Hydrogen chloride

“ Hydrogen chloride, as a perfectly dry gas, is a non-conductor of electricity and, at the same time, it is found to be chemically inactive—it does not combine, for instance, with dry ammonia125 or act upon dry calcium carbonate126 or on dry litmus. ”

“ The sodium chloride has obviously been partially decomposed, by the water, into its base and its acid; the decomposition is favored by the high temperature and by the fact that the hydrogen chloride [p180] formed can pass through the steam cushion into the water, while the sodium hydroxide is left behind. ”

“ The hydrochloride N2H4,2HCl crystallises in octahedra, is very soluble in water, but not in alcohol; it fuses at 198°, evolving hydrogen chloride and forming the salt N2H4HCl; when rapidly heated it decomposes with an explosion; with platinic chloride it immediately evolves nitrogen, forming platinous chloride. By the action of alkalis the salts N2H4,2HX give hydrate of amidogen, N2H4,H2O, which is a fuming liquid (specific gravity 1·03) , boiling at 119°, almost without odour, and whose aqueous solution corrodes glass and india-rubber, has an alkaline taste and poisonous properties. ”

“ Perfectly dry hydrochloric acid gas has no action on metals, but in aqueous solution it dissolves many of them with evolution of hydrogen and formation of chlorides.
The salts of hydrochloric acid, known as chlorides, can, in most cases, be prepared by dissolving either the metal, its hydroxide, oxide, or carbonate in the acid; or by heating the metal in a current of chlorine, or by precipitation. The majority of the metallic chlorides are solids (stannic chloride, titanic chloride and antimony pentachloride are liquids) which readily volatilize on heating. ”

“ In moist air it fumes excessively, yielding hydrogen chloride by hydrolysis: TiCl4 + H2O = TiOCl2 + 2HCl, and is decomposed by water with separation of the hydrated oxide. If the compound be added slowly to a large quantity of cold water, and the clear solution warmed, the oxide formed by hydrolysis remains in colloidal solution. ”

“ In the dark, chlorine and hydrogen are simply chlorine and hydrogen; in the sunlight they combine as if by magic into a totally different substance. By the same unexplained power, the sun frequently does just the opposite work; instead of combining two substances to make one new product, the sun may separate or break down some particular substance into its various elements. For example, if the sun's rays fall upon silver chloride, a chemical action immediately begins, and as a result we have two separate substances, chlorine and silver. ”

“ With chlorine, hydrogen forms a compound called muriatic, or hydrochloric acid gas. It cannot easily be formed by the direct union of its elements, but is procured from some compound in which it exists ready formed. Common salt (chloride of sodium) is generally employed; and when acted on by strong [41] sulphuric acid (or oil of vitriol) , the gas is disengaged in abundance. It must be collected over mercury, for water absorbs it, forming the liquid muriatic, or hydrochloric acid.
A lighted taper plunged into this gas is instantly extinguished. It is very dangerous to animal life if respired. ”

“ These two tests—viz., the production of chlorine by the one, and the production of hydrogen by the other—separate and reveal the constituent parts of the acid. Hydrochloric acid, in common with chlorides, gives a dense precipitate with silver nitrate. The precipitate is insoluble in nitric acid, but soluble in ammonia; it melts without decomposition. Exposed to the light, it becomes of a purple or blackish colour. Every 100 parts of silver chloride are equal to 25·43 of hydrochloric acid, HCl, and to 63·5 parts of the liquid acid of specific gravity 1·20. ”

“ With metals chlorine gives salts (such as sodium chloride, &c.) ; with hydrogen a very energetic and monobasic acid HCl, and the same quantity of chlorine is able by metalepsis to replace the hydrogen; with oxygen it forms unstable oxides of an acid character. These properties of chlorine are possessed by three other elements, bromine, iodine, and fluorine. They are members of one natural family. Each representative has its peculiarities, its individual properties and points of distinction, in combination and in the free state—otherwise they would not be independent elements ”

“ The rate of evolution of the gas is regulated by the amount of heat applied, and the gas is collected by displacement of air. As the equations show, only half of the chlorine present in the hydrochloric acid is liberated.
Fig. 53
2. Electrolytic method. Under the discussion of electrolysis (p. 102) it was shown that when a solution of sodium chloride is electrolyzed chlorine is evolved at the anode, while the sodium set free at the cathode reacts with the water to form hydrogen, which is evolved, and sodium hydroxide, which remains in solution. ”

“ It is tasteless, colourless and odourless gas, which is exceedingly stable and inert. It may be condensed and yields a solid which melts at -55° C. Sulphuretted hydrogen decomposes it with formation of hydrofluoric acid and liberation of sulphur. Sulphur chloride, S2Cl2, is obtained as a by-product in the manufacture of carbon tetrachloride from carbon bi sulphide and chlorine, and may also be prepared on the small scale by distilling sul hur in a chlorine gas, or by the action of sulp-hur on sulphuryl ciiloride in the presence of aluminium chloride (O. Ruff) . ”

“ Hydrogen and oxygen may also be produced electrolytically as gases, and their respective reducing and oxidizing powers at the moment of deposition on the electrode are frequently used in the laboratory, and to some extent industrially, chiefly in the field of organic chemistry. Similarly, the formation of organic halogen products may be effected by electrolytic chlorine, as, for example, in the production of chloral by the gradual introduction of alcohol into an anode cell in which the electrolyte is a strong solution of potassium chloride. ”

“ It was first obtained, in an impure condition, in 1828 by A. A. B. Bussy (1794–1882) and F. Wöhler by the reduction of the chloride with potassium, and in 1855 H. J. Debray prepared it, in a compact state, by reducing the volatilized chloride with melted sodium, in an atmosphere of hydrogen. ”

“ If, however, no porous division be used to prevent the intermingling by diffusion of the anode and cathode solutions, a complicated set of subsidiary reactions takes place. The chlorine reacts with the caustic soda, forming sodium hypochlorite, and this in turn, with an excess of chlorine and at higher temperatures, becomes for the most part converted into chlorate, whilst any simultaneous electrolysis of a hydroxide or water and a chloride (so that hydroxyl and chlorine are simultaneously liberated at the anode) also produces oxygen-chlorine compounds direct. ”

“ LeRoy [7] has proposed the use of hexamethyltripara-aminotriphenylmethane for detecting and estimating free chlorine. On the addition of a hydrochloric acid solution of this compound to a sample containing free chlorine a [84] violet colouration is produced that can be matched in the usual way with standards. It is stated that 0.03 p.p.m. of free chlorine gives a distinct colouration and that the reagent reacts very slowly with nitrites and is quite unaffected by hydrogen peroxide.
The starch-iodide and o-tolidine reactions are affected by oxidising agents or reducible substances ”

“ On allowing chlorine to act upon any animal or vegetable matter, it decomposes a certain quantity of water and seizes its hydrogen, forming hydrochloric acid. The oxygen set free by this reaction is transformed into ozone, which in its turn lays hold of hydrogen present in organic matter.
Actual experiment in England has demonstrated the great advantages of the hammock system of conveying invalids by railway. The invalid suffers neither jar nor jolt. ”

“ At ordinary temperatures it unites directly with many other elements; thus with hydrogen, combination takes place in direct sunlight with explosive violence; arsenic, antimony, thin copper foil and phosphorus take fire in an atmosphere of chlorine, forming the corresponding chlorides. Many compounds containing hydrogen are readily decomposed by the gas; for example, a piece of paper dipped in turpentine inflames in an atmosphere of chlorine, producing hydrochloric acid and a copious deposit of soot; a lighted taper burns in chlorine with a dull smoky flame. ”

“ There is one more fact of a chemical nature in reference to chlorine which it would be unwise to throw aside, as it possesses some degree of interest. When the chemist wishes to decompose water, or in other words to liberate hydrogen from oxygen, he has no better agent to effect the purpose than this greenish-coloured gas, because it has such a strong affinity for hydrogen, which is one of the most characteristic properties of chlorine. Mix them together, and they combine with explosive violence if they are exposed to27 the beams of the sun. ”

“ When free chlorine is present it combines with the hydrogen as produced and so enables more copper to dissolve and produces a permanent flow of current. The current produced is a function of the depolarizing action, i.e. of the free chlorine, and is indicated by the current meter which is graduated in parts per million of available chlorine. The usual range of instrument is 5 p.p.m. and each division of the scale is equal to one-tenth of one part per million. ”

“ About 6 parts of the salt are dissolved by 100 of water at 15°, the solubility increasing with the temperature, so that at 100° nearly 60 parts dissolve; if strong sulphuric acid be dropped on the crystals, peroxide of chlorine is evolved; when rubbed with sulphur in a mortar, potassic chlorate detonates. When the salt is heated strongly, it first melts, and then decomposes, yielding oxygen gas, and is transformed into the perchlorate. If the heat is continued, this also is decomposed, and the final result is potassic chloride. ”

“ Dichloramine is unknown but nitrogen chloride has been prepared and is a highly explosive yellow oil that decomposes slowly when kept under water in the ice box. NCl3 can be easily prepared by passing chlorine gas into a solution of ammonium chloride and this process would suggest that a method might be found of utilising chlorine and ammonia as gases for the production of nitrogen trichloride as a germicide for water chlorination. ”

“ One volume of chlorine unites with one volume of hydrogen, forming two volumes of hydrochloric acid; no condensation occurs in the act of union.
Hydrochloric acid may also be formed by transmitting moist chlorine through a red-hot porcelain tube; oxygen being at the same time liberated.
Prep. Hydrochloric acid, save for the purposes of illustrative experiment, is never obtained by any of the above processes. An easy mode of procuring it, when required for laboratory use, is to heat the ordinary aqueous solution of the acid in a flask, and to collect the gas, which is given off by displacement. ”

“ Chlorine, although one of the most widely distributed elements known to chemists, is never found in the free condition in nature; it exists in enormous quantities in combination with sodium, potassium, calcium, magnesium, etc. As sodium chloride, common salt, it occurs in practically inexhaustible quantities in sea water together with smaller quantities of other chlorides. ”

“ But most of the chlorine is utilized for the production of bleaching-powder, of bleach-liquor, and of chlorate of potash.
Bleaching-powder is a compound obtained by the action of free chlorine on hydrated lime, containing a slight excess of water at ordinary temperatures or slightly above these. Its composition approaches the formula CaOCl2, and it is regarded as a double salt of calcium chloride and hypochlorite, which by the action of water splits up into a mixture of these salts. It always contains a certain quantity of chemically combined water and also an excess of lime. ”

“ A large excess must be used in disinfecting, otherwise the chlorine may simply oxidise fœcal or other organic matter, and not effectually destroy contagia.
Methods of Use— (a) As a gas, by the action of hydrochloric acid on strong chloride of lime. The molecular density of chlorine is 35·5, of formic aldehyde 15, of sulphurous acid 32; and the rate of diffusion of gases being inversely to the square-root of their densities, clearly chlorine does not compare favourably as a gas with formic aldehyde. The bleaching effect of chlorine on coloured articles of apparel is a disadvantage. ”

“ The specific chemical actions peculiar to acids are therefore to be attributed to the hydrogen-ion just as the actions common to all chlorides are to be regarded as those of the free chlorine-ions. In like manner, the reactions characteristic of bases in solution are to be attributed to the negatively charged hydroxyl-ions (OH–) , which result from the dissociation of this class of bodies.
A solution has an acid reaction when it contains an excess of hydrogen-ions, and a basic reaction when it contains an excess of hydroxyl-ions. ”

“ These compounds also afford examples of the fact that, generally speaking, those compounds are most readily formed, and are most stable, in the formation of which the most heat is developed. Thus, chlorine enters into reaction with hydrogen, and removes hydrogen from hydrogenized bodies, far more readily than bromine; and hydrochloric acid is a far more stable substance than hydrobromic acid, hydriodic acid being greatly inferior even to hydrobromic acid in stability. ”