Chlorine And' The Hypochlorites

Chlorine gas is set free from chlorinated lime on contact with moisture, or it may be prepared by adding dilute sulphuric acid to a mixture of equal parts of manganese dioxide and sodium chloride. Chlorine water, 0.4 per cent., and the solution of sodium hypochlorite (Labarraque's solution), are employed as gargles, and a solution of potassium hypochlorite (eau de Javelle) is used to bleach linen. These liquids are caustic and are not suitable for application to wounds. Antiformin is an alkaline hypochlorite used to dissolve tissue, blood, pus, and mucus in the examination of sputum for tubercle bacilli.

A favorite procedure for the disinfection of the surgeon's hands is to moisten them and then rub them together with a little chlorinated lime and washing-soda; the soluble sodium hypochlorite and free chlorine are generated, and serve as effective skin germicides. Chlorine is a very irritant gas, and is a powerful permanent bleaching-agent, destroying wall-paper, fabrics, etc.

Theory Of Action

In an investigation of the action of chlorine compounds, Dakin finds no support for the theory that their antiseptic action is due to the liberation of oxygen in the presence of organic matter, but has ascertained that free chlorine converts some of the >NH groups of the proteins into >Nc1 groups, producing new substances which are known as chloramins and are antiseptic.

Chlorinated lime, CaCl2.Ca(OCl)2, is commonly known as "chloride of lime." It has been much employed in privies, sinks, cess-pools, etc., and for the purification of drinking-water. For the latter purpose a level teaspoonful of the powder is dissolved in a pint of water, and of this one teaspoonful is mixed with two gallons of the water to be purified, i. e., 1 part in 2,000,000. In this dilution it gives no taste. Chlorinated lime deteriorates rapidly on exposure to air.

Dakin and Dunham have found para-sulphon-di-chloramino-benzoic acid to be the most suitable agent for the disinfection of drinking-water, a solution of 1: 300,000 being able to sterilize a heavily contaminated water in about thirty minutes, and giving a barely perceptible taste. It keeps well if in tablet form.

The Dakin-Carrel Treatment has become famous as a method for the continuous disinfection of wounds, the antiseptic employed being a solution of sodium hypochlorite (NaOCl) as obtained in Daufresne's modification of Dakin's solution. The formula of this solution as given by Carrel (Jour. Amer. Med. Assoc, December 9, 1916) is as follows:

Preparation Of Dakin's Solution

Daufresne's Technic. - Dakin's solution is a solution of sodium hypochlorite for surgical use, the characteristics of which, established after numerous tests and a long practical experience, are as follows:

(A) Complete Absence Of Caustic Alkali

The absolute necessity for employing in the treatment of wounds a solution free from alkali hydroxide excludes the commercial Javelle water, Labar-raque's solution, and all the solutions prepared by any other procedure than the following:

(B) Concentration

The concentration of sodium hypochlorite must be exactly between 0.45 and 0.50 per cent. Below 0.45 per cent. of hypochlorite the solution is not sufficiently active; above 0.50 per cent. it becomes irritating.

Chemicals Required For The Preparation

Three chemical substances are indispensable to Dakin's solution: chlorinated lime, anhydrous sodium carbonate, and sodium bicarbonate. Among these three products the latter two are of a practically adequate constancy, but this is not the case with the first. Its content in active chlorine (decoloring chlorine) varies within wide limits, and it is absolutely indispensable to titrate it before using it.

Titration Of The Chlorinated Lime

There must be on hand for this special purpose:

A 25 c.c. buret graduated in 0.1 c.c.

A pipet gaged for 10 c.c.

A decinormal solution of sodium thiosulphate (hyposulphite).

The material for the dosage thus provided, a sample of the provision of chlorinated lime on hand, is taken up either with a special sound or in small quantities from the mass which then are carefully mixed.

Weigh out 20 gm. of this average sample, mix it as completely as possible with 1 liter of ordinary water, and leave it in contact for a few hours, agitating it from time to time. Filter.

Measure exactly with the gaged pipet 10 c.c. of the clear fluid; add to it 20 c.c. of a 1: 10 solution of potassium iodid and 2 c.c. of acetic or hydrochloric acid. Drop, a drop at a time, into this mixture a decinormal solution of sodium thiosulphate until decoloration is complete.

The number of cubic centimeters of the hypochlorite solution required for complete decoloration, multiplied by 1.775, gives the weight of the active chlorine contained in 100 gm. of the chlorinated lime.

This figure being known, it is applied to the accompanying table, which will give the quantities of chlorinated lime, of sodium carbonate, and of sodium bicarbonate which are to be employed to prepare 10 liters of Dakin's solution:

Titer of chlorin-ated lime.

Chlorinated lime, gm.

Anhydrous sodium carbonate, gm.

Sodium bicarbonate, gm.

20

230

115

96

21

220

110

92

22

210

105

88

23

200

100

84

24

192

96

80

25

184

92

76

26

177

89

72

27

170

85

70

28

164

82

68

29

159

80

66

30

154

77

64

31

148

74

62

32

144

72

60

33

140

70

59

34

135

68

57

35

132

66

55

36

128

64

53

37

124

62

52

Example: If it required 16.6 c.c. of the decinormal solution of the sodium thiosulphate for complete decoloration, the titer of the chlorinated lime in active chlorine is: 16.6 X 1.775 = 29-7 per cent. The quantities to be employed to prepare 10 liters of the solution will be in this case:

Chlorinated lime ............................................................................

154 gm.

Dry sodium carbonate............................

77 gm.

Sodium bicarbonate...............................

62 gm.

Of crystalline sodium carbonate 220 gm. may be used instead of the 80 gm. of dry carbonate.

Preparation Of Dakin's Solution

To prepare 10 liters of the solution:

1. Weigh exactly the quantities of chlorinated lime, sodium carbonate, and sodium bicarbonate which have been determined in the course of the preceding trial.

2. Place in a 12-liter jar the chlorinated lime and 5 liters of ordinary water, agitate vigorously for a few minutes, and leave in contact for from six to twelve hours, over night, for instance.