Sodium hypochlorite

“ Hyclorite.—This is a solution of chlorinated soda, 100 gm. of which is said to contain sodium hypochlorite 4.05 gm., sodium chlorid 3.20 gm., calcium hydroxid 0.25 gm., inert ingredients 0.92 gm. It is declared to contain, when placed on the market, not less than 3.85 per cent. of available chlorin, and to deteriorate at the rate of about 12 per cent. per year. ”

“ Sodium hypochlorite can be prepared by the electrolysis of brine solution in the presence of carbon electrodes, having no diaphragm in the electrolytic cell, and mixing the anode and cathode products by agitating the liquid. ”

“ The raison d’être of the increased activity is obscure but it is possible that the salt renders the organisms more susceptible to the action of the germicide.
Ammonia, though decreasing the hydrogen ion concentration of bleach and other hypochlorite solutions, markedly increases the velocity of the reaction; chlorinated derivatives of ammonia (chloramines) , which have a specific germicidal action, are formed. These will be discussed at length in Chapter IX, p. 115.
Rideal [6] has shown that the addition of ammonia to sodium hypochlorite destroys the bleaching activity in acid solution. ”

“ At the end of the contact period about 90 per cent of the added chlorine was unabsorbed and was destroyed by the addition of sodium bisulphite. Bassenge [16] followed up the work of Traube and that of Sickenberger and Kauffman, who had shown that it was possible to destroy cholera vibrio in Nile water by means of sodium hypochlorite. Bassenge used higher concentrations than Traube and found it possible to destroy B. typhosus and B. coli in ten minutes with 60-90 p.p.m. of available chlorine. The excess was destroyed by adding calcium bisulphite. ”

“ 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. ”

“ Thus it will be seen that this specification clearly described a process by which the chlorides of sodium and potassium, and of the metals of the alkaline earths (chloride of magnesium, for example) , may be converted into hypochlorites by electrolysis, and the hypochlorite solution obtained used for the purposes of bleaching. ”

“ When the partial or total conversion of the liquid has been effected (this being ascertained by chlorometric tests) , the pump, P, is set rapidly in operation, and, as a consequence, draws up the chloride of sodium from the bottom of the vessel, C, to the lower part of the electrolyzer, A. The hypochlorite that has formed passes through the tube, D (as a natural consequence of the elevation of the level of the liquid in A brought about by the entrance of a new supply of chloride) , and distributes itself throughout the vessel, C, where it acts upon the textile material. ”

“ It is soluble in acids, and in the moist condition is also soluble in concentrated alkalis. A hydrated rhodium dioxide, RhO2·2H2O, is formed when chlorine is passed into a solution of the sesquioxide in concentrated caustic potash, or by adding an alkaline hypochlorite to a concentrated alkaline solution of rhodium and sodium chlorides. ”

“ Add 10 c.cms. of a 5 per cent solution of potassium iodide and 0.5 c.cm. glacial acetic acid and titrate with sodium thiosulphate (24.8 grms. of the C.P. crystalline salt and 1 c.cm. of chloroform per litre) using a starch solution as indicator. Each cubic centimetre of thiosulphate used = 1.755 per cent of available chlorine (1 c.cm. N/10 sodium thiosulphate = 0.00355 grm. available chlorine) .
Penot’s Method. Dilute the hypochlorite solution with 15 c.cms. of water and titrate with a solution of N/10 sodium arsenite using starch-iodide paper as an external indicator. Each c.cm. ”

“ They who gape, horror-struck, at the endless revelations of chemistry, without giving reason time to act, err in the second manner. Led away by the brilliant hues and wonderful transformations of the laboratory, they forget the size of the world outside, in which these changes are enacted, and the quiet way in which Nature works. The breath of chlorine is deadly, but we daily eat it in safety, wrapped in its poison-proof envelope of sodium, as common salt. Carbonic acid is among the gases most hostile to man, but he drinks it in soda-water or Champagne with impunity. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ This has been found by the author to be also true for calcium hypochlorite (bleach) . If the bleaching effect is due to oxidation, the oxidising power of hypochlorites must be considered to be destroyed by the addition of ammonia. The property of oxidising organic matter in water is also destroyed; this is well illustrated in Table II [22] which shows the rate of absorption of chlorine and chloramine by the Ottawa River water. The water used in this experiment contained 40 p.p.m. of colour and absorbed 9.5 p.p.m. of oxygen (30 mins. at 100° C.) . ”

“ Common salt is used daily with our food; is harmless and useful; it is known as the chloride of sodium. By analysis this compound is separated, analyzed, into chlorine and sodium. Na stands for sodium, and Cl for chlorine. Combine Cl with H. That forms hydrochloric acid, a strong poison, strong enough to dissolve marble. Cl has little attraction for O. Its chemical energies are principally exerted toward hydrogen and the metals. ”

“ The decomposition is rendered more easy and regular by mixing the salt with powdered manganese dioxide. The salt finds application in the preparation of oxygen, in the manufacture of matches, for pyrotechnic purposes, and in medicine. Sodium chlorate, NaClO3, is prepared by the electrolytic process; by passing chlorine into milk of lime and decomposing the calcium chlorate formed by sodium sulphate; or by the action of chlorine on sodium carbonate at low temperature (not above 35° C) . It is much more soluble in water than the potassium salt.
Potassium chlorate is very valuable in medicine. ”

“ In order to preserve the picture some chemical agent must be employed which shall remove or dissolve the silver chloride, but which shall not affect the chemical compound which forms the picture.
After many experiments a safe, and now cheap, [2] agent was found in hyposulphite of soda. When the print is placed in a solution of hyposulphite of soda a new compound is formed—silver sodium hyposulphite. This double salt dissolves very quickly in water, and is easily washed out of the film. ”

“ The taste and odour of chloramine is even more pungent than that of chlorine but since the introduction of the process in Ottawa no complaints have been [126] received. Owing to the reduced dosage, slight proportional fluctuations in the dosage do not produce the same variations in the amount of free chlorine which is the usual cause of complaints. A public announcement that the amount of hypochlorite has been reduced also has a psychological effect upon the consumers and tends to reduce complaints due to auto-suggestion. ”

“ Further evidence against the nascent oxygen theory of chlorine disinfection is to be found in the fact that such active oxidising agents as sodium, potassium, and hydrogen peroxides have a much lower germicidal activity than chlorine when compared on the basis of their oxygen equivalents. ”

“ The precipitated sodium chloride is filtered, and the solution of hydroxylamine distilled in order to remove methyl alcohol, and finally fractionated under reduced pressure. The free base is a colourless, odourless, crystalline solid, melting at about 30° C., and boiling at 58° C. (under a pressure of 22 mm.) . It deliquesces and oxidizes on exposure, inflames in dry chlorine and is reduced to ammonia by zinc dust. Its aqueous solution is strongly alkaline, and with acids it forms well-defined stable salts. ”

“ With oxygen it forms two oxides; with chlorine, a chloride (common salt) ; and—with bromine, iodine, fluorine, &c., bromide, iodide, fluoride, &c., all of which may be obtained by similar processes to the respective compounds of potassium, which, for the most part they resemble.
Uses. Until recently sodium has been regarded as a mere mechanical or philosophical curiosity; it has now, however, become of great practical importance, from being employed in the manufacture of the metals aluminium, magnesium, &c. ”

“ Hence, Stas gives the following method for the preparation of silver chlorate: A slow current of chlorine is caused to act on oxide of silver, suspended in water which is kept in a state of continual agitation. The shaking is continued after the supply of chlorine has been stopped, in order that the free hypochlorous acid should pass into silver hypochlorite, and the resultant solution of the hypochlorite is drawn off from the sediment of the excess of silver oxide. This solution decomposes spontaneously into silver chloride and chlorate. ”

“ 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. ”

“ The conductivity increases rapidly, [71] however, with increase of temperature and any increment due to chlorination might produce a slight appreciable effect at temperatures approaching the boiling-point of water.
Liquid chlorine does not increase the conductivity to the same extent as an equivalent quantity of hypochlorite but it increases the carbonic acid content in proportion to the dosage used.
The author investigated the action of hypochlorite on galvanised pipes in 1914 and was unable to detect any definite corrosion with normal concentrations of chlorine. ”

“ There is one substance which will produce that yellow light; it is a curious metal called sodium—a metal so soft that you can cut it with a knife, and so light that it will float on water; while, still more strange, it actually takes fire the moment it is dropped on the water. It is only in a chemical laboratory that you will be likely to meet with the actual metallic sodium, yet in other forms the [pg 326] substance is one of the most abundant in nature. Indeed, common salt is nothing but sodium closely united with a most poisonous gas, a few respirations of which would kill you. ”

“ These experiments shewed sufficiently that the whole of the chlorine had not acted upon the carbonate of soda to produce chloride of sodium, and chlorate of soda; that much was in a peculiar state of solution or union which enabled it to withstand ebullition, and yet to act freely as a bleaching or disinfecting agent; and that probably little or none had combined with the sodium, or been converted into chloric acid. To put these ideas to the test, two equal portions of the Labarraque solution were taken ”

“ Thus it is found that the muscles and skin act as the chief water depot, while such tissues as the liver, intestines or pancreas take a relatively small share in the exchange. Again, when a strong sodium chloride solution is injected a considerable part of the sodium chloride is soon found to have left the blood, and it has been shown that the chloride depot is not identical with the water depot. The lung, for instance, is found to take up relatively far more of the salt than other tissues. ”

“ The chloride of magnesium, or bittern, not only deteriorates the salt very much, but occasions a considerable loss of weight. It may, however, be most advantageously got rid of, and converted into chloride of sodium by the following simple expedient:—Let quicklime be introduced in equivalent quantity to the magnesia present, and it will precipitate this earth, and form chloride of calcium, which will immediately react upon the sulphate of soda in the mother-water, with the production of sulphate of lime and chloride of sodium. ”