IE57496B1 - Process for the preparation of a modified aqueous chlorite solution,the solution prepared by this process and the use thereof - Google Patents

Description

The invention relates to a process for the preparation of a stabilized, modified, alkalinically adjusted chlorite solution and the use of the chlorite solution obtained by this process as a biocide.

I Modified, alkalinically adjusted, aqueous chlorite solutions, particularly aqueous sodium chlorite solutions, stabilized by means of peroxy compounds, have a large number of different uses in technology and in other fields by virtue of their oxidative effect, such solutions are inter alia used for the treatment of water to be used as drinking water, as well as swimming pool water and water for industrial use for disinfection purposes. Since these solutions are not always used straight after their preparation, but are frequently only used after a long storage period, stabilizing them is very important. The use of alkaline stabilizing agents is generally known, such as for example sodium carbonate, 1 « as well as hydrogen peroxide and inorganic compounds derived therefrom, such as for example perborates. Such stabilized, modified, alkalinically adjusted chlorite solutions result from e.g. DE-C-2 728 170 and DE-C-2 730 883. -3In US Patent US-A-2 358866 an acidly adjusted stable chlorite solution is described. Stabilization is carried out by incorporating hydrogen peroxide, whereby the formation of chlorine dioxide is to be suppressed.

Stabilization is only achieved in an acid medium. Acid solutions, however, prove a disadvantage or cannot be employed at all in some fields of application. This is true for instance, when treating skin diseases.

It is also known that aqueous chlorite solutions, in which chlorine dioxide is in equilibrium with chloric acid in the acid range, can be stabilized by means of pyridine (of Holleman/Wiberg Lehrbuch der anorganischen Chemie, 47-56 edition, 1960, p.127).

Moreover, pyridine-stabilized chlorite solutions cannot be used in systems, where an additional loading with an organic substance is to be avoided, such as e.g. in drinking water and swimming pool water treatment. In addition, pyridine is a carcinogenic substance.

Stabilized and even unstabilized chlorite solutions play a particular part in the treatment of swimming pool water. Conventional, also stabilized chlorite solutions, must undergo an acid reaction course at a pH-value 43 in such a chlorine/chlorine dioxide process. For this purpose, it is necessary to use special equipment, which is not directly integrated into -4the water cycle. This applies both to the acid process and to the hypochlorous acid process, which are subordinate to the aforementioned chlorine/chlorine dioxide process. If sodium chlorite and hydrochloric acid are used, then sodium chloride and chlorine dioxide are formed therefrom according to this so-called hydrochloric acid process at the pH-value of {3. For the purposes of this reaction, reaction towers with Raschig rings are recommended in a size guaranteeing a corresponding reaction time, in order to obtain a very high conversion rate. This is also intended to ensure that on introducing the reaction product, the residual chlorite content in the swimming pool water is as low as possible, particularly max 0.1 mg/1. To prevent a redisproportioning to chlorite-chlorate, the chlorine to chlorine dioxide ratio in the swimming pool water is fixed at 10:1. In the aforementioned hypochlorous acid process, for example, a sodium chlorite solution and chlorine are metered into a water tank upstream of the water disinfection process. A reaction then takes place at a pH-value of {3, in which hypochlorous acid is formed as an intermediate stage and finally chlorine dioxide.

The thus prepared solution is then metered into the pool water as required.

In both the aforementioned processes (acid process and hypochlorous acid process), high expenditure on equipment is necessary and it must also be constantly ensured that in the acid process the hydrochloric acid -5supply is absolutely ensured and in the hypochlorous acid process that the chlorine supply is absolutely ensured, in order to avoid a disadvantageous metering of unreacted chlorite into the pool water. However, as occasionally deficiencies cannot be reliably prevented, this always constitutes a risk for the bather. In addition, the accidental mixing of commercial chlorite solutions with acids leads to explosive phenomena.

The object of the invention is therefore to so improve the aforementioned processes, that a more stable process product in an acid medium can be prepared, which can be safely and more reliably used for the treatment of water, particularly swimming pool water and which is better tolerated by the skin.

According to the invention, this problem is solved in that an aqueous, sulphate-ion-containing solution having a pH-value of <3 is mixed with a peroxy compound, which is stable therein, resulting in a concentration of peroxy compound in the end product of about 0.001 to 0.1 molar, and this solution is then mixed with the aqueous alkaline solution of a chlorite in such a quantity that a pH-value lying above 7.0 and especially between 7.5 and 8.0 is obtained. -6The peroxy compounds preferably include inorganic peroxy compounds in the form of hydrogen peroxide, persulphate, percarbonates, perborate or the peroxide of an alkali metal and alkaline earth metal. An alkali chlorite and/or an earth alkali chlorite is preferably s used as the chlorite. Particularly advantageous results are obtained, when the aqueous, sulphate-ion-containing solution has a pH-value of <1.

The peroxy compounds used for carrying out the procedure according to the invention help to stabilize the oxidation system based on the chlorite, whilst retaining the oxidative activity aimed for. The term peroxy compounds is to be understood in its widest sense and covers hydrogen peroxide (11203)/ as well as hydrogen peroxide derivatives, particularly peroxide compounds (preferably in the form of inorganic compounds), which contain the ion 032- as a ligand, or in which -0- is replaced by -0-0-, peroxides and peracids as well as their salts. The peroxy compounds include, in particular, inorganic peroxy acids and, as already mentioned above, their salts. For the purpose of the invention, oxy acids of the perchloric acid type including their salts should be considered. Amongst the salts of the above mentioned acids, sodium, potassium and calcium compounds take precedence. -7The stabilization by peroxides preferably takes place by barium or sodium peroxide.

For the case where the stabilized, modified chlorite solution is used in systems where additionally introduced, organic substances are unobjectionable, the aforementioned peroxy compounds can also be organic. Within the scope of the given teaching, the Expert will be able to find further stabilizing peroxy compounds, which are suitable for the purposes of the invention.

You will also be able to readily determine the appropriate concentration of the stabilizing peroxy compound. It is surprising that preferably relatively small peroxy compound concentrations are adequate for the purposes of the invention and when using the stabilized products, particularly favourable effects are obtained.

This more particularly applies with a 0.001 to 0.01 molar concentration of the peroxy compound in the greenish finished solution. With respect to the objectives of the invention, higher concentrations regularly lead to no advantages and frequently exclude the sought effects, or do not lead to them being obtained in the sought manner. Moreover, the small stabilizing peroxy compound quantity reguired by the invention means that there is substantially no cost increase. -8In the process according to the invention, a suitable stabilizing peroxy compound is converted into a weak acid solution. This solution preferably has a pHvalue of 43, whilst is particularly advantageous. Acidification can take place by means of mineral acids such as hydrochloric acid, sulphuric acid, etc, but also by adding hydrogen compounds, i.e., acid, organic salts, particularly alkali metal or alkaline earth salts, or in the form of a combination of the above compounds. Preference is given to sodium, potassium and calcium salts, particularly in the form of their hydrogen sulphates.

When selecting the acidifying compounds, account must also be taken of the subsequent use of the product according to the invention. It is generally particularly advantageous if the sulphate ions are formed with sulphuric acid. For example, it is possible to proceed in such a way that a sulphate is added and that the desired pH-value is obtained with another acid. Fundamentally, it is possible to use hydrochloric acid. However, compared with the use of sulphuric acid, this leads to a certain disadvantage in that, despite the described interaction with chlorite, excessive chloride quantities prematurely lead to the formation of chlorine dioxide and not only when this is required, and this disturbs the desired equilibrium system, accompanied by gassing out and consequently to chlorine dioxide removal. -9This leads to an undesired weakening of the system in the sense of the invention.

Into the above-described, weak acid aqueous solution of the peroxy compound is metered an aqueous chlorite solution and its concentration is not decisive. Thus, it can in particular be a commercial aqueous alkali metal and/or alkaline earth chlorite solution, particularly a sodium and/or calcium chlorite solution. The pH-value of the commercial alkali metal chlorite solution is generally above 12. Solutions of this type regularly contain approximately 300 g/1. However, it is obviously possible to drop below this value. As according to the invention, regularly a strong concentrated, stabilized and modified chlorite solution is sought, it is obvious to use a strong, concentration chlorite solution as the starting material. The metering in of the starting chlorite solution preferably takes place with stirring until the original partly gassing, dark brown solution has assumed a greenish yellow or greenish shade. This is generally the case when the pHvalue is above 7. Preference is given to a pH-value of approximately 7 to 8 and particularly 7.5 to 8.

It has surprisingly been found that in the process according to the invention, the peroxy compound -10quantity can be drastically reduced if a watersoluble phosphate, e.g.sodium metapolyphosphate is incorporated in a small quantity into the finished solution.

In the case of the process according to the invention, an excessive reaction in the form of explosive phenomena can occur if the aqueous starting solutions used only have a limited carbonate hardness, or when demineralized water is involved. In such cases, it is advisable to work under an inert gas atomosphere. Preferably, prior to the metering in of the chlorite solution, a generally adequate small quantity of a hydrogen carbonate, e.g. sodium hydrogen carbonate, is metered into the acid aqueous solution. In the case of aqueous starting solutions with an average or high carbonate hardness, such a measure is not generally necessary, because a type of inert gas layer of carbon dioxide is formed between the slightly gassing chlorine dioxide and the air. Thus, no explosive air/chlorine dioxide mixture can form. In the case of an air to chlorine dioxide ratio of approximately 10:1, such a mixture tends towards an explosive decomposition of the chlorine dioxide into chlorine and oxygen.

The stabilized modified chlorite solution according to the invention has an extremely favourable storage period of several months, without there being any significant reduction to the desired oxidative -11action. After some time, there is a yellow-brown colouring as a result of the proportionately released chlorine dioxide, but this does not significantly impair the desired activity. If the released chlorine dioxide proportion is removed from the agueous solution, e.g. by extraction by shaking, with carbon tetrachloride then after a short time the desired greenish colouring of the clear agueous solution reappears. This means that in the sense of an equilibrium reaction, the chlorite solution always re-forms chlorine dioxide during the removal thereof. This occurs even at high dilution, also e.g. when the chlorine dioxide formed has used up its oxidative action through the influence of reducing substances, particularly organic substances.

Unlike in the conventional prior art chlorite solutions, in the stabilized modified chlorite solution according to the invention, there is a positive redox potential between approximately 450 and 500 mV, as a function of the light action. It is important for the subsequent action, as well as for the action ranges described hereinafter that a stabilizing effect is obtained with a minimum, controllable quantity of a peroxy compound. As the stabilizing action of peroxy compounds with respect to chlorine dioxide or chlorite solutions is highly pH-dependent according to the known procedure, a relatively large amount of peroxy compound must be added to an acid chloride dioxide solution to be stabilized. This also applies for stabilization in the alkaline range.

. In.this case, large peroxy compound excesses must be added, because this compound decomposes strongly in the alkaline -12range. Following pH-reduction, it is no longer possible to establish what peroxy proportions are still present in the finished solution. In principle, larger peroxy compound proportions lead to an unacceptable interference to the subsequent use of the two last-described, prior art chlorite solutions in the aforementioned use ranges. In addition, a chlorite solution in specific use ranges should as far as possible be roughly pH-neutral which, unlike in the case of the chlorite solution according to the invention, does not apply for the aforementioned prior art solutions. The technological background of this will be made even clearer during the following comments with respect to the prior art.

For example, the following procedure is used in the process according to the invention. A very small quantity of a peroxy compound is added to an acid (particularly sulphuric acid) solution, whose pH-value is preferably -1, so that there is an approximately 0.0022 mol peroxy compound concentration in the finished chlorite solution. This finished solution contains approximately lOOg of chlorine dioxide per litre. In ordeir to stabilize such a chlorine dioxide quantity with minimum amounts of peroxy compounds in the pHrange of 7 to 8, the following procedure is adopted. Approximately 6kg of a bubbled sodium hydrogen sulphate is incorporated, accompanied by stirring, into approximately 200 litres of tap water with a carbonate hardness of 18. Approximately 100ml of a 30% ^2θ2 so^u^1on 1S added to the aforementioned solution. After stirring for -13roughly 10 minutes, 200 litres of an approximately 30% sodium chlorite solution is added to the ' aforementioned solution over a period of roughly 10 minutes until the neutral point is reached. In the still strong acid phase, the small peroxy compound quantity is adequate to keep the still small chlorine dioxide proportion stable. As with rising pH-value, the stabilizing nature of the peroxy compound with respect to chlorine dioxide increases, the processes take place in accordance with a self-controlling equivalent. Possibly a complex compound of chlorine dioxide forms where, unlike in other known processes, the peroxy compound does not act in the chemical reaction mechanism (such as e.g. in accordance with the equation 2 C102 + 2 H0~ + HgOg-* 2 C102‘ + 2 H20 4- 02). On reaching a pH-value of approximately 7, the previously dark brown solution changes to lime green and has an oxidation potential of approximately 300 mV. If this solution is exposed to direct or indirect daylight for 24 hours, after a certain time a so-called kick reaction occurs and the solution assumes a golden yellow colour.

This is linked with a potential jump to approximately +450 to 550 mV.

If the solution prepared in the aforementioned manner is now treated with carbon tetrachloride, the free chlorine dioxide proportion is consequently extracted by shaking, which means that the free chlorine dioxide passes into the carbon tetrachloride phase, -.14accompanied by yellow colouring, whilst the aqueous phase is pale. However, after a short time, it is found that chlorine dioxide has been reintroduced into the remaining aqueous phase (yellow colouring).

This procedure can be repeated until the aqueous phase is exhausted. If the stabilized chlorite solution according to the invention is added to warm water, there is a slight ozone odour, apart from the typical chlorine-like odour.

If the solution according to the invention is highly diluted with water, then the equilibrium thereof is displaced in the direction of the chlorine dioxide, which still applies in the pH-range of approximately 7 to 8.5.

If the stabilized, modified chlorite solution according to the invention is used, then the desired action of the neutral or weak alkaline solution by acidification or accompanied by the action of a random reactant, e.g. chlorine, accompanied by the release of chlorine dioxide, takes place in such a way that under normal conditions a yellowish-reddish gas is provided. Due to the presence of chlorine, particularly with an elevated chloride proportion, or mineral acids in a treated aqueous system, the chlorine dioxide formation reaction takes place in privileged manner compared with the undesired chlorate reaction. The desired reaction sequence is not disturbed, even on adding strong mineral acids in -15high concentration, which is not the case with the known chlorite solutions. Under the action of strong mineral acids, these known solutions still exhibit the aforementioned explosive phenomena.

There are also cases where the chlorite solution according to the invention is subject to distabi1ization, in that the system to be treated contains a reactant for the peroxy compound present in small quantities and reduces the latter and consequently eliminates the stabilization of the chlorite solution. Such a reactant can e.g. be the peroxidases and catalases present in germ cells, i.e. enzymes of the animal and vegetable metabolism belonging to the group of peroxidoreductases. The action thereof leads to the spontaneous release of chlorine dioxide. As a result of this fact, the stabilized, modified chlorite solution gives high selectivity when used biocidally in small quantities.

The chlorite solution according to the invention, particularly in the form of a sodium chlorite solution can be used particularly advantageously in water treatment. This mainly refers to the treatment of drinking water, water for industrial use and swimming pool water for disinfecting purposes. This disinfection preferably takes place accompanied by the simultaneous use of chlorine, so that chlorine dioxide, which is highly effective for disinfection purposes, is formed. For example, a sodium chlorite solution with approximately 300g of sodium chlorite -16per litre is used for preparing the stabilized chlorite solution. The finished solution generally contains 8 to 15% by weight of chlorine dioxide, the range 10 to 12% by weight as a rule being particularly advantageous all points considered. It is also possible to add to this solution various other constituents, such as sodium chloride, sodium sulphate and sodium chlorate. The sodium chlorite solution according to the invention can be so adjusted by dilution, that it satisfies the KOK (coordination committee for swimming pool construction and operation) guidelines, which stipulate a residual chlorite content in swimming pool water of max. 0.3 mg/1 of pool water. It then also satisfies the DIN draft 19643 of max. 0.1 mg/1.

The above comment also applies to other chlorite solutions, such as other alkali metal and alkaline earth chlorite solutions.

The chlorite solution according to the invention is particularly advantageous in the treatment of swimming pool water, as will be described in greater detail hereinafter.

It is firstly stressed that the explosive phenomena referred to hereinbefore in connection with known processes are eliminated when the chlorite solution according to the invention is used. Even on mixing with concentrated sulphuric acid, an explosion cannot occur. Its particular suitability for the treatment or conditioning of swimming pool water has been proved by an expert opinion of the -17Gelsenkirchen Institute of Hygiene. In connection with an equivalence proof, it was found that the solution according to the invention behaves quite differently to commercial chlorite solutions or solutions stabilized in some other way. In the tests performed by the Institute of Hygiene, the solution according to the invention was metered by means of a fine metering pump via an inoculation point between the flocculation inoculation point and the filter t directly into the pool water circuit (pH-value of 7.5). All the water samples taken revealed chlorine dioxide, but not the chlorite (C10_2) to be avoided.

It is also important in this connection that even very small amounts of peroxy compounds have a disturbing action in chlorinated pool water. With respect to strong oxidizing agents, such as chlorine, peroxides assume a reductive character. Thus, they considerably reduce the oxidation potential which, in swimming pool water, plays an important part for the germ killing rate. Nowadays, in many swimming ΐ pools, the addition of disinfectant is automatically controlled via this parameter. In the case of an artificial change (reduction) of the oxidation potential, vast quantities of e.g. chlorine would pass uncontrolled into the pool water. This risk is largely eliminated by the use of the chlorite solution according to the invention. The small peroxy compound quantities introduced into the pool circuit are of an order of magnitude which can just -18be eliminated by e.g. finely divided metal impurities on the filter or peroxidases occurring in certain germs.

As a result of the chlorine dioxide spontaneously selectively released in this way in contaminated filter material, additional phenomena occur which do not take place in conventional chlorine/chlorine dioxide processes.

The aforementioned equivalence proof revealed that the time between the necessary filter backwashes after differential pressure could be doubled or the pool water quanitiy required for backwashing could be reduced by half. It was also found that the filter treated with the solution according to the invention I can discharge double the pollutant quantity in half the time. This is possibly due to a better flocculation of the organic/inorganic loading substances and to a prevention of the adhering over of the filter material. This permits an easier, faster discharge of the collected pollutant particle. The chlorite solution according to the invention also prevents strong contamination of highly loaded filters. Thus, in the specifically adjusted manner it acts as a filter aid.

Its described use leads to considerable savings in fresh water, waste water, heating and treatment costs.

The following occurred in connection with the Bockum/ Hovel, Hamm indoor swimming pool used for the equivalence proof. During the normal treatment, flocculation filtering - chlorination, the necessary amount of fresh water per bather is 0.11 m , whilst when using the chlorite solution according to the invention on -193 average 0.03m of fresh water are required for each bather. Thus, the saving for each bather is 0.08m .

Thus, the following statements can be made in connection with the use of the chlorite solution according to the invention for the treatment of swimming pool water. This solution can be directly added to the chlorinated swimming pool water, chlorine dioxide being directly formed in the pHrange of approximately 7 to 7.8. However, the treatment with the solution according to the invention preferably takes place between the flocculation and the filtering stages. There can e.g. be approximately 24ml of a roughly 10% by weight chlorite solution for approximately 180 m of circulated swimming pool water. The 100% conversion to chlorine dioxide takes place so rapidly that in the case of crude water metering, no chlorite but only chlorine dioxide could be detected as far as the pure water was concerned. The water quality obtained is superior to that of known processes (acid or hypochlorous acid proces ses). As shown, the treatment process operating with the chlorite solution according to the invention is very inexpen si ve.

The stabilized, modified chlorite solutions according to the invention also have further uses. Thus , it has been found that in particular dilute chlorite solutions according to the invention excellent biocical actions in the widest sense. This more particularly applies to a dilute sodium chlorite solution, preferably with an approximately 0.1 to 0.5*by weight concentration. It can be used for -20hygienic, disinfecting personal hygiene, e.g. for foot care in swimming pools, saunas, etc., particularly in the treatment of perspiring feet· It Is also very suitable In the case of externally treatable skin diseases and Irritations· particularly skin eruptions* psoriasis* eczema* lupus* hymenomycetes or generally In Inflammatory skin diseases* which are caused by bacteria and protozoa, viruses or fungi (candidamycosis* trlchophytia, pityriasis* herpes* etc). The agent according to the Invention and particularly the sodium chlorite solution .can also be used for treating skin diseases in the throat or mouth* such as bleeding of the gums. Thus* these agents are a type of medicament.

In addition* the chlorite solution according to the invention can be generally considered as a cosmetic* which can be added in small concentrations to the bath water when bathing. Certain of the aforementioned uses will be described in greater detail hereinafter.

In pharmaceutical fields* it has been found that the solution according to the invention is compatible with the skin to a high degree. It can even be supplied in concentrated form to the healthy skin* without allergic reactions being detected. The skin generally acts highly allergically to normal chlorite solutions of the same concentration. It was in fact found that a dilute chlorite solution according to the invention led to surprising improvements to allergies. In dilutions of the concentrated solution to water of 1:10, there were even found to be spectacular antimycotic actions. The chlorite solution according to the invention also proved to be effective in healing severe neurodemititls* which had in part persisted for some years. -21However, the solution must he highly diluted here, e.g. 20 to 30ml per both with a slow Increase up to the limit of the compatibility of the particular patient.

A very surprising phenomenon occurs In the treatment of psoriasis, with baths every day or every two days (approximately lOOml/bath, whilst excluding other additives) the scales were detached with roughly 80% of the patients after the first few baths and without any mechanical action and itching generally rapidly decreased. The raised skin parts became flatter and the dark red colouring turned pale pink. Following a generally occurring stagnation phase of approximately 2 to 3 months, the previously attached skin parts normalized. A function Is possibly played during this treatment by the successive giving off of small ozone quantities during bathing (metabolism regulation via the large-area skin contact). Persistent perspiration odours were eliminated by bathing the body and feet. Other useful uses are mouthwashes with a 3b solution, which eliminates bleeding of the gums.

A further surprising action was found during the treatment of diabetic gangrene (leg sores). In one case, a wound as wide as the thumb and about 7cm long healed on bathing with a dilute sodium chlorite solution according to the invention (dilution with water in ratio 1:100) following treatment for about 8 weeks.

Finally, chlorite solutions according to the invention and preferably the sodium chlorite solution, can be used industrially, e.g. in combatting slime in -22water systems. This more particularly applies to the conservation of drinking water In various containers or tanks, particularly on ships. Such a solution can in such cases be used very effectively and without application problems.

The drinking water treated with the solution according to the Invention remained germ-free for several months In closed containers. Vith the ppm range quantities used, there was no deterioration to the taste of the water. There were also no toxicological objections.

The oxidizing effect of the chlorite solutions according to the invention can e.g. be used in wider technical fields, e.g. in the combination with mineral acids or chlorine. Thus, they can be used In the production of cellulose, the bleaching of oils, fats, waxes and leather and for disinfecting or deodorizing evil-smelling waste and sewage. A special application Is the stagewise bleaching of pulp.

In summarizing, it can be stated that the stabilized, modified, aqueous chlorite solution according to the invention can be advantageously used wherever it is to lead to an oxidative action, particularly due to the formation of chlorine dioxides. This can be dead matter of organic, particularly reducing substances, as well as living organisms, such as microorganisms, fungi and the like. Thus, the chlorite solution according to the Invention can he considered in the widest sense as a biocidally active -23agent with absolute skin compatibility, i.e. it can be used as an insecticide, fungicide, herbicide, etc, where hitherto commercial sodium chlorite solutions have either proved unsuitable or have only had a limited success. A particular advantage of the chlorite solution according to the invention is that it generally permits a 100% conversion of the chlorite into chlorine dioxide in a wide pH-range. In addition, the solution according to the invention can be prepared simply and easily and without the need for a great deal of equipment, in that e.g. the acid solution (preferably with a pH-value The invention is further illustrated hereinafter by means of an example: Example 0.5g of a 30% by weight hydrogen peroxide solution is added to 1 litre of water (carbonate hardness: 18°) with a pH-value of 0.5. 0.91 of a commercial sodium chlorite solution (approximately 300g of sodium chloride /litre) is added to this solution, accompanied by adequate stirring. The solution has a brown colouring and on exceeding the pH-value of 7 and following the stabilization reaction changes to -24a light, lime green colour. A pH-value of approximately 7.5 is obtained in the solution, which gives a 100% conversion to chlorine dioxide when treating the water of an indoor swimming pool. Conversion takes place so quickly that as far as the pure water is concerned, chlorite was never detected, although small amounts of chlorine dioxide were found. The water quality is significantly improved. The fresh water addition per bather can be reduced to 20%.

The aqueous solution prepared in the aforementioned manner, inter alia has an excellent action in the treatment of psoriasis and hymenomycetes when used in a 0.1 to 0.5% by weight concentration.

Claims (9)

Claims

1. A method for the production of a modified, alkalinically-adjusted, aqueous chlorite solution which is stabilised by a peroxy compound, characterised in that an aqueous, sulphate-ioncontaining solution having a pH-value 43 is mixed with a peroxy compound which is stable therein, which results in a concentration of peroxy compound in the end product of about 0.001 to 0.1 molar, and this solution is then mixed with the aqueous alkaline solution of a chlorite in a quantity.such that a pH-value of above 7.0, especially between 7.5 and 8.0 is obtained.

2. A method according to Claim 1, characterised in that an inorganic peroxy compound in the form of hydrogen peroxide, a persulphate, percarbonate, perborate, or of a peroxide of an alkali metal or earth alkali metal is used as peroxy compound.

3. A method according to one of Claims 1 or 2, characterised in that an alkali chlorite and/or an earth alkali chlorite is used as chloride.

4. A method according to Claims 1-3, characterised in the that/agueous, sulphate-ion-containing solution has a pH-value <1. -265. A method according to Claims 1-5, characterised in that mineralised water is used for the production of the aqueous, sulphate-ion-containing solution. 6. A method according to Claims 1-5, characterised in

5. That a water-soluble phosphate is added to the end product.

6. 7. The use of aqueous chlorite solution obtained by the method according to Claims 1-6 as a biocide, especially for the external treatment of skin 10 diseases and irritations, and for water purification.

7. 8. A method substantially as hereinbefore described i with reference to the Examples.

8.

9. An aqueous chlorite solution whenever prepared by a 15 method as claimed in any of Claims 1 to 6 or 8.