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Cyanide (Free) Test Kits

Visual Kit

Range MDL Method Type Kit Cat. No. Refill
0.00 - 0.10 & 0.1 - 1.0 ppm 0.005 ppm Isonicotinic-Barbituric Acid CHEMets K-3810 R-3810

Instrumental Kit

Range Method Type Kit Cat. No.
0 - 0.400 ppm Isonicotinic-Barbituric Acid Vacu-vials K-3803

CHEMetrics offers test kits employing the well-known Isonicotinic-Barbituric Acid reagent to deliver sensitivity and accuracy within two minutes or less. Based on CHEMetrics patented Self-Filling Reagent Ampoule technology. Premixed. Premeasured. Precise. Each kit contains 30 tests.

The Isonicotinic-Barbituric Acid Method

In the Cyanide CHEMets® and Vacu-vials® Kit, chlorine is added to a sample that has been buffered to pH 6. The resulting cyanogen chloride reacts with isonicotinic and barbituric acids to form a blue colour. Results are expressed as ppm (mg/l) CN.

This chemistry provides two advantages over the more commonly used Pyridine methods:

  • The shelf life of the reagent is extended
  • The analyst is not exposed to noxious and hazardous Pyridine fumes

S. Nagashima, Spectrophotometric Determination of Cyanide with Isonicotinic Acid and Barbituric Acid, International Journal of Environ. Anal. Chem., 1981, Vol. 10, pp. 99-106.

Technical Data Sheet


Cyanide is used in many chemical and refining processes. It is found in effluent from electroplating and metal cleaning operations, coke ovens, steel manufacturing facilities, gas scrubbers and polymer production. Low levels may occur naturally in groundwaters after it has passed through mineral deposits and rock strata.

Cyanide can be safely removed from water by alkaline chlorination. However, due to its acute toxicity to aquatic life, discharges from industrial and municipal wastewater facilities are regulated through permitting processes, necessitating routine effluent monitoring. It is common to monitor effluents and surface water supplies for cyanide to ensure that it is not entering natural waters or potential drinking water sources.

Due to the potential for both short-term and long-term health effects to humans, levels are tightly controlled. The Directive Prescribed Concentration or Value (PCV) for free cyanide in drinking water in the UK and Ireland is 50 µg/l (ppb). The Maximum Contaminant Level (MCL) for free cyanide in drinking water set by the USEPA is 200 µg/l.

CHEMetrics free cyanide water test kits are applicable for monitoring effluents and surface water supplies. Sample pretreatment to remove hydrogen sulfide is recommended. For total cyanide analysis, distillation of the sample is required. See the test instructions in the table above for more information.

What is Cyanide?

Cyanide (CN) is a chemical compound known as a cyano group, with a carbon-nitrogen triple bond. In ionic form, it readily reacts with transition metals which makes it useful for chemical and refining processes but also makes it a toxic compound. Inorganic cyanides, such as NaCN or KCN, contain the highly toxic CN- anion. In organic cyanides, the cyano group is linked to the carbon atom though a single covalent bond. Nitriles, with the chemical formula R-CN, do not release CN- ions, whereas cyanohydrins, which have CN- and OH- groups attached to a carbon atom, do. Free cyanide is defined as the sum of molecular hydrogen cyanide (HCN) and cyanide ion (CN). Total cyanide is the sum of all inorganic forms of cyanide that dissociate into free cyanide when refluxed under strongly acidic conditions.