. 

Colourless crystals m.p. 50 C, b.p. 301 C. Basic and forms sparingly soluble salts with mineral acids. Prepared by the reduction of 1-nitronaphthalene with iron and a trace of hydrochloric acid or by the action of ammonia upon l-naphlhol at a high temperature and pressure. 

N-phenylhydroxylamine, PhNHOH and further reduction can give azoxybenzene, azobenzene, hydrazobenzene and aniline. The most important outlet commercially for the nitro-compounds is the complete reduction to the amines for conversion to dyestufTs. This is usually done in one stage with iron and a small amount of hydrochloric acid. 

Ditrophenol, -nitropbenol, C H NOj. Colourless needles m.p. 114 C. Prepared as 2-nitrophenol. Reduction with iron and hydrochloric acid gives 4-aminophenol. 

Prepared by mononilrating toluene, as a 40% constituent of the mixture of isomers. It is reduced to p-toluidine with iron and hydrochloric acid. 

CfiHgNj. Colourless crystals m.p. 63 C, b.p. 2%TC. Turns brown in air. Prepared by a one-stage reduction of m-dinitrobenzene with iron and hydrochloric acid. 

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