The double cyanides of cobalt are analogous to those of iron.
Calcium, or cyanides in a current of nitrogen, e.g.
Ammonia, recognizable by its odour and alkaline reaction, indicates ammoniacal salts or cyanides containing water.
The combination of nitrogen with carbon may result in the formation of nitriles, cyanides, or primary, secondary or tertiary amines.
To form (1) oxides and nitric acids, (2) ammonia, (3) readily decomposable nitrides, (4) cyanides, (5) cyanamides.
The electro-deposition of brass-mainly on iron ware, such as bedstead tubes-is now very widely practised, the bath employed being a mixture of copper, zinc and potassium cyanides, the proportions of which vary according to the character of the brass required, and to the mode of treatment.
The preparation, properties, &c., of cyanides are treated in the article Prussic Acid; reference should also be made to the articles on the particular metals.
The metal is soluble in solutions of chlorine, bromine, thiosulphates and cyanides; and also in solutions which generate chlorine, such as mixtures of hydrochloric acid with nitric acid, chromic acid, antimonious acid, peroxides and nitrates, and of nitric acid with a chloride.
The metal has been obtained by electrolysis of a mixture of caesium and barium cyanides (C. Setterberg, Ann., 1882, 211, p. loo) and by heating the hydroxide with magnesium or aluminium (N.
Sodium is largely employed in the manufacture of cyanides and in reduction processes leading to the isolation of such elements as magnesium, silicon, boron, aluminium (formerly), &c.; it also finds application in organic chemistry.
The salts of this acid, known as cyanides, may be prepared by the action of cyanogen or of gaseous hydrocyanic acid on a metal; by heating the carbonates or hydrooxides of the alkali metals in a current of hydrocyanic acid; by heating alkaline carbonates with carbon in the presence of free nitrogen: BaCO 3 + 4 C + N2 = Ba(NC) 2 + 3C0; by ignition of nitrogenous organic substances in the presence of alkaline carbonates or hydroxides; or by processes of double decomposition.
The alkali and alkaline earth cyanides are soluble in water and in alcohol, and their aqueous solution, owing to hydrolytic dissociation, possesses an alkaline character.
The cyanides of other metals are decomposed by heat, frequently with liberation of cyanogen.
The cyanides are usually reducing agents.
The double cyanides formed by the solution of the cyanide of a heavy metal in a solution of potassium cyanide are decomposed by mineral acids with liberation of hydrocyanic acid and formation of the cyanide of the heavy metal.
Besides these, other double cyanides are known which do not suffer such decomposition, the heavy metal present being combined with the cyanogen radical in the form of a complexion.
The most important members of these classes are the ferroand ferri-cyanides and the nitroprussides.
Organic Cyanides or Nitriles.
- Considerable discussion has taken place as to the structure of the metallic cyanides, since potassium cyanide and silver cyanide react with alkyl iodides to form nitriles and isonitriles respectively, thus apparently pointing to the fact that these two compounds possess the formulae KCN and AgNC. The metallic cyanides are analogous to the alkyl isocyanides, since they form soluble double silver salts, and the fact that ethyl ferrocyanide on distillation yields ethyl isocyanide also points to their isocyanide structure.
The metallic cyanides may be detected by adding ferrous sulphate, ferric chloride, and hydrochloric acid to their solution, when a precipitate of Prussian blue is produced; if the original solution contains free acid it must be neutralized by caustic potash before the reagents are added.
Silver nitrate gives a white precipitate with cyanides, soluble in excess of potassium cyanide.
The simple cyanides share the properties of the acid, except those of platinum and iron.
With these exceptions, the simple cyanides are readily decomposed even by carbonic acid, free prussic acid being liberated.
The double cyanides are innocuous.
The diazo cyanides, C 6 H 5 N 2 CN, and carboxylic acids, C6H5.
On such a hypothesis, the relatively unstable normal diazo hydroxides would be the syn-compounds, since here the nitrogen atoms would be more easily eliminated, whilst the stable iso-diazo derivatives would be the anti-compounds, thus: R N R N HO-N N OH Normal hydroxide Iso hydroxide (Syn-compound) (Anti-compound) In support of this theory, Hantzsch has succeeded in isolating a series of syn - and anti-diazo-cyanides and -sulphonates (Ber.,1895,28, p.666; 1900, 33, P. 2161; 1901, 34, p. 4166).
The isolation of these compounds is a powerful argument in favour of the Hantzsch hypothesis which requires the existence of these three different types, whilst the Bamberger-Blomstrand view only accounts for the forma tion of two isomeric cyanides, namely, one of the normal diazonium type and one of the iso-diazocyanide type.
In organic chemistry he published papers on the decomposition of ammonium oxalate, with formation of oxamic acid, on amyl alcohol, on the cyanides, and on the difference in constitution between nitric and sulphuric ether.
In a note published in 18 r.1 he described the physical properties of this acid, but he said nothing about its chemical composition till 1815, when he described cyanogen as a compound radicle, prussic acid as a compound of that radicle with hydrogen alone, and the prussiates (cyanides) as compounds of the radicle with, metals.
It is reduced to metallic silver by certain metals - zinc, iron, &c. - in the presence of water, by fusion with alkaline carbonates or cyanides, by heating in a current of hydrogen, or by digestion with strong potash solution, or with potassium carbonate and grape sugar.
For the cyanides see Prussic Acid.
- This includes compounds of cyanogen such as hydrocyanic (prussic) acid, cyanides of potassium, sodium, &c., cherry-laurel water, amygdalin, bitter almonds and other chemical and vegetable substances which readily yield hydrocyanic acid.
Other alloys may be produced, such as bronze, or German silver, by selecting solutions (usually cyanides) from which the current is able to deposit the constituent metals simultaneously.
