It is decomposed by the halogens, with liberation of sulphur.
Group VII.: H (?), monovalent; the halogens F, Cl, Br, I, usually monovalent, but possibly also triand pentavalent; Mn, divalent and trivalent, and possibly heptavalent in permanganates.
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.
Long-continued treatment with halogens may, in some cases, result in the formation of aromatic compounds; thus perchlorbenzene, C 6 C1 6, frequently appears as a product of exhaustive chlorination, while hexyl iodide, C 6 H 13 I, yields perchlorand perbrom-benzene quite readily.
Methods for the estimation of the halogens and sulphur were worked out by L.
The halogens may be sometimes detected by fusing with lime, and testing the solution for a bromide, chloride and iodide in the usual way.
Beilstein determines their presence by heating the substance with pure copper oxide on a platinum wire in the Bunsen flame; a green coloration is observed if halogens be present.
The space a must allow for the inclusion of a copper spiral if the substance contains nitrogen, and a silver spiral if halogens be present, for otherwise nitrogen oxides and the halogens may be condensed in the absorption apparatus; b contains copper oxide; c is a space for the insertion of a porcelain or platinum boat containing a weighed quantity of the substance; d is a copper spiral.
The oxidation, which is effected by chromic acid and sulphuric acid, is conducted in a flask provided with a funnel and escape tube, and the carbon dioxide formed is swept by a current of dry air, previously freed from carbon dioxide, through a drying tube to a set of potash bulbs and a tube containing soda-lime; if halogens are present, a small wash bottle containing potassium iodide, and a U tube containing glass wool moistened with silver nitrate on one side and strong sulphuric acid on the other, must be inserted between the flask and the drying tube.
The process is therefore adapted to the simultaneous estimation of carbon,hydrogen, the halogens and sulphur.
The halogens may be estimated by ignition with quicklime, or by heating with nitric acid and silver nitrate in a sealed tube.
19, p. 1910) determines sulphur and the halogens by oxidizing the substance in a current of oxygen and nitrous fumes, conducting the vapours over platinum foil, and absorbing the vapours in suitable receivers.
38, p. 1 434) has devised a method in which the oxidation is effected by sodium peroxide; the halogens,phosphorus and sulphur can be determined by one operation.
The thermal effects of the halogens are: chlorine =15.13 calories, bromine = 7.68; iodine = - 4.25 calories.
When heated with the halogens, acetophenone is substituted in the aliphatic portion of the nucleus; thus bromine gives phenacyl bromide, C6H6CO.CH2Br.
Siemens and Halske have proposed the addition of oxidizing agents such as free halogens, to prevent the formation of zinc hydride, to which they attribute the formation of zincsponge.
It combines directly with the halogens, and dissolves in cold dilute sulphuric acid, in hot strong hydrochloric acid and in aqua regia, but less readily in nitric acid.
Bismuth combines directly with the halogens, and the elements of the sulphur group. It readily dissolves in nitric acid, aqua regia, and hot sulphuric acid, but tardily in hot hydrochloric acid.
Sodium combines directly with the halogens to form salts which are soluble in water and crystallize in the cubic system.
As unsaturated compounds they can combine with two monovalent atoms. Hydrogen is absorbed readily at ordinary temperature in the presence of platinum black, and paraffins are formed; the halogens (chlorine and bromine) combine directly with them, giving dihalogen substituted compounds; the halogen halides to form monohalogen derivatives (hydriodic acid reacts most readily, hydrochloric acid, least); and it is to be noted that the haloid acids attach themselves in such a manner that the halogen atom unites itself to the carbon atom which is in combination with the fewest hydrogen atoms (W.
Replacement of -NH 2 by halogens and by the - CN and - CNO groups :- The diazonium salt is warmed with an acid solution of the corresponding cuprous salt (T.
Halogen acids convert it into monohalogen fatty acids, and the halogens themselves convert it into dihalogen fatty acids.
They behave as unsaturated compounds, combining with oxygen to form peroxides and with the halogens to form triarylmethane halides.
Soc., 1904, p. 203) have made an exhaustive study of its reactions, and find that it is decomposed by the halogens (dissolved in carbon tetrachloride) with liberation of carbon monoxide and formation of a nickel halide.
All four of the halogens unite with hydrogen, but the affinity for hydrogen decreases as the atomic weight increases, hydrogen and fluorine uniting explosively at very low temperatures and in the dark, whilst hydrogen and iodine unite only at high temperatures, and even then the resulting compound is very readily decomposed by heat.
The hydrides of the halogens are all colourless, strongly fuming gases, readily soluble in water and possessing a strong acid reaction; they react readily with basic oxides, forming in most cases well defined crystalline salts which resemble one another very strongly.
Silver combines with the free halogens on heating and also with sulphur.
It is a very stable compound, chromic and nitric acids being without action upon it, whilst the halogens only yield substitution derivatives with difficulty.
The element combines directly with the halogens, sulphur and selenium, and most of the metals burn in its vapour forming phosphides.
It is stable towards halogens at ordinary temperature.