A greenish-yellow gas with a suffocating odour. Its preparation and general action have already been described (p. 548).

Action. - When applied for a long time to the skin, as in persons who have to work in an atmosphere containing it, it causes itching, reddening, and inflammation. When applied to the more sensitive mucous membranes of the respiratory passages, it acts as a stimulant or irritant. In a concentrated form it may cause death from spasm of the glottis, or intense bronchitis. In a more dilute form it is used as a stimulant, deodoriser, and disinfectant. The manner of employing it is to put a saucer containing salt, binoxide of manganese, and sulphuric acid on a shelf or high piece of furniture in the sick room, and thus allow the chlorine vapour, which is heavier than air, to diffuse itself through the apartment. When placed on the floor it is of little use.

Liquor Chlori, B.P.; Aqua Chlori, U.S.P. Chlorine Water. - An aqueous solution of chlorine containing at least 0.4 per cent. of the gas U.S.P., or 2.66 grains in 1 fluid ounce = about 0.6 per cent. B.P.

Characters. - A greenish-yellow clear liquid with a strong smell and taste of chlorine. It instantly decolorises dilute solutions of litmus and indigo.

Preparation. - By passing washed chlorine into water (p. 548). The chlorine is directed by the B. and U.S.P. to be prepared from hydrochloric acid and manganese dioxide, instead of from sodium chloride. 4HC1 + MnO2 = Cl2 + MnCl2 + 2H2O.

Impurities. - The chief is too little chlorine. When exposed to light it is apt to be decomposed, the chlorine combining with the hydrogen of the water and forming hydrochloric acid. The chlorine water thus loses strength, and it also becomes weaker by the chlorine escaping when the bottle is imperfectly stoppered or frequently opened. A solution of chlorinated soda or lime may be sometimes substituted for chlorine water.

Tests. - The amount of chlorine is not tested directly but indirectly, by estimating the amount of iodine which a definite quantity of chlorine water liberates from iodide of potassium. In this process, chlorine water (489 grains or 1 fluid ounce B.P., or 35.4 gm. U.S.P.) is mixed with iodide of potassium (20 grains B.P., 0.9 gm. U.S.P.) and water (1 fluid ounce B.P., 20 gm. U.S.P.). The amount of iodine which is set free by the chlorine (2KI + Cl2 = 2KC1 +I2) gives a red colour to the solution, and corresponds in quantity to the chlorine contained in the water. The red solution requires for its de-colorisation 750 grain-measures B.P., or 40 cc. U.S.P. of the volumetric solution of hyposulphite of sodium. The reaction which occurs is :-

Iodine.

Sodium Hyposulphite.

Sodium Iodide.

Sodium Tetrathionate.

Water.

I2

+ 2Na2H2S2O4

= 2NaI

+ Na2S4O6 +

2H2O.

Uses. - Chlorine is used in solution as a lotion to foul-smelling ulcers or cancer; as an application to relieve itching in chronic skin diseases; and as a gargle or wash to the mouth in affections of the mouth, throat, and tonsils, especially where they are accompanied by foetor, as in mercurial ptyalism and ulceration of the tonsils. It is sometimes given internally in cases of blood-poisoning. As an inhalation it has been used in cases of phthisis, it is said with good effect. It is also employed as a stimulant and deodoriser in cases of chronic bronchitis with foetid sputa. (Vide Vapor Chlori, p. 551.)

The aqueous solution is so unstable and liable to lose its strength, that compounds of chlorine from which it can be easily evolved are more convenient for general use. The chief of these are the following compounds with lime and with soda.

Calx Chlorinata, B.P.; Calx Chlorata, U.S.P. Chlorinated Lime. - A product obtained by exposing slaked lime to the action of chlorine gas so long as the latter is absorbed. It possesses bleaching and disinfecting properties. It may be regarded as consisting, chiefly, of a compound of hypochlorite and chloride of calcium (CaCl2O2,CaCl2) or as a direct compound of chlorine and lime, B.P. A compound resulting from the action of chlorine upon hydrate of calcium, and containing at least 25 per cent. of available chlorine, U.S.P.

Characters. - A greyish-white powder having the odour of chlorine and an acrid taste; it absorbs carbonic acid and water when exposed to the air, and at the same time gives off chlorine; it is only partly soluble in water. The solution is alkaline, and possesses bleaching properties (e.g. it bleaches sulphate of indigo).

It is readily decomposed by acids, even by carbonic acid, and thus when exposed to the air chlorine is given off slowly. The addition of a stronger acid causes it to be evolved rapidly. Its probable constitution is

Ca

Cl. OCl.

This is decomposed by water into a mixture of calcium chloride and hypochlorite, and as it is usually moist it may be regarded as usually consisting of a mixture of these substances. On the addition of sulphuric acid, hypochlorous and hydrochloric acids are set free, which reacting on one another yield free chlorine. HCIO + HC1 = C12 + H2O.

Reaction. - The addition of oxalic acid causes the rapid and copious evolution of chlorine and the deposition of oxalate of calcium.

Impurities. - Imperfect saturation with chlorine. It is tested volumetri-cally in a similar way to liquor chlori, the chlorine being set free from it by the addition of hydrochloric acid. The chlorine thus liberated should amount to 30 per cent. B.P., 25 per cent. U.S.P.

Officinal Preparations.

B.P. Liquor Calcis Chlorinatae. Vapor Chlori (p. 551).

U.S.P

Liquor Calcis Chloratae.

Chlorinated lime is used in the preparation of Chloroform.

Liquor Calcis Chlorinatae. Solution of Chlorinated Lime. - It is a solution of 1 lb. to the gallon of water, and when tested volumetrically it should contain 13 grains of available chlorine in 1 fluid cz.

Liquor Sodae Chlorinatae, B.P.; Liquor Sodae Chloratae, U.S.P. Solution of Chlorinated Soda. - (Labarraque's disinfecting fluid.)

Characters. - A colourless alkaline liquid, with astringent taste and feeble odour of chlorine.

Preparation. - By passing chlorine into a solution of sodium carbonate B.P., or by decomposing chlorinated lime by sodium carbonate U.S.P.

Tests. - It behaves like a solution of chlorinated lime, but is not precipitated by oxalic acid nor oxalate of ammonium. (Distinction from and absence of solution of chlorinated lime.)

Dose. - 10 to 20 minims.

Officinal Preparation, B.P.

Cataplasma Sodae Chlorinatae.

Cataplasma Sodae Chlorinatae. - Linseed meal 2; solution of chlorinated soda 1; boiling water 4.

Uses. - Chlorinated lime is chiefly employed as a disinfectant and a deodoriser. In sick rooms some of it is put in saucers, and, according to the rapidity with which the evolution of chlorine is desired, either acid is added to it, or it is simply moistened and exposed to the air, when it is slowly decomposed by the carbonic acid. It is employed also for disinfecting typhoid stools, water-closets, and sewers. For this purpose it is used either in powder or solution. A solution is used to disinfect the sheets and bedding of patients suffering from infectious diseases.

Solutions of chlorinated lime or of chlorinated soda may be employed instead of chlorine water or permanganate of potassium for washing the hands after dissecting or performing post-mortem examinations. They are applied externally to wounds and ulcers of all sorts which have a foetid discharge and a tendency to slough. Not only do they remove the foetor, but they often induce a healthy action in the tissues themselves; and instead of the ulceration or sloughing extending farther and farther, the slough is thrown off and leaves behind it a healthy, healing surface. As the removal of sloughs is aided by heat, we have in the B.P. the poultice of chlorinated soda.

Like chlorine they are destructive to plant life, and they are therefore useful in skin-diseases depending on the presence of parasitic fungi, such as ringworm of the scalp, and in scabies which is due to the presence of a parasitic acarus. As they have a stimulant action on the skin, they are sometimes useful in eczema and prurigo.

They are employed as gargles, or washes to the mouth when foetid ulcers occur in these parts, as in ptyalism or in scarlatina; as an injection into the nose they have been used to lessen the discharge and to remove the foetor in ozaena, a disease in which the discharge from the nostrils is sometimes so disgusting as to be almost unendurable to the patient himself as well as to those around him. They are likewise useful in foetid discharges from the vagina, such as occur when the uterus is the seat of malignant disease.

Internally they have been employed in so-called putrid fevers, when it was imagined there was a special tendency to decomposition in the blood, such as typhus and malignant scarlatina. They have been given more especially in these diseases when there was great prostration of strength, with foetid evacuations and a dry and furred tongue.