Sodium chlorite decomposition

Sodium Chlorite. The standard enthalpy, Gibbs free energy of formation, and standard entropy for aqueous chlorite ions ate AH° = —66.5 kJ/mol ( — 15.9 kcal/mol), AG = 17.2 kJ/mol (4.1 kcal/mol), and S° = 0.1883 kJ/(molK) (0.045 kcal/(molK)), respectively (107). The thermal decomposition products of NaClO, in the 175—200°C temperature range ate sodium chlorate and sodium chloride (102,109) ... 

Many of the metal chlorites are not particularly stable and will explode or detonate when stmck or heated. These include the salts of Hg", Tl", Pb ", Cu", and Ag". Extremely fast decomposition with high heat evolution has been noted for barium chlorite [14674-74-9] Ba(Cl02)2, at 190°C, silver chlorite [7783-91-7] AgC102, at 120°C, and lead chlorite [13453-57-17, at 103°C (109). Sodium chlorite can be oxidized by ozone to form chlorine dioxide under acidic conditions (110) ... 

The sodium chlorite/sodium hydrosulphite mixture combusts spontaneously. This is explained by the fact that sulphur-containing salts catalyse the decomposition of chlorite. 

Figure 10.34 Decomposition of sodium chlorite solution as a function of pH [235]...

Use of a scoop contaminated with sodium dithionite for sodium chlorite caused ignition of the latter. Materials containing sulfur (dithionite, natural rubber gloves) cause decomposition of sodium chlorite and contact should be avoided. 

K. G. Thurnlackh and K. F. von Hayn prepared a mixed soln. of potassium chlorate and chlorite by the action of potassium hydroxide free from chlorine on a soln. of chlorine dioxide. Light was carefully excluded, and the soln. was evaporated in vacuo at 45°-50°—potassium chlorate separated out first, and after further evaporation, alcohol was added, and the clear alcoholic soln. evaporated. Needle-like crystals of potassium chlorite, KC102, were obtained which deliquesced on exposure to air. As already indicated in connection with the preparation of the acid, G. Bruni and G. Levi made the potassium chlorite by reducing a soln. of potassium chlorate with oxalic acid and A. Reychler, sodium chlorite, by the action of chlorine dioxide on a soln. of sodium peroxide. Sodium chlorite, NaClQ2, can be also made by double decomposition by treating a soln. of barium chlorite with sodium sulphate and evaporating the clear soln. in vacuo. 

Oxidants. Violent decomposition can occur in the presence of oxidants.4 Sodium Chlorite. Mixture ignites.5... 

Sodium chlorite is manufactured on a ton scale for use as a bleaching agent. In alkaline solution the ion is stable to prolonged boiling and up to a year at 25°C in the absence of light. In acid solutions, however, the decomposition is rapid and is catalyzed by Cl ... 

Evaporation of sodium chlorite solutions may lead to loss of chlorite through decomposition and this has been examined . Two parallel reactions... 

N. A, E. Millon prepared soln. of potassium chlorite and sodium chlorite by adding chlorous acid slowly and gradually to a soln. of the alkali hydroxide until the product has a yellow colour. By rapidly evaporating the soln. to complete dryness, a deliquescent salt was obtained which, at 160°, decomposes into chlorate and chloride. This decomposition occurs if the soln. be slowly evaporated in vacuo. If an excess of chlorous acid is used with the pot ash-lye, a red liquid is obtained which gives off the acid on evaporation, and leaves a residue of the neutral salt. It has been suggested that the red liquid is a soln. of add potassium chlorite. 

Due to its easily initiated self-decomposition, solid sodium chlorite is either supplied as its monohydrate or as mixtures with sodium chloride or sodium nitrate. 

AMMONIUM OXALATE, ANHYDROUS (1113-38-8) CjHsNj04 (Fire Rating 1). Incompatible with acids, ammonium acetate furfliryl alcohol, silver, sodium chlorite, sodium hypochlorite oxidizers. Attacks many metals. Heat of decomposition or fire produces fumes of ammonia, nitrogen oxides, carbon monoxide, carbon dioxide, formic acid. Attacks steel. On small fires, use foam, dry powder, water, or CO2 extinguishers. 

OXALIC ACID (144-62-7) CjHjO. HOOCCOOH Combustible solid heat-sensitive. (combustible <215 F/101°C. Fire Rating 1). Exposure to elevated temperatures, hot surfaces, or flames causes decomposition and the formation of toxic and flammable formic acid and carbon monoxide. Hygroscopic the solution in water is a medium-strong acid. Violent reaction with strong oxidizers, acid chlorides alkali metals bromine, furfuryl alcohol hydrogen peroxide (90%) phosphorus trichloride silver powders sodium, sodium chlorite sodium hypochlorite urea + heat (forms NHj gas, CO2 and CO may explode). Mixture with some silver compounds forms explosive salts of silver oxalate. Incompatible with caustics, mercury, urea. On small fires, use dry chemical powder (such as Purple-K-... 

HYDROLIN (7775-14-6) Combustible solid. Finely dispersed dust or powder forms explosive mixture with air. Contact with water, moist air, or steam, emitting sulfur dioxide and heat, with risk of spontaneous combustion. Contact with acids produces sulfur dioxide. A strong reducing agent. Violent reaction, ignition, or explosion on contact with oxidizers, sodium chlorite. Elevated temperatures above 122°F/50°C may cause violent thermal decomposition, producing sodium sulfate and sulfur dioxide. When dissolving, always slowly add this material to water. 

EXPLOSION and FIRE CONCERNS NFPA rating (not available) reacts violently with oxygen at 300 C violent reaction with sodium reacts explosively with trialkylphosphines and silver chlorite decomposition emits toxic fumes of F use water spray, carbon dioxide, dry chemical powder, or appropriate foam for firefighting purposes. 

Mildly alkaline solutions of sodium chlorite are stable for periods up to a year, and even with prolonged boiling no decomposition occurs if light is excluded (24, 25, 59, 97, 220). In hot, strongly alkaline solution, chlorine dioxide is not formed but chlorate ion is the principal product of the decomposition (22, 193, 226). 

As the pH is lowered, a chlorite ion solution becomes less stable. Neutral solutions of sodium chlorite are reasonably stable if they are kept away from light and heat, but a solution will decompose slowly if heated (22, 97, 162, 220). As in the case of the alkaline solution, the decomposition of a neutral solution of the chlorite produces no chlorine dioxide only chlorate ion and chloride ion are formed (8, 28, 220, 226). 

It was reported that the decomposition by 5.5M HOI is nearly complete and that chlorine and not chlorine dioxide is produced. By contrast, Kepinski and Blaszkiewicz (118) indicated that with O.lW Na0102 and 5.0W HOl the decomposition of chlorine(III) is complete within 1 min, but no chlorine is detected. Beuermann (14) found that only small amounts (ca. 2%) of chlorine were produced when hydrochloric acid reacted with sodium chlorite. Although chlorine has been reported among the reaction products (10, 18, 75, 76, 118), the bulk of evidence appears to be against the formation of any chlorine (91, 99, 120, 162, 217,... 

The rate of disproportionation of acidified chlorine (III) solutions varies with the pH. The reaction is very slow at a pH greater than 4 less than 10 W chlorine dioxide is formed in 2 hr if the initial sodium chlorite concentration (28) is 3 x 10 Only if the pH is less than 3 will more than 1% of the sodium chlorite decompose within 10 min. Kieffer and Gordon (120) found that the rate of decomposition of chlorous acid did not vary appreciably with hydrogen ion concentration in the 2.0 to 0.2M range in the absence of initial chloride ion. The half-life for the decoitpos-ition was approximately 3 hr for 1.2M hydrogen ion,... 

X 10"% sodium chlorite, 2.0W ionic strength, at 25°C. The rate was about three times faster at 3.33 x 10"% hydrogen ion concentration. Hefti (92) studied the decomposition of a sodium chlorite solution in an acetic acid sodiiam acetate buffer. At 95°C with 0.2W buffer, the decomposition reaction was slow at pH 5 to 7, but below pH 5 the reaction was fast. 

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