Cyanide distillation method

Separation of Easily Released Cyanide (Distillation Method)... 

The method can be used with all types of water whose content of easily released cyanide does not exceed 50 mg CN"/1, If the cyanide content is higher than this, the water sample must be diluted. The method described for use with "total cyanide" (distillation method) also applies in virtually all respects to the method for separating easily released cyanide. 

Distillation apparatus, flow meter, wash bottle and 25 ml measuring flasks are the same as described in the section "Total Cyanide" (Distillation Method). 

Huang, Q., Pauli, B. Haddad, P.R. (1996) Comparison of cyanide speciation by liquid chromatography and standard distillation methods. Chem. Aust., 63, 310-311. 

The purpose of the distillation method is to release the total cyanide from the water sample under controlled conditions and to convert it into a form in which it can be measured using one of the methods described. This means the total cyanide which occurs in organic and inorganic cyanide compounds or complexes and which can be split up under the same conditions as those prevailing in the environment (temperature up to 30 C, exposure to light, aeration, shift in pH, breakdown by microbes). The differentiation between total cyanide and easily released cyanide ( easily decomposed cyanide ) results from the choice of decomposition conditions in the distillation flask. 

The distillation method of determining total cyanide content is suitable for levels of between 0.02 and 100 mg CN"/1, if 100 ml of water sample is used. If 300 ml sample is used, levels as low as 0.005 mg CN /1 can be detected. If the total cyanide content is around or above 100 mg CN /1, the water sample must be diluted. 

A semiautomatic method was described for the routine determination of cyanide in water [40]. Membrane diffusion and isothermal distillation are examined for the separ-ation/concentration of cyanide. An air-segmented flow analyzer is used to quantify cyanide. The method based on reaction with picric acid is applicable at cyanide concentrations exceeding 1 mg. The method is suitable for the determination of cyanide in waters in the concentration range of 0.01-10 mg... 

Allyl cyanide. Into a 1 5 litre three-necked flask (1), provided with a mercury-sealed stirrer and two long double surface condensers, place 293 g. (210 ml.) of freshly-distilled allyl bromide, b.p. 70-71° (Section III, 35) and 226 g. of dry cuprous cyanide (Section 11,50,3, Method 1), Remove the mercury-sealed stirrer and replace it by a tightly fitting... 

Nitdles may be prepared by several methods (1). The first nitrile to be prepared was propionitdle, which was obtained in 1834 by distilling barium ethyl sulfate with potassium cyanide. This is a general preparation of nitriles from sulfonate salts and is referred to as the Pelou2e reaction (2). Although not commonly practiced today, dehydration of amides has been widely used to produce nitriles and was the first commercial synthesis of a nitrile. The reaction of alkyl hahdes with sodium cyanide to produce nitriles (eq. 1) also is a general reaction with wide appHcabiUty ... 

There is a discrepancy between the cyanide criteria for both aquatic and drinking water standards and the current analytical technology. The criteria are stated for free cyanide (which Includes hydrocyanic acid and the cyanide ion), but the EPA approved analytical methodology for total cyanide measures the free and combined forms (11). This test probably overestimates the potential toxicity. An alternative method (cyanides amenable to chlorination) measures those cyanide complexes which are readily dissociated, but does not measure the iron cyanide complexes which dissociate in sunlight. This method probably tends to underestimate the potential toxicity. Other methods have been proposed, but similar problems exist (12). The Department of Ecology used the EPA-approved APHA procedure which includes a distillation step for the quantification of total cyanide (13,14). A modification of the procedure which omits the distillation step was used for estimation of free cyanide. Later in the study, the Company used a microdiffusion method for free cyanide (15). 

Water (drinking, surface, saline, domestic, and industrial waste) (EPA Method 335.1) Chlorination of sample at pH 11-12 and CICN driven off reflux-distillation of residual sample absorption of released HCN in NaOH treatment with chloramine-T and pyridine-pyrazolone or pyridine-barbituric acid Spectrophotometry (cyanide amenable to chlorination) No data No data EPA 1983a... 

Waste or leachate (EPA Method 901OA) Reflux-distillation of acidified sample absorption of released HCN in NaOH treatment with AgNOs and an indicator (titrimetric) or chloramine-T/pyridine-barbituric acid (colorimetric) Titrimetric or colorimetric detection (total and amenable cyanide) 0.1-0.2 mg/L titrimetric) 0.02 mg/L (colorimetric) (Titrimetric) 94-99 (total cyanide), 87-97 (amenable cyanide) EPA1992d... 

Nitriles can also be obtained by the method of Kolbe alkyl iodides (bromides or chlorides) are heated with alkali cyanide (example, benzyl cyanide), or salts of alkylsulphuric acids are subjected to dry distillation with potassium cyanide ... 

One method of purifying the benzyl cyanide is to steam distil it after the alcohol has been first distilled from the reaction mixture. At ordinary pressures, this steam distillation is very slow and, with an ordinary condenser, requires eighteen to twenty hours in order to remove all of the volatile product from a run of 500 g. of benzyl chloride. The distillate separates into two layers the benzyl cyanide layer is removed and distilled. The product obtained in this way is very pure and contains no tarry material, and, after the excess of benzyl chloride has been removed, boils practically constant. This steam distillation is hardly advisable in the laboratory. 

The FINAL TREATMENT Distillation Unit uses a new method to concentrate the cyanide ions in order to minimize the volume of the waste solution. 

Different types of methods for purification have been applied. Brauner in 1889, by means of aqua regia, converted crude tellurium into telluric chloride, the aqueous solution of which on precipitation by sulphur dioxide deposited the element together with selenium and traces of copper and lead as the only impurities. The precipitate was dissolved in fused potassium cyanide in an atmosphere of hydrogen and the tellurium separated from the aqueous extract by treatment with a current of air. The element was then distilled in a current of hydrogen, 1 an alternative is distillation in a vacuum.5 Another method of treatment for the telluric chloride solution is to precipitate in three fractions using sulphur dioxide, when it is found that the middle fraction is of a high degree of purity.6... 

Method I.—14 gms. (1 mol.) of finely powdered 96% potassium cyanide, and 20 gms. (1 mol.) of freshly distilled benzaldehyde are placed in a flask cooled with ice and salt. The quantity of the most cone, hydrochloric acid available, corresponding to 7 gms. (1 mol.) of anhydrous acid (about 20 gms. cone, acid will be required), are slowly dropped in with frequent shaking. This must be done in a good fume cupboard. The whole is allowed to stand for 1 hour, being shaken at frequent intervals it is then poured into 5 volumes of water, and the oil which separates well washed with water several times a further purification is impossible owing to its instability. 

Volhard s Method.—39 gms. potassium cyanide and 10 gms. caustic potash are dissolved in 100 c.cs. of water in a large flask. 63 gms. potassium permanganate dissolved in 1 litre of water are then added, drop by drop, from a funnel, the flask being placed in a freezing mixture. The temperature should not rise above 8°. This is filtered, and a solution of 80 gms. ammonium sulphate is added, and the whole evaporated to dryness, The residue is powdered and extracted with 80 c.cs. absolute alcohol under a reflux at boiling point for hour. It is then filtered and the residue washed with boiling alcohol. The alcohol is removed by distillation until the volume is about 50 c.cs. It is then placed in a glass dish and allowed to stand. The crystals which separate are filtered, washed with alcohol, and dried. A second crop of crystals can be obtained from the mother liquor. 

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