Cyanogen is a colourless gas, possessing a peculiar characteristic smell, and is very poisonous.
When cyanogen is prepared by heating mercuric cyanide, a residue known as para-cyanogen, (CN)x, is left; this is to be regarded as a polymer of cyanogen.
The chemical analogy of this substance to chlorine was quickly perceived, especially after its investigation by Davy and Gay Lussac. Cyanogen, a compound which in combination behaved very similarly to chlorine and iodine, was isolated in 1815 by Gay Lussac. This discovery of the first of the then-styled " compound radicals " exerted great influence on the prevailing views of chemical composition.
A consequence of this empirical division was that marsh gas, ethylene and cyanogen were regarded as inorganic, and at a later date many other hydrocarbons of undoubtedly organic nature had to be included in the same division.
Instances had already been recorded of cases where a halogen element replaced hydrogen with the production of a closely allied substance: Gay Lussac had prepared cyanogen chloride from hydrocyanic acid; Faraday, hexachlorethane from ethylene dichloride, &c. Here the electronegative halogens exercised a function similar to electro-positive hydrogen.
Cyanogen and hydrocyanic acid, recognizable by their odour, indicate decomposable cyanides.
From this he infers that cyanogen is C: N N :C and not N; C C; N, that hydrocyanic acid is HC N, and acetonitrile CH 3 C; N.
Bladin HC -N (Ber., 1892, 25, p. 183) by the action of acetic)NH anhydride on dicyanophenylhydrazine (formed N: CH from cyanogen and phenylhydrazine), the resulting acetyl derivative losing water and yielding phenylmethylcyanotriazole, which, on hydrolysis, gives the free acid.
CYANAMIDE, NC NH 2j the amide of normal cyanic acid, obtained by the action of ammonia on cyanogen chloride, bromide or iodide, or by the desulphurization of thio-urea with, mercuric oxide; it is generally prepared by the latter process.
Further work on cyanogen and connected substances yielded a great number of interesting derivatives, and he described an improved method for the manufacture of potassium cyanide, an agent which has since proved of enormous value in metallurgy and the arts.
Cloez, Jahresb., 18 53, p. 468); or by the action of tin and hydrochloric acid on cyanogen (T.
Weith, Ber., 1882, 15, p. 1513), and by the spontaneous hydrolysis of an aqueous solution of cyanogen gas.
It may be prepared by heating a mixture of cyanogen and hydrogen to 500°-550° C. (M.
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.
Its aqueous solution is not an electrolyte, and consequently does not give the reactions of the mercury and cyanogen ions.
When heated it yields mercury, cyanogen and paracyanogen.
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.
A large quantity of the salt is now prepared from the "spent oxide" of the gas works, the cyanogen compounds formed in the manufacture of the gas combining with the ferric oxide in the purifiers to form insoluble iron ferrocyanides.
Bueb (Congress of German Gas Industries, March 1900) brings gas (free from tar) into intimate contact with a saturated solution of ferrous sulphate, when a "cyanogen mud" is obtained.
Soc., 1880, 37, p. 740) by the action of cyanogen gas on zinc ethyl.
Cyanogen compounds of chromium, analogous to those of iron, have been prepared; thus potassium chromocyanide, K 4 Cr(CN) 6.2H 2 0, is formed from potassium cyanide and chromous acetate; on exposure to air it is converted into the chromicyanide, K 3 Cr(CN) 6, which can also be prepared by adding chromic acetate solution to boiling potassium cyanide solution.
King, that in the case of the so-called spectrum of cyanogen these tails can be observed.
Another much disputed spectrum is that giving the bands which appear in the electric arc; it is most frequently ascribed to cyanogen, but occasionally also to carbon vapour.
When heated in a current of carbon monoxide or dioxide, it is converted into oxide, some carbon and cyanogen being formed at the same time.
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.
The proof that prussic acid contains hydrogen but no oxygen was a most important support to the hydrogen-acid theory, and completed the downfall of Lavoisier's oxygen theory;, while the isolation of cyanogen was of equal importance for the subsequent era of compound radicles in organic chemistry.
Cyanogen iodide and iodine monoand tri-chloride effect similar decompositions with simultaneous liberation of iodine; sulphuric acid reacts slowly, forming nickel sulphate and liberating hydrogen and carbon monoxide.
It combines with water, forming the hydrates SbC1 5 -1-1 2 0 and SbC1 3.4H 2 O; it also combines with phosphorus oxychloride, hydrocyanic acid, and cyanogen chloride.
Pfliiger has argued that the analogies between living proteid and the compounds of cyanogen are so numerous that they suggest cyanogen as the startingpoint of protoplasm.
Cyanogen and its compounds, so far as we know, arise only in a state of incandescent heat.
Pfliiger suggests that such compounds arose when the surface of the earth was incandescent, and that in the long process of cooling, compounds of cyanogen and hydrocarbons passed into living protoplasm by such processes of transformation and polymerization as are familiar in the chemical groups in question, and by the acquisition of water and oxygen.
It is a brickred powder which explodes when heated to 130° C. Selenium cyanide, Se(CN) 2, is obtained by decomposing silver selenocyanide with cyanogen iodide, or by the action of silver cyanide on a solution of selenium bromide in carbon bisulphide.
Newall has verified the presence of cyanogen in the photosphere, and it had previously served to disprove the solar origin of certain oxygen lines.
Dyson has measured some eight hundred lines in the lower chromosphere and identified them with emission spectra of the following elements: hydrogen, helium, carbon with the cyanogen band, sodium, magnesium, aluminium, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, zinc, strontium, yttrium, zirconium, barium, lanthanum, cerium, neodymium, ytterbium, lead, europium, besides a few doubtful identifications; it is a curious fact that the agreement is with the spark spectra of these elements, where the photosphere shows exclusively or more definitely the arc lines, which are generally attributed to a lower temperature.
The following table will give an approximate idea of the proportions which go to each Nitrogen as ammonia cyanogen in gas and combined in tar in coke .
Cyanogen compounds also are present in the gas, and in large works, where the total quantity is sufficient, their extraction is effected for the production of either prussiate or cyanide of soda.
Cyanogen compounds are extracted either direct from the gas, from the spent oxide or from ammoniacal liquor, and some large gas works now produce sodium cyanide, this being one of the latest developments in the gas chemical industry.
- 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.