Chemistry Reference
In-Depth Information
8.7.2
Paper chromatography
Thieleman [23] attempted the separations of cyanate, thiocyanate and cyanide ions by
thin-layer and paper chromatography.
The three ions were successfully separated by paper chromatography using
methanol:pyridine:dioxan (7:2:1) as solvent in 8h.
Cyanate was identified using a bromocresol purple spray reagent. Carbonate ions
interfered.
Cyanate and cyanide in waste water have also been separated by paper
chromatography [24]. Separation was achieved by the use of isopropyl
alcohol:ethanol:water (9:4:3) as solvent with Filtrak FN8 paper. Bromo-cresol green
solution was used as spray reagent which produced clear green spots on a blue
background with cyanate and cyanide.
8.7.3
Miscellaneous
See section 14.12.5.1.
8.8
Cyanide (free)
8.8.1
Titration method
Workers at Orion Research Inc. US [25] have described a method for the determination
of free cyanide in wastewaters from a cyanide extraction process of gold by a first
derivative titration technique using an Orion 960 autochemistry system, equipped with an
Orion silver/sulphide electrode and Orion Sure-Flow Reference electrode. One mL of
10N sodium hydroxide is added to 50ml of sample and titration is carried out using 0.1N
silver nitrate to the single end-point indicated on an automatic recorder. Chloride,
thiocyanate and thiosulphate have no effect on cyanide determination. Sulphide when
present will cause two end points, the first for sulphide and the second for cyanide.
8.8.2
Spectrophotometric method
Fu-Sheng
et al.
[26] applied the copper-cadion 2B-Trition A-100 system to the
Spectrophotometric determination of micro accounts of free cyanide in waste water.
Nagashima and Ozawa [27] have given details for the determination of cyanide in
aqueous samples by spectrophotometry, using isonicotinic acid and barbituric acid as
reagents. Cyanide reacts with chloramine-T, and then the reagent is added to form a
soluble violet-blue product, which is measured at 600nm. Maximum absorbance is
achieved in 15min at 25°C and remains constant for about 30min. This method is
applicable to water samples containing 0-5mg L
−1
cyanide. Results obtained on several
plating waste waters are reported and show good agreement with those obtained by the
conventional pyridine-pyrazolone method [28].
Details of the isonicotinic acid-barbituric acid procedure are given below.
Search WWH ::
Custom Search