Chlorine

“ 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. ”

“ 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. ”

“ 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. ”

“ For military camps where a standpipe usually provides a reasonable contact period, it has been found good practice to add sufficient chlorine to give a rich blue colour with the starch-iodide reagent and subsequently reduce the dosage gradually until the water, after standing one hour, gives but a faint reaction to the test reagent. ”

“ Very dilute solution of chlorine, or of chloride of lime or soda, followed by a powerful emetic, or the stomach-pump. When the vapour has been respired, free exposure to fresh air, with the head a little elevated, and copious affusions of cold water, with moderate draughts of brandy-and-water, and the use of the smelling-bottle (ammoniacal) should be adopted. If need be, artificial respiration should be attempted, and the air around the patient should be slightly impregnated with the fumes of chlorine or chloride of lime. ”

“ Dilute solutions of chlorine have been used as intestinal antiseptics in the treatment of typhoid fever without producing irritation of the mucous lining and the usual dose for this treatment is one grain of chlorine. Before taking a medicinal dose of chlorine 140 gallons of water containing 0.1 p.p.m. would have to be consumed, a quantity greater than is ordinarily drunk in a year. ”

“ 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. ”

“ 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 chlorine leaves the furnace mixed with much hydrochloric acid, nitrogen, and air. The gaseous mixture is drawn by a chimney draught through the coke towers, as in the making of salt-cake. By this contrivance the hydrochloric acid is recovered, yielding a solution strong enough to react upon fresh manganese in the still. The diluted chlorine may be made to ascend leaden towers, where it comes in contact with a shower of milk of lime, which absorbs the gas and forms ordinary bleaching liquid, whilst sometimes it is employed in the production of potassium chlorate. ”

“ The evolution of chlorine is promoted by occasionally renewing the exposed surface, by stirring it with a piece of stick, and after it becomes scentless, by the addition of a little acid, as strong vinegar, or hydrochloric acid, or oil of vitriol, largely diluted with water. ”

“ A great deal of the chlorine required in the chemical industries is now made in this way in connection with the manufacture of sodium hydroxide.
Physical properties. Chlorine is a greenish-yellow gas, which has a peculiar suffocating odor and produces a very violent effect upon the throat and lungs. Even when inhaled in small quantities it often produces all the symptoms of a [Pg 180] hard cold, and in larger quantities may have serious and even fatal action. It is quite heavy (density = 2.45) and can therefore be collected by displacement of air. ”

“ But on comparing it with chlorine prepared in other ways he perceived a difference; its solution in water was of lemon yellow or orange colour; when treated with mercury it becomes of a brilliant yellow green. It is, moreover, highly explosive, especially when heated, even at the warmth of the hand, when it loses its vivid colour, and is resolved into a mixture of oxygen and chlorine. Metals, arsenic, phosphorus, charcoal, nitric oxide, act upon it in a manner different from that of chlorine. ”

“ Chlorine does not occur free in nature, but its compounds are widely distributed. For the most part it occurs in combination with the metals in the form of chlorides, those of sodium, potassium, and magnesium being most abundant. Nearly all salt water contains these substances, particularly sodium chloride, and very large salt beds consisting of chlorides are found in many parts of the world. ”

“ Thus chlorine, in acting on marsh gas, CH4, forms four compounds, CH3Cl, CH2Cl2, CHCl3, and CCl4, and it may be established by direct experiment that the substance CH3Cl (methylic chloride) precedes the remainder, and that the latter proceed from it by the further action of chlorine. And this substance, CH3Cl, is formed by the reaction of equal volumes of [312] marsh gas, CH4, and chlorine, Cl2, according to the equation CH4 + Cl2 = CH3Cl + HCl. A great number of similar cases are met with amongst organic—that is, carbon—compounds. ”

“ 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. ”

“ The rate of flow is adjusted to the temperature of the hypochlorite solution leaving the cell but under normal conditions it is stated that the cell described will pass 40 gallons per hour with a consumption of 70 amperes and produce 21⁄2 pounds of chlorine per hour. This is equal to 8 pounds of salt and 3.08 kilowatt hours per pound of chlorine. After the cells have been operated for several months the efficiency usually falls and 10-11 pounds of salt and 3.5-3.7 kilowatt hours are required for the production of one pound of chlorine. ”

“ The details of the technique employed cannot be given but it may be stated that the concentration of chlorine employed is always more than sufficient and that residual tastes and odours are regarded as secondary considerations. Treated water is always tested by the starch-iodide method and a bacteriological examination is frequently made by mobile laboratories. ”

“ The chlorine is generally combined with lime to make chloride of lime or bleaching powder. In the chemical works of Germany the amalgamation of chlorine and lime was omitted, the chlorine being liquified under pressure in tanks. This liquid chlorine was a cheap preparation used largely for bleaching linens and cloth of various kinds manufactured in the districts in which we were fighting. The bleacheries were silent and there was no longer any use in the cloth industry for the German chlorine gas, so the Germans having plenty of it on hand no doubt decided to use it against the Allies. ”

“ A number of different methods of sterilisation have been tried, but so far as the existing knowledge of the subject extends, the application of chlorine in one form or another is generally admitted to be the most efficient and economical process. The chlorine may be applied in the form of a solution of chloride of lime, or as a hypochlorite of sodium, or of magnesium. ”

“ Chlorine gas, prepared in the ordinary manner, is slowly passed into a cold solution of ferrocyanide of potassium, 1 part, in water, 10 parts, with constant agitation, until the liquid appears of a deep reddish-green colour, or of a fine red colour by transmitted light, and ceases to give a blue precipitate, or even a blue tinge, to a solution of ferric chloride, an excess of chlorine being carefully avoided; the liquor is next evaporated by the heat of steam or boiling water, until a pellicle forms upon the surface, when it is filtered, and set aside to cool ”

“ This is seen in the solubility of the salts. Those metals whose chlorides are insoluble form soluble fluorides, while many of the metals which form soluble chlorides form insoluble fluorides.
Compounds of chlorine with oxygen and hydrogen. Chlorine combines with oxygen and hydrogen to form four different acids. They are all quite unstable, and most of them cannot be prepared in pure form; their salts can easily be made, however, and some of them will be met with in the [Pg 187] study of the metals. The formulas and names of these acids are as follows:
Oxides of chlorine. ”

“ 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 ”

“ Liquid chlorine practically eliminates all labour costs because of the simplicity of the apparatus and the concentrated form of the sterilising agent. The apparatus is so compact that all the cylinders and regulating apparatus required for delivering 200 pounds of gas per day can be placed in an area of about 50 square feet and it can consequently be almost invariably accommodated in locations where the trifling amount of attention required can be obtained without extra cost. ”

“ 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. ”

“ Chlō′ric, of or from chlorine.—n. Chlō′ride, a compound of chlorine with some other substance, as potash, soda, &c.—v.t. Chlō′ridise, to convert into a chloride: (phot.) to cover with chloride of silver—also Chlō′ridate.—n. Chlorinā′tion, the process of getting gold, &c., out of ore by the use of chlorine.—v.t. Chlō′rinise, to combine or otherwise treat with chlorine—also Chlō′rinate.—ns. Chlō′rite, a mineral consisting of silica, alumina, &c., in variable proportions—it is of a green colour, rather soft, and is easily scratched with a knife ”

“ In these early experiments, the bleacher had to make his own chlorine and the goods were bleached either by exposing them in chambers to the action of the gas or by steeping them in its aqueous solution. If we consider the inconveniences which must have arisen in working with such a pungent substance as free chlorine, with its detrimental effect on the health of the work-people, it will be readily understood that the process did not at first meet with any great amount of success. ”

“ Again, the greenish-yellow and intensely poisonous gas, chlorine, unites in definite proportions by weight with the soft, wax-like, and highly poisonous metal sodium to produce the white crystalline solid chloride of sodium (common salt) , a compound which, except in very large quantities, is not only not poisonous, but actually beneficial to health.
Such combinations are called chemical compounds, and the force which binds their constituents together is distinguished from all other attractive forces by the term affinity or chemical affinity. ”

“ Some Dutch metal, or powdered antimony, or a bit of phosphorus, immediately takes fire when introduced into a bottle containing chlorine gas, forming a series of compounds termed chlorides, and demonstrating by the evolution of heat and light, the energetic character of chlorine, and that oxygen is not the only supporter of combustion; chlorine gas has even, in some cases, greater chemical power, because some time elapses before phosphorus will ignite in oxygen gas, whilst it takes fire directly when placed in a bottle of chlorine. ”