Cyanide absorption

The increased hydrogen cyanide absorption caused by the addition of moisture was only slightly perceptible in the analytical results, since the samples were all very moist anyway, and because the material dried out during the final storage phase and therefore the hydrogen cyanide was only able to bind partially. 

When the irradiation is cut off, the cyanide absorption band disappears, showing that recombination of CN" takes place the Fe(CN)5(OH) " ions are slowly converted back to Fe(CN) " ions. The kinetics related to the absorption band of the Fe(CN)5(OH) "... 

The results obtained with other a-halonitriles are indicated in Table VII. With the exception of chlorodiphenylacetonitrile, PMR spectra of the resulting complexes indicated attachment of the cobalt atom alpha to the nitrile group. In the case of chlorodiphenylacetonitrile (in 25 ml. benzene), the benzene layer was separated from the yellow-aqueous layer after 1 hour reaction time. Adding ethanol to the benzene solution yielded tetraphenylsuccinonitrile, m.p. 203-4°C. (acetic acid) (205°C. reported) (49), The aqueous layer was worked up in the usual manner to obtain a white solid, exhibiting a single cyanide absorption band at 2130 cm." and a carbonyl absorption at 1575 cm.. The PMR spectrum showed aromatic and aliphatic protons in the ratio 10 1. 

Some birds may not die immediately after drinking lethal cyanide solutions. Sodium cyanide rapidly forms free cyanide in the avian digestive tract (pH 1.3-6.5), whereas formation of free cyanide from metal cyanide complexes is comparatively slow. A high rate of cyanide absorption is critical to acute toxicity, and absorption may be retarded by the lower dissociation rates of metal-cyanide complexes. In Arizona, a red-breasted merganser (Mergus senator) was found dead 20 km from the nearest known source of cyanide, and its pectoral muscle tissue tested positive for cyanide. A proposed mechanism to account for this phenomenon involves weak-acid dissociable (WAD) cyanide compounds. Cyanide bound to certain metals, usually copper, is dissociable in weak acids such as stomach acids. It has been suggested that drinking of lethal cyanide solutions by animals may not result in immediate death if the cyanide level is... 

As a class of compounds, the two main toxicity concerns for nitriles are acute lethality and osteolathyrsm. A comprehensive review of the toxicity of nitriles, including detailed discussion of biochemical mechanisms of toxicity and stmcture-activity relationships, is available (12). Nitriles vary broadly in their abiUty to cause acute lethaUty and subde differences in stmcture can greatly affect toxic potency. The biochemical basis of their acute toxicity is related to their metaboHsm in the body. Following exposure and absorption, nitriles are metabolized by cytochrome p450 enzymes in the Hver. The metaboHsm involves initial hydrogen abstraction resulting in the formation of a carbon radical, followed by hydroxylation of the carbon radical. MetaboHsm at the carbon atom adjacent (alpha) to the cyano group would yield a cyanohydrin metaboHte, which decomposes readily in the body to produce cyanide. Hydroxylation at other carbon positions in the nitrile does not result in cyanide release. 

Spectrophotometric deterrnination at 550 nm is relatively insensitive and is useful for the deterrnination of vitamin B 2 in high potency products such as premixes. Thin-layer chromatography and open-column chromatography have been appHed to both the direct assay of cobalamins and to the fractionation and removal of interfering substances from sample extracts prior to microbiological or radioassay. Atomic absorption spectrophotometry of cobalt has been proposed for the deterrnination of vitamin B 2 in dry feeds. Chemical methods based on the estimation of cyanide or the presence of 5,6-dimethylben2irnida2ole in the vitamin B 2 molecule have not been widely used. 

Skin Absorption. Normal skin absorbs HCN slowly. However, 2% HCN in air may cause poisoning in 3 min, 1% is dangerous in 10 min, and 0.05% may produce symptoms after 30 min, even though a gas mask or air mask is worn. Some areas of the body, such as the feet and mucous membranes, are more absorptive than others. Cuts and abrasions absorb cyanide rapidly, and 50 mg of HCN absorbed through the skin can be fatal. 

The gold is then recovered from solution by precipitation with zinc dust, electro deposit, or absorption on carbon. Sodium cyanide is used extensively in organic syntheses, especially in the preparation of nitriles (qv). 

Cyanohydrins are highly toxic by inhalation or ingestion, and moderately toxic through skin absorption (21). AH a-hydroxy nitriles are potential sources of hydrogen cyanide or cyanides and must be handled with considerable caution. Contact with the skin and inhalation should be rigorously avoided. Special protective clothing should be worn and any exposure should be avoided (18,20). The area should be adequately ventilated. Immediate medical attention is essential in case of cyanohydrin poisoning. 

Acrylonitrile (Vinyl cyanide) CH,CHCN Closely resembles HCN in toxic action Poisonous by inhalation, ingestion or skin absorption Emits cyanides when heated or contacted by acids or acid fumes Symptoms flushed face, irritation of eyes and nose, nausea etc. Colourless flammable liquid with mild, faintly pungent odour Elash point 0°C. Dilute water solutions also have low flash points... 

Potassium cyanide KCN On exposure to air, gradually decomposes to release HCN Poisonous by ingestion, inhalation or skin absorption Do not handle with bare hands. Strong solutions may be corrosive to the skin Nonflammable white lumps or crystals Eaint odour of bitter almonds Completely water soluble... 

Sodium cyanide NaCN Poisonous by inhalation, ingestion or skin absorption Do not handle with bare hands Releases HCN slowly with water, more rapidly with acids Nonflammable white granules, fused pieces or eggs Odourless when dry slight almond odour in damp air Completely water soluble... 

Skin" Notation-. The designation "skin" refers to the potential contribution to the overall exposure by the cutaneous route, including mucous membranes and eyes, either by airborne, or more particularly by direct, contact with the substance. Examples of such substances are phenol (cresol and cumene), hydrogen cyanide, and mercury. The "skin" notation is intended to make known the need to prevent cutaneous absorption so that the TLV is not violated. 

Some disadvantages stem from the same phenomena impeded diffusion reduces the maximum practical rate of plating to well below that possible with aquocation baths. The cyanide ion is not entirely stable both oxidation and reduction products accumulate, including carbonate. Carbonate is also formed in the alkaline cyanide baths (all cyanide baths are alkaline except some based on aurocyanides) by absorption of COj from the air, and it is necessary either to replace or purify baths periodically. Much has been made of the toxicity of cyanides, but the other process solutions used in plating are generally extremely toxic and corrosive or caustic, and it is necessary to treat them all with respect. 

A convenient trap (Fig. 3) devised by John R. Johnson for the absorption of hydrogen chloride, or for the elimination of sulfur dioxide, hydrogen cyanide, etc., may be arranged as shown in the figure. The gases are led into a chamber in which a stream of water (from the reflux condenser in this case) flows downward into a large bottle. The bottle is provided with a... 

Procedure. Dissolve 0.0079 g of pure lead nitrate in 1 L of water in a graduated flask. To 10.0 mL of this solution (containing about 50 p.g of lead) contained in a 250 mL separatory funnel, add 75 mL of ammonia-cyanide-sulphite mixture (Note 1), adjust the pH of the solution to 9.5 (pH meter) by the cautious addition of hydrochloric acid (CARE ), then add 7.5 mL of a 0.005 per cent solution of dithizone in chloroform (Note 2), followed by 17.5 mL of chloroform. Shake for 1 minute, and allow the phases to separate. Determine the absorbance at 510 nm against a blank solution in a 1.0 cm absorption cell. A further extraction of the same solution gives zero absorption indicative of the complete extraction of the lead. Almost the same absorbance is obtained in the presence of 100 pg of copper ion and 100 pg of zinc ion. 

In order to concentrate the lead extract, remove the lead from the organic solvent by shaking this with three successive 10 mL portions of the dilute hydrochloric acid solution, collecting the aqueous extracts in a 250 mL beaker. To the combined extracts add 5 mL of 20 per cent ascorbic acid solution and adjust to pH 4 by the addition of concentrated ammonia solution. Place the beaker in a fume cupboard, add 3 mL of the 50 per cent potassium cyanide solution and immediately adjust the pH to 9-10 with concentrated ammonia solution. Transfer the solution to a 250 mL separatory funnel with the aid of a little de-ionised water, add 5 mL of the 2 per cent NaDDC reagent, allow to stand for one minute and then add 10 mL of methyl iso butyl ketone. Shake for one minute and then separate and collect the organic phase, filtering it through a fluted filter paper. This solution now contains the lead and is ready for the absorption measurement. 

The arenediazocyanides have been known since 1879. They played an important role in the Hantzsch-Bamberger debate on the (Z)/( ,)-isomerism of diazo compounds (see Sec. 7.1). When an aqueous solution of a diazonium salt is added to a solution of sodium or potassium cyanide, both in relatively high concentration, at a temperature below 0°C, a yellow to red (Z)-arenediazocyanide starts to crystallize. Hantzsch and Schulze (1895 a) found that these compounds rearrange into the (ii)-isomers, which have a bathochromically shifted visible absorption (see Sec. 7.1). Under strongly alkaline conditions a 1 2 adduct is formed, to which Stephenson and Waters (1939) assigned the structure 6.36. It was never corroborated, however, by modern instrumental analysis. 

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