Hydrocyanic acid analysis

The methods of analysis are those used for other spirits in addition, for nut-fruit spirits, hydrocyanic acid and benzaldehyde and sometimes nitrobenzene are tested for and determined as follows ... 

With his colleague Louis-Jacques Thenard (1777-1857), Gay-Lussac did considerable work with electrochemistry to produce significant amounts of elemental sodium and potassium, highly reactive and useful substances that were used to isolate and discover the element boron. Gay-Lussac also completed extensive studies of acids and bases and was the first to deduce that there were binary (two element) acids such as hydrochloric acid (HC1) in addition to the known oxygen-containing acids like sulfuric acid (H2S04). Additionally, he was able to determine the chemical composition of prussic acid to be hydrocyanic acid (HCN) and was considered the foremost practitioner of organic analysis. 

Several analytical procedures have been based on this reaction, e.g., those of Seil, Page, etc. The following is especially suitable for the analysis of hydrocyanic acid used in the mixtures of gases used for disinfestation. 

This pyrolysis technique was used in the analysis of copolymers of acrylonitrile with styrene in a broad range of monomer ratio variations [34]. An ampoule containing a weighed amount (5—10 mg) of the polymer was pre-evacuated down to a residual pressure of 10" mmHg. The pyrolysis was conducted for 20—30 min at 500°C. The composition of the copolymers can be determined from the peaks of hydrocyanic acid and toluene, which are present in the pyrolysis products in amounts proportional to those of acrylonitrile and toluene, respectively, initially present in the copolymer. 

Note that direct elution analysis of carbon dioxide even in large samples (25 ml) fails to determine trace hydrocarbons without concentration. The method may be recommended for the trace analysis of other acid gases (e.g., hydrogen sulphide, hydrocyanic acid). A chemical concentration method based on removal of unsaturated gaseous hydrocarbons (main component) for determination of trace amounts of hydrogen and carbon dioxide was developed by Alekseeva and co-workers [56, 57]. For absorption of olefins use was made of a column containing a solution of silver nitrate and mercury salts. 

Notwithstanding the volatility and instability of the poison, its presence has been detected two months after death, although the chances of separating it are certainly the better the sooner after death the analysis is made. The search for hydrocyanic acid is combined with that for phosphorus the part of the distillate containing the more volatile products is examined by the tests given above. It is best, when the presence of free hydrocyanic acid is suspected, to distil at first without acidulating. In cases of suspected homicide by hydrocyanic acid the stomach should never be opened until immediately before the analysis. 

It can be assumed that the samples received for analysis from water supply authorities will mostly be free of sulphide and thiocyanate and will not contain any oxidizing agents which would interfere with the analysis. However, with chlorinated or otherwise partly contaminated water, an excess of oxidizing agents is to be expected. Samples taken from this latter type of water must have an excess of reducing agents added to them immediately after sampling. For this purpose first add 5 ml of 5 m sodium hydroxide for every litre of the water sample (in order to avoid any loss of free hydrocyanic acid) and then 5 ml of an approx. 50 % solution of tin(II)chloride. 

Benzoin had been observed by Robiquet and Boutron-Charlard but was first correctly examined by Wohler and Liebig. They obtained it by the action of alkali on benzaldehyde, and found by analysis that it is isomeric with benzaldehyde (it is C6H5-CH(OH) CO C6H5). Zinin first showed that its formation depends on the presence of hydrocyanic acid in the oil of bitter almonds, and the catalyst for the reaction is potassium cyanide. Benzo-phenone was discovered by Peligot. Benzonitrile, CgHgCN, was discovered... 

M.C. Quaresma, M.F. de Carvalho, F.A. Meirelles, V.M. Santiago, R.E. SanteUi, AppUcation of hydrocyanic acid vapor generation via focused microwave radiation to the preparation of industrial effluent samples prior to free and total cyanide determinations by spectrophotometric flow injection analysis. Anal. Bioanal. Chem. 387 (2007) 1017-1025. 

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