Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/566

Rh 554 CHEMISTRY [ORGANIC. C 2 H 5 H H Ethylphosphine. Bi Triethylbismnthlne. C 2 H 5 Triethylphosphine. f- 5 C 1 TT cX Cl As 1 CH 3 (H Dimetliylarsine. C 2 H 5 C 2 H 5 C 2 H 5 U Tetrethylstibonium Tetrethylphosphonlum chloride. iodide. (H Diacetamide. C 2 H 3 O C 2 H 3 O Triucetamide. N 2 ^H XIV. Amides. These compounds are analogous to the amines, being derived from ammonia by the substitution of acid radicles for hydrogen : fH (C 2 H 3 O (C 2 H 3 O (H JH Ammonia. Acetamide. f(c 4 H 4 o 2 )&quot; N 2 ^(C 4 H 4 2 r H .H Succinamlde. Trisuccinamide. The amides may also be written as compounds of acid radicles with amidogen (NH 2 ), imidogen (NH)&quot;, and nitro gen N&quot; : C 2 H 3 O.NH 2 ,(C 2 H 3 0) 2 .(NH)&quot;,(C 2 H 3 0) 3 N &quot;;(C 4 H 4 2 )&quot;.NH Acetamide. Diacetamide. Triacetamide. Succinimide. The fourteen families now enumerated, although com prising most of the known organic substances, still leave outstanding a large number of compounds, of which the constitution has not yet been determined, and which consequently cannot be referred to any of the above groups. We propose to consider briefly the individual families in succession, describing the mode of preparation and properties of the most important members of each family, and then proceeding to the consideration of the unclassed organic compounds. CYANOGEN AND ITS COMPOUNDS. The compound which in its chemical behaviour most closely resembles inorganic substances, and which forms as it were a connecting link between these and organic bodies, is the radicle cyanogen. Before proceeding, there fore, to the systematic consideration of the great organic families, cyanogen and its compounds may be conveniently treated of. Cyanogen, 1 CN or Cy, in the free state Cy 2, is generally prepared by heating the cyanide of some heavy metal (usually mercury) ; HgCy 2 = Hg + Cy 2. A brown sub stance, most probably a polymeride of cyanogen, known as paracyanogen, is always formed in this reaction. Cyanogen is a colourless gas, having a pungent odour resembling that of bitter almond oil. It burns in air with a purple flame, and is extremely poisonous. The gas is condensable into a liquid under a pressure of about 4 atmospheres. The liquid boils at - 2 1 C., and solidifies at - 34 C. Water absorbs about 4 volumes of the gas in the cold. The aqueous solution decomposes on standing, ammonium oxalate being the chief product of the reaction : C 2 N 2 + 4OH 2 = (NH 4 ) 2 C 2 O 4. At the same time small quantities of urea, ammonium carbonate, and cyanide are formed. The addition of a mineral acid to the solution greatly retards the decomposition, oxamide being then pro duced : C 2 N 2 + 20H 2 = C 2 2 (NH 2 ) 2. Conversely, when ox- amide or ammonium oxalate is heated cyanogen is produced (NH 4 ) 2 C 2 4 -40H 2 = C 2 N 2 ; C 2 O 2 (NH 2 ) 2 - 20H 2 = C 2 N 2. 1 From Kvavts, blue, because of the colour of many of its com pounds. In its chemical relationships cyanogen is the exact analogue of the halogen elements. Its compounds with metals or positive radicles are called cyanides. Compounds of cyanogen with Cl, Br, I, S, OH, and NH 2 are known, and are remarkable for their polymeric modi fications. The following is a list of the more important compounds : Cyanogen chloride, CNC1 Cyanuric chloride, C 3 N 3 C1 3 Cyanogen bromide, CNBr Cyanuric bromide, C 3 N 3 Br 3 Cyanogen iodide, CN1 Cyanogen sulphide, C 2 N 2 S Cyanogen selenide, C 2 N 2 Se Cyanic acid, CNOH Cyanuric acid, C 3 N 3 3 H 3 Sulphocyanic acid, CNSH Cyauamide, CN(NH 2 ) Dicyanainide, C 2 N 2 (NH 2 ) 2 Cyanuric amide, C 3 N 3 (NH 2 ) 3 Ammelide, C 3 N 3 (NH 2 )(OH) 2 Ammeline, C 3 N 3 (NH 2 ) 2 OH Hydrogen Cyanide, or Hydrocyanic or Prussic Acid, HCN or HCy. This compound is formed synthetically by passing electric sparks through a mixture of nitrogen and ethnic gases: C 2 H 2 + N 2 = 2HCN. In practice benzene vapour may be used instead of pure ethine, as it is partially resolved into the latter substance by the action of the spark. The anhydrous acid is also obtained by passing dry hydrogen sulphide over mercuric cyanide. The aque ous solution of the acid is prepared by the action of acids upon metallic cyanides : HC1 + KCN = KC1 + HCN ; by the action of ammonia on chloroform: NH 3 + CHC1 3 = HCN + 3HC1 ; and also (most conveniently) by heating a mixture of 5 parts of potassium ferrocyanide with 3 parts of sulphuric acid and 4 parts of water. The pure acid is a colourless liquid, having an odour of bitter almonds ; it is a most violent poison. Its boiling- point is 26 5 C. and its point of solidification - 15 C. The pure acid and its strong aqueous solution are both inflanv mable, burning in air with a violet flame. Both the anhy drous and aqueous acids are very unstable, the fonneJ decomposing into ammonia and a brown substance, and the latter undergoing the same decomposition with the additional formation of ammonium formate. Small quan tities of formic or of a mineral acid prevent this decom position, but on mixture with strong acids, a complete decomposition into formic acid ensues : HCN + 20H 2 + HC1 - H.COOH + NH 4 C1 Hydrocyanic water Hydrochloric Formic Ammonium acid. acid. acid. chloride. Alkalies induce a similar change, alkaline formate and free ammonia being produced. When ammonium formate is heated, the inverse reaction takes place : HCO(ONH 4 ) - 20H 2 = HCN Ammonium wfi. Hydrocyanic formate. acid. A polymeride, H 3 C 3 N 3, is known. Metallic Cyanides. Cyanogen being a monad radicl forms, like Cl, Br, and I, a series of salts typified by the formula? M Cy, M&quot;Cy 2, M&quot; 2 Cy 6 , M n Cy B. Of these the most important is potassium cyanide, which can be formed by passing nitrogen over a mixture of red hot carbon and potassium carbonate : K 2 C0 3 + 4C + N 2 = 2KCN + SCO. This salt is also produced by heating potassium ferrocyanide either alone or mixed with potassium carbonate. Most of the metallic cyanides can be prepared by the action of hydrocyanic acid upon the oxides and hydroxides of the metals, or by double decomposition. The cyanides have a remarkable tendency to form double salts, such, for example, as the double cyanide of potassium and silver, KCy,AgCy. Of these double cyanides a certain number are decom posed by the action of a mineral acid yielding free HCy and salts of the acid : KCN, AgCN + 2HN0 3 = KN0 3 + AgN0 3 + 2HCN,