Benzoic acid

description

Benzoic acid is the simplest member of the aromatic carboxylic acid family. It is a weak acid that is a precursor for the synthesis of many important organic compounds. More than 90 percent of commercial benzoic acid is converted directly to phenol and caprolactam. Its use in the production of glycol benzoates for the application of plasticizer in adhesive formulations is increasing. The organic compound is also used in the manufacture of alkyd resins and drilling mud additive for crude oil recovery applications. It is also used as a rubber polymerization activator, retardant, resins, alkyd paint, plasticizers, dyestuffs, and fibers. Benzoic acid and its esters occur in apricots, cranberries, mushrooms and jasmine plants. The history of benzoic acid dates back to sixteenth century. In the year of 1875 Salkowski a prominent scientist discovered its antifungal abilities. In medicine, benzoic acid is the principal component of benzoin resin, and is a constituent of Whitfield’s ointment which is used for the treatment of fungal skin diseases such as tinea, ringworm, and athlete’s foot.

Chemical Properties

Scaly or needle like crystals. With the smell of formaldehyde or benzene. Slightly soluble in water, soluble in ethanol, methanol, diethyl ether, chloroform, benzene, toluene, CS2, CCl4 and turpentine.

history

Benzoic acid was found in the 16th century. In 1556, Nostradamus first described carbonization effect of benzoin; After the Alexius Pedemontanus and Brian blessed decipher were discovered in 1560 and 1596. In 1875, the salkowski discovered the antifungal potency of benzoic acid, so benzoic acid is used for long term preservation cloudberry.

food preservatives

Benzoic acid and sodium benzoate are commonly used food preservative. In acidic conditions, it has inhibitory effect on yeast and mold. When pH value is 3 antibacterial strength, when pH was 6 for a lot of mould effect is very poor, so the inhibition the optimum pH value is 2.5-4.0. In the food industry with plastic barrels concentrated fruit and vegetable juice, the maximum usage shall not exceed 2.0g/kg; in the jam (not including canned), fruit juice (taste) drinks, soy sauce, vinegar in the maximum amount is 1.0g/kg; in Wine, candy, wine in the maximum amount of 0.8g/kg in the low salt; pickles, sauces, candied fruit, use the largest 0.5g/kg in carbonate; use the largest beverage 0.2g/kg. because of solubility of benzoic acid, when used will be stirring, or dissolved in a small amount of hot water or ethanol. The use of concentrated fruit juice in the soft drink used for benzoic acid easily volatile with steam, it is commonly used in the sodium salt. Benzoic acid in food industry is a common preservative in dairy products, but not allowed to be added. In general, benzoic acid is considered to be safe. But for some special populations, including infants, long-term intake of benzoic acid may lead to asthma, urticaria, metabolic acidosis and other adverse reactions. Paul deodorant benzoic acid is also used as a beverage. As the cream sweet perfume fragrance. Can also be used for chocolate, lemon, orange, sub berries, nuts, candied fruit and other edible flavor type. Tobacco flavor also commonly used. In addition of benzoic acid is also used as a pesticide, medicine, dye, mordant and plasticizer agent for the production of raw materials, polyamide resin and alkyd resin modifying agent and steel equipment anti rust agent.

Uses

1. Used as a chemical reagent and preservative.
2. Benzoic acid is important type food preservative. Under acidic conditions, It has inhibitory effects to mold, yeast and bacteria , but the effect is weak acid producing bacteria. The most appropriate antimicrobial pH values is ranging from 2.5 to 4, generally lower, the pH value is appropriate from 4.5 to 5. In the food industry with plastic barrels concentrated fruit and vegetable juice, the maximum use amount shall not be over 2.0g/kg; in jam (excluding canned), (taste) juice drink, soy sauce, vinegar in the maximum dose of 1.0g/kg; in soft candy, wine, wine in the maximum dose of 0.8 g/kg separately; in the low salt pickled vegetables, the sauce, candied fruit, maximum dose is 0.5 g/kg; in carbonated drinks in the largest amount of use is 0.2g/kg. due to benzoic acid, slightly soluble in water, its use can be a small amount of ethanol enable dissolved.
3.Preservative; anti microbial agents.
Due to the low solubility of benzoic acid and use shall be stirring, or dissolved in a small amount of hot water or ethanol. When used in the soft drink with fruit juice concentrate, for benzoic acid easy volatile with the water vapor, so often used in the sodium salt, besides the above sodium equivalent to benzoic acid 0.847g.
4.Often used as a fixative agent or preservative. Also used as a fruit juice aroma conservation agents. As a perfume with perfume fragrance. Can also be used for chocolate, lemon, orange, berries, nuts, candied fruit type edible essence. Tobacco flavor is also commonly used.
5.Benzoic acid and its sodium salt are food preservatives. Under acidic conditions, it has inhibition of yeasts and molds. When pH 3, antibacterial strength and when pH 6, many fungi effect is very poor, so the antibacterial optimum pH is 2.5-4.0. Benzoic acid is mainly used for the production of sodium benzoate preservatives, dyes intermediates, pesticides, plasticizers, mordant, medicine, spice and also can be used as alkyd resin and polyamide resin modifier for the production of polyester, terephthalic acid and used equipment, iron and steel anti rust agent.
6.Mainly used for antifungal and antiseptic.
7.Used in medicine, dye carriers, plasticizer, spices and food preservatives such as production, and can also be used to paint of alkyd resin performance improvement; used as pharmaceutical and dye intermediates, used for the preparation of plasticizer and spices etc., as well as equipment, iron and steel anti rust agent.

Hazard

Benzoic acid accumulation is less, low toxicity in the body involved and metabolism. If the excessive consumption of benzoic acid, the body's liver and kidney will be jeopardized. Maximum safety of carbonated drinks of benzoic acid usage is 5mg/kg of body weight, then calculated according to the weight of 60kg, daily limit is 300mg, benzoic acid for carbonated drinks, the maximum amount of use is 0.2g/kg, then drank 1.5kg of beverage is safe.
It has strong toxic effects on microorganisms, but the toxicity of the sodium salt is very low. A daily dose of 0.5g, has no toxicity to the body , even in an amount of not more than 4g of health also has no harm. In human and animal tissues it can bind with protein components of the glycine and detoxification, formed hippuric acid excreted in the urine. Benzoic acid crystallites or dust on the skin, eyes, nose, and throat has stimulating effect. Even if its sodium salt, if you take a lot, also can damage to the stomach. The operator should wear protective equipment. Need to be stored in a dry and ventilated place moisture, heat, away from the fire source.

Preparation

Industrial preparation method
The industrial benzoic acid is mainly by toluene liquid phase air oxidation preparation. The process was with cobalt naphthenate as catalyst, in response to temperature is 140-160 ℃ and operating pressure is 0.2-0.3MPa and response generation benzoic acid. Reaction after steaming to toluene, and vacuum distillation and recrystallization to obtain the product. The process uses cheap raw materials, high yield. Therefore, it is industrial uses mainly the method.
Laboratory preparation method of the main reaction:
1.C6H5CH3+ KMnO4+H2O-C6H5 COOK+KOH+MnO2+H2O(water in fron of the manganese dioxide is supplied with water reaction environment)
2.C6H5 COOK+HCl--C6H5 COOH
Drug and dosage:
Toluene 1.5g (1.7ml, 0.016mol), potassium permanganate 5g (0.032mol), CTAB(cetyl trimethyl ammonium bromide) 0.1g.
Experimental operation:
With 100 ml round bottom flask. Install a refluxing device. add 5g potassium permanganate, 0.1g of hexadecyl trimethyl ammonium bromide, 1.7 ml of toluene and 50 ml of water to the reaction flask, stir heated boiling (vigorous stirring, violent boiling), keep the reactant solution stable boiling.
When large amounts of brown precipitate, potassium permanganate purple shallow or disappeared, the toluene layer disappeared, reaction has basically ended. Filter out of manganese dioxide precipitation, landfill leachate by concentrated hydrochloric acid, precipitation of benzoic acid precipitation, filtering to the crude product.
The crude product water recrystallization. In a boiling water bath for drying, weighing, measuring the melting point.

Description

Benzoic acid is a colorless, crystalline solid also known as benzenecarboxylic acid. It is the simplest aromatic carboxylic acid, with a carboxyl group (-COOH) bonded directly to the benzene ring. It is found naturally in the benzoin resin of a number of plants.

Chemical Properties

Benzoic acid,C6H5COOH, also known as benzene carboxylic acid and phenyl formic acid,is a colorless, monoclinic crystalline solid that has a melting point of 122.4"C and sublimes readily at 100·C. It is an aromatic carboxylic acid that is slightly soluble in water and moderately soluble in alcohol and ether. It is used as a preservative and its derivatives are valuable in medicine, commerce, and industry.

Physical properties

Colorless to white needles, scales, or powder with a faint benzoin or benzaldehyde-like odor. Shaw et al. (1970) reported a taste threshold in water of 85 ppm.

Occurrence

Reported found in fresh apple, apricot (Prunus armeniaca L.), strawberry fruit, cherry (Prunus cerasus L.), butter, boiled and cooked beef, pork fat, white wine, black tea, green tea, fresh plum, mushroom, Bourbon vanilla (Vanilla planifolia Andrews), and other natural sources. Reported as being a constituent of various oils, resins and flower absolutes; hyacinth, tuberose, neroli bigarade, Chinese cinnamon, cinnamon leaves, anise, vertiver, ylang-ylang, Tolu balsam and clove; it is contained in fairly sizable amounts in gum benzoin, from which benzoic acid is extracted by sublimation.

History

Benzoic acid was first isolated from the dry distillation of benzoin by Blaise de Vigenère (1523–1596) in the 16th century. Friedrich W?hler (1800–1882) and Justus von Liebig (1803–1873) prepared benzoic acid from oxidizing bitter almond oil (benzaldehyde) in 1832 and determined the formula for each of these compounds. They proposed that bitter almond oil, C₇H₆O, and benzoic acid were derivatives from the benzoyl radical, C₇H₅O; the radical theory was a major early theory in the development of organic chemistry.

Uses

Calorimetry
Benzoic acid is the most commonly used chemical standard to determine the heat of capacity of a bomb calorimeter.
Feed stock
Benzoic acid is used to make a large number of chemicals, important examples of which are :
Benzoyl chloride, C₆H₅C(O)Cl, is obtained by treatment of benzoic with thionyl chloride, phosgene or one of the chlorides of phosphorus. C₆H₅C(O) Cl is an important starting material for several benzoic acid derivates like benzyl benzoate, which is used in artificial flavours and insect repellents.
Food preservative
Benzoic acid and its salts are used as a food preservatives, represented by the E-numbers E210 , E211 , E212 , and E213 . Benzoic acid inhibits the growth of mold, yeast and some bacteria. It is either added directly or created from reactions with its sodium, potassium, or calcium salt. The mechanism starts with the absorption of benzoic acid in to the cell.
Medicinal
Benzoic acid is a constituent of Whitfiel's ointment which is used for the treatment of fungal skin diseases such as tinea, ringworm, and athlete's foot. As the principal component of benzoin resin, benzoic acid is also a major ingredient in both tincture of benzoin and Fria's balsam. Such products have a long history of use as topical antiseptics and inhalant decongestants.
Benzoic acid was used as an expectorant, analgesic, and antiseptic in the early 20th century.

Uses

Sodium benzoate is an important benzoic acid derivative produced industrially by neutralization of benzoic acid using sodium hydroxide or sodium bicarbonate solution. Calcium benzoate, potassium benzoate, and other benzoate salts are also produced. Benzoic acid and sodium benzoate (C₆H₅COONa) are used as food preservatives and added to foods, juices, and beverages that are acidic.

Production Methods

Industrial preparations
Benzoic acid is produced commercially by partial oxidation of toluene with oxygen. The process is catalyzed by cobalt or manganese naphthenates. The process uses cheap raw materials, proceeds in high yield, and is considered environmentally green.
Laboratory synthesis
Benzoic acid is cheap and readily available, so the laboratory synthesis of benzoic acid is mainly practiced for its pedagogical value. It is a common undergraduate preparation.
For all syntheses, benzoic acid can be purified by recrystallization from water because of its high solubility in hot water and poor solubility in cold water. The avoidance of organic solvents for the recrystallization makes this experiment particularly safe. Other possible recrystallization solvents include acetic acid (anhydrous or aqueous), benzene, acetone, petroleum ether, and a mixture of ethanol and water. The solubility of benzoic acid in over 40 solvents with references to original sources can be found as part of the Open Notebook Science Challenge.

Preparation

By oxidation of toluene with nitric acid or sodium bichromate or from benzonitrile.

Definition

ChEBI: A compound comprising a benzene ring core carrying a carboxylic acid substituent.

Reactions

Reactions of benzoic acid can occur at either the aromatic ring or the carboxyl group :
Aromatic ring
Electrophilic aromatic substitution reaction will take place mainly in 3- position due to the electron-withdrawing carboxylic group; i.e. benzoic acid is meta directing.
The second substitution reaction (on the right) is slower because the first nitro group is deactivating. Conversely, if an activating group (electron - donating) was introduced (e.g., alkyl), a second substitution reaction would occur more readily than the first and the disubstituted product might accumulate to a significant extent.
Carboxyl group
All the reactions mentioned for carboxylic acids are also possible for benzoic acid.
Benzoic acid esters are the product of the acid catalysed reaction with alcohols. Benzoic acid amides are more easily available by using activated acid derivatives (such as benzoyl chloride) or by coupling reagents used in peptide synthesis like DCC and DMAP.
The more active benzoic anhydride is formed by dehydration using acetic anhydride or phosphorus pentoxide.
Highly reactive acid derivatives such as acid halides are easily obtained by mixing with halogenation agents like phosphorus chlorides or thionyl chloride.
Ortho esters can be obtained by the reaction of alcohols under acidic water free conditions with benzonitrile.
Reduction to benzaldehyde and benzyl alcohol is possible using DIBAL- H , Li Al H₄ or sodium boro hydride.
The copper catalyzed decarboxylation of benzoate to benzene may be effected by heating in quinoline. Also, Hunsdiecker decarboxylation can be achieved by forming the silver salt and heating. Benzoic acid can also be decarboxylated by heating with an alkali hydroxide or calcium hydroxide.

Biotechnological Production

Benzoic acid is exclusively chemically synthesized on an industrial scale. Toluene from petrochemical routes is oxidized in the presence of the catalyst potassium permanganate to benzoic acid . However, a recent study described for the first time a benzoic acid production process by fermentation using Streptomyces maritimus. The production of benzoic acid during cultivation on glucose, starch, and cellobiose has been investigated. The best results have been achieved with product concentrations of 460 mg.L-1 in 6 days using starch as substrate. Additionally, a genetically modified S. maritimus optimized for endo-glucanasesecretion has been tested on phosphoric acid swollen cellulose. A final product concentration of 125 mg.L-1 was observed after 4 days of cultivation.

Aroma threshold values

85 ppm.

Synthesis Reference(s)

Canadian Journal of Chemistry, 50, p. 3741, 1972 DOI: 10.1139/v72-592
Chemistry Letters, 5, p. 147, 1976
Tetrahedron Letters, 23, p. 2347, 1982 DOI: 10.1016/S0040-4039(00)87338-4

General Description

Boric acid,H3B03, also known as boracic acid, orthoboric acid, and sassolite, is a white solid composed of triclinic crystals.It is a derivative of barium oxide and is soluble in water. A white crystalline solid. Slightly soluble in water. The primary hazard is the potential for environmental damage if released. Immediate steps should be taken to limit spread to the environment. Used to make other chemicals, as a food preservative, and for other uses.

Air & Water Reactions

Vapor from molten Benzoic acid may form explosive mixture with air. The finely powdered dry acid is a significant dust explosion hazard [Bretherick, 5th ed., 1995, p. 884]. In air very rapid combustion occurs [Wilson, L.Y. et al., J. Chem. Ed., 1985, 62(10), p. 902]. Slightly soluble in water.

Reactivity Profile

At high temperature Benzoic acid can react with oxidizing reagents.

Hazard

Moderately toxic by ingestion. Use restricted to 0.1% in foods.

Health Hazard

Dust may be irritating to nose and eyes. At elevated temperatures, fumes may cause irritation of eyes, respiratory system, and skin.

Fire Hazard

Behavior in Fire: Vapor from molten Benzoic acid may form explosive mixture with air. Concentrated dust may form explosive mixture.

Agricultural Uses

Fungicide, Insecticide: Used in the manufacture of benzoates; plasticizers, benzoyl chloride, alkyd resins, in the manufacture of food preservatives, in use as a dye binder in calico printing; in curing of tobacco, flavors, perfumes, dentifrices, standard in analytical chemistry. Not currently registered for use in the U.S. Benzoic acid is currently used in about a dozen European countries.

Pharmaceutical Applications

Benzoic acid is widely used in cosmetics, foods, and pharmaceuticals, as an antimicrobial preservative. Greatest activity is seen at pH values between 2.5–4.5.
Benzoic acid also has a long history of use as an antifungal agent in topical therapeutic preparations such as Whitfield’s ointment (benzoic acid 6% and salicylic acid 3%).

Trade name

RETARDER BA®; MICROL® Preservative; TENN-PLAS®; RETARDEX®; SALVO LIQUID®; SALVO POWDER®; TULSA®

Clinical Use

Benzoic acid is a metabolite of benzyl alcohol and sodium benzoate is the sodium salt of benzoic acid. These three related compounds are used as preservatives in a variety of products, such as cosmetics, toothpastes, hair products, medication preparations, and emollients, and in foods. They are well-recognized to cause nonimmunological CoU and reactions are concentration-dependent.Both oral intake and cutaneous contact of benzyl alcohol, benzoic acid, or sodium benzoate can cause immediate reactions; however, there is a lack of correlation between the two and skin tests should not be used to predict sensitivity to oral intake of these preservatives.
Immediate reactions to the oral ingestion of these preservatives are rare. Nettis et al. investigated 47 patients with a history of urticaria after the ingestion of meals or products containing sodium benzoate, and only one patient had a generalized urticarial reaction to an oral challenge test of 50 mg of sodium benzoate.

Side effects

Benzoic acid occurs naturally free and bound as benzoic acid esters in many plant and animal species. Appreciable amounts have been found in most berries (around 0.05 %). Ripe fruits of several Vaccinium species (e.g., cranberry, V. vitis idaea; bilberry, V. macrocarpon) contain as much as 0.03 – 0.13 % free benzoic acid. Benzoic acid is also formed in apples after infection with the fungus Nectria galligena. Among animals, benzoic acid has been identified primarily in omnivorous or phytophageous species, e.g., in viscera and muscles of the Rock Ptarmigan (Lagopus muta) as well as in gland secretions of male muskoxen (Ovibos moschatus) or Asian bull elephants (Elephas maximus).
Gum benzoin contains up to 20 % of benzoic acid and 40% benzoic acid esters.

Toxicology

Four-generation reproductive and developmental toxicities of benzoic acid were examined using diets containing 0, 0.5, and 1% of benzoic acid fed to male and female rats housed together for eight weeks. The second generation was observed through its entire life cycle and the third and fourth generations were examined by autopsy. No changes in normal patterns of growth, reproduction, or lactation during life were recorded and no morphological abnormalities were observed from the autopsies.
Degradation pathways for benzoic acid also have been studied in detail and the results have supported the harmlessness of this substance. The total dose of benzoic acid is excreted within 10 to 14 hours and 75 to 80% is excreted within 6 hours. After conjugation with glycine, 90% of benzoic acid appears in the urine as hippuric acid. The rest forms a glucuronide,1-benzoylglucuronic acid. The lower aliphatic esters of benzoic acid are first hydrolyzed by esterase, which abounds in the intestinal wall and liver. The resulting benzoic acid subsequently is degraded in the usual manner.

Safety

Ingested benzoic acid is conjugated with glycine in the liver to yield hippuric acid, which is then excreted in the urine; care should be taken when administering benzoic acid to patients with chronic liver disease. Benzoic acid is a gastric irritant, and a mild irritant to the skin. It is also a mild irritant to the eyes and mucous membranes. Allergic reactions to benzoic acid have been reported, although a controlled study indicated that the incidence of urticaria in patients given benzoic acid is no greater than in those given a lactose placebo. It has been reported that asthmatics may become adversely affected by benzoic acid contained in some antiasthma drugs.
The WHO acceptable daily intake of benzoic acid and other benzoates, calculated as benzoic acid, has been set at up to 5 mg/kg body-weight. The minimum lethal human oral dose of benzoic acid is 500 mg/kg body-weight.
LD₅₀ (cat, oral): 2 g/kg
LD₅₀ (dog, oral): 2 g/kg
LD₅₀ (mouse, IP): 1.46 g/kg
LD₅₀ (mouse, oral): 1.94 g/kg
LD₅₀ (rat, oral): 1.7 g/kg

Potential Exposure

Benzoic acid is used in production of plasticizers, benzoyl chloride, sodium benzoate and alkyl resins; in the manufacture of benzoates; in the manufacture of food preservatives; as a dye binder in calico printing; in curing of tobacco, flavors, perfumes, dentifrices; standard in analytical chemistry; antifungal agent.

target

ATP

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately.If this chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.

Carcinogenicity

Benzoic acid was not genotoxic in bacterial assays or in in vitro mammalian assays.

Source

Naturally occurs in cranberries, ligonberries (1,360 ppm), peppermint leaves (20–200 ppb), tea leaves, cassia bark, carob, blessed thistle, purple foxglove, jasmine, hyacinth, apples, tobacco leaves, daffodils, autumn crocus, prunes, anise seeds, ripe cloves, and wild black cherry tree bark (Duke, 1992; quoted, Verschueren, 1983).
Schauer et al. (1999) reported benzoic acid in diesel fuel at a concentration of 1,260 μg/g. Identified as an oxidative degradation product in the headspace of a used engine oil (10–30W) after 4,080 miles (Levermore et al., 2001).
The gas-phase tailpipe emission rate from California Phase II reformulated gasoline-powered automobile equipped with a catalytic converter was 124 μg/km (Schauer et al., 2002). Benzoic acid is a by-product of benzoyl peroxide used in the bleaching of freshly milled wheat flour. A maximum benzoic acid concentration of 16 ppm was reported after 12 h of bleaching. The concentration decreased to 6 ppm after 3 months (Saiz et al., 2001).
A liquid swine manure sample collected from a waste storage basin contained benzoic acid at a concentration of 4.0 mg/L (Zahn et al., 1997).

Environmental Fate

Biological. Benzoic acid may degrade to catechol if it is the central metabolite whereas, if protocatechuic acid (3,4-dihydroxybenzoic acid) is the central metabolite, the precursor is 3- hydroxybenzoic acid (Chapman, 1972). Other compounds identified following degradation of benzoic acid to catechol include cis,cis-muconic acid, (+)-muconolactone, 3-oxoadipate enol lactone, and 3-oxoadipate (quoted, Verschueren, 1983). Pure microbial cultures hydroxylated benzoic acid to 3,4-dihydroxybenzoic acid, 2- and 4-hydroxybenzoic acid (Smith and Rosazza, 1974). In activated sludge, 65.5% mineralized to carbon dioxide after 5 d (Freitag et al., 1985). Photolytic. Titanium dioxide suspended in an aqueous solution and irradiated with UV light (λ = 365 nm) converted benzoic acid to carbon dioxide at a significant rate (Matthews, 1986). An aqueous solution containing chlorine and irradiated with UV light (λ = 350 nm) converted benzoic acid to salicylaldehyde and unidentified chlorinated compounds (Oliver and Carey, 1977). A carbon dioxide yield of 10.2% was achieved when benzoic acid adsorbed on silica gel was irradiated with light (λ >290 nm) for 17 h (Freitag et al., 1985).
Brubaker and Hites (1998) measured the OH radical rate constant for benzoic acid between 333 and 363 K. The rate constants (x 1012 cm³/sec) were 0.42 and 0.66 at 333 K (two determinations), 0.84 at 343 K, and 0.72 at 363 K. In water, benzoic acid reacted with OH radicals at a rate of 1.2 x 1013/M·h at 25 °C (Armbrust, 2000).
Chemical/Physical. At an influent concentration of 1.0 g/L, treatment with GAC resulted in an effluent concentration of 89 mg/L. The adsorbability of the carbon used was 183 mg/g carbon (Guisti et al., 1974). Ward and Getzen (1970) investigated the adsorption of aromatic acids on activated carbon under acidic, neutral, and alkaline conditions. The amount of benzoic acid (10-4 M) adsorbed by carbon at pH values of 3.0, 7.0, and 11.0 were 49.7, 11.2, and 2.5%, respectively. Similarly, at influent concentrations of 1.0, 0.1, 0.01, and 0.001 mg/L, the respective GAC adsorption capacities were 130, 51, 19, and 7.3 mg/g at pH 3.0 and 54, 0.76, 0.01, and 0.002 mg/g at pH 7.0 At pH 9.0 and influent concentrations of 10 and 1.0 mg/L, the GAC adsorption capacities were 21 and 0.008, respectively (Dobbs and Cohen, 1980).

storage

Aqueous solutions of benzoic acid may be sterilized by autoclaving or by filtration.
A 0.1% w/v aqueous solution of benzoic acid has been reported to be stable for at least 8 weeks when stored in polyvinyl chloride bottles, at room temperature.
When added to a suspension, benzoic acid dissociates, with the benzoate anion adsorbing onto the suspended drug particles. This adsorption alters the charge at the surface of the particles, which may in turn affect the physical stability of the suspension. The addition of sodium azide has been shown to increase the stability of benzoic acid in skin permeation experiments.
The bulk material should be stored in a well-closed container in a cool, dry place.

Shipping

UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9—Miscellaneous hazardous material, Technical Name Required.

Purification Methods

For use as a volumetric standard, analytical reagent grade benzoic acid should be carefully fused to ca 130o (to dry it) in a platinum crucible, and then powdered in an agate mortar. Benzoic acid has been crystallised from boiling water (charcoal), aqueous acetic acid, glacial acetic acid, *C6H6, aqueous EtOH, pet ether (b 60-80o), and from EtOH solution by adding water. It is readily purified by fractional crystallisation from its melt and by sublimation in a vacuum at 80o. The S-benzylisothiuronium salt has m 167o (from EtOH/H2O). [Beilstein 9 IV 273.]

Incompatibilities

Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides, caustics, ammonia, amines, isocyanates. Dust forms an explosive mixture with air.

Waste Disposal

Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. All federal, state, and local environmental regulations must be observed.

Regulatory Status

GRAS listed. Accepted as a food additive in Europe. Included in the FDA Inactive Ingredients Database (IM and IV injections, irrigation solutions, oral solutions, suspensions, syrups and tablets, rectal, topical, and vaginal preparations). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.