CA1074252A - Spray sanitizing system with electrolytic generator - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A spray sanitizing system for creating a continuous supply of sanitizing liquid is provided with a hand operable wand having a liquid discharge nozzle and a portable central generator unit which includes an electrolytic cell for instantaneously generating a relatively low pH bacter-icidal solution containing nascent chlorine which is mainly in the form of hypochlorous acid.

Description

, , 1()'~ ' lhe p~cse~t invel)~it)n rcla~es ~n thc saniti-,in~, a~ld s~crilizin~ of the sur~aces of objects and, more particularly~ to ~ ~ys~em and me~noa ror als mrcc~ln~ D~cLeri~ iaaen surrac~s DY
spraying the objects wi~h a sanitizing solution.
In ~ood processing plants, bottling plants, dairies and the like, it is a constant requirement that sanitary condi-tions be maintained. One important sanitizing requirement is the disinfecting of the surfaces of physical objects about the plant by the use of bactericidal sanitizing methods. Tlle systems and methods which must be employed, particularly in food processing installations, must be safe and ~on-toxic when they are being used, and also must be safe and l~on-toxic in storage prior to use, and must furthermore leave no unsafe or toxic resins.
Several bactericidal nlethods have been ernployed in the prior art, One common method of ~he prior art is to wash all physical objects including walls and major items of.equipmen~
with a bactericidal solution containing bactericidal substances such as quaternary ammonia or chlorine. Chlorine solutions, for ; example, have been found to be fairly efective in killing bacteri a in such cases. However, low p~ chlorine solutions which are the most effective bactericides are so highly unstable and have such a limited shelf life that the storage and use of them as effectiv~
bactericid~s has heretofore been highly impractical. ~igh pH
. solutions, on the other hand, in which chlorine is largely in the form of sodium or calcium hypochlorite, have a somewhat longer shelf life, but are less effective bactericides than the 1(~74~2 low pH solutions in which the chlorine is largely in the form of ~ypochlorous acid. To maintain high pH solutions in which the chlorine is in the more stable form, it is necessary that additives such as sodium hydroxide be added to the solution Such additives, in addition to decreasing the bactericidal effectiveness of the solution, create an additional hazard in that a toxic and irritative solution is formed which leaves a toxic and irritative residue on the surfaces which are washed with the solution and requires that the subsequent washing of these surfaces be undertaken in order to remove this residue. Other additives, for example some used as stabilizers for calcium hypochlorite, form dangerously flammable compounds if not handled or stored properly. Since the most practical way of disinfecting the facilities in the food processing industry has been to wash the facility with the spray of the disinfecting solution, which solution has been purchased in bottle form and stored for at least a short period of time or premixed prior to use from powdered chemicals, these disadvantages have been inherent when such dis-infecting methods have been used in the prior art.
The present invention overcomes the disadvantages of the prior art by utilizing the high bactericidal effectiveness of relatively low pH
chlorine solutions while avoiding the problems inherent in storing and preserving the solution prior to use, and while eliminating the toxic irritating and hazardous effects of certain solution additives.
The present invention provides a method and apparatus for contin-uously generating a bactericidal solution in which the predominant bacteri-cidal constituent is hypochlorous acid. To this end the invention contemplates the formation of a brine solution to which an acid, preferably acetic acid, and water are added so that the resultant solution has a pH of approximately 6. That solution, when immediately electrolyzed, results in the production of chlorine in a bactericidal form of which 95-98% is hypochlorous acid.
According to one aspect of the invention there is provided a method ' ~I
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for producing the method of creating a bactericidal solution compris mg the steps of; mixing sodium cnloride, an acid and sufficient waber to prcvide a solution having a pH of approximately 6, and electrolyzing the solution to generate nascent chlorine ~hich is mainly in the form of hypochlorous acid.
The lcwering of the pH of the solution to approxlmately 6 is extremely im~ortant to the efficacy of the subsequently electrolyzed solution.
The following table illustrates the dramatic change in the ratio of hypcchlor-~3a-~ ,:

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ous acid to other and less efficacious chlorine containing constituents: -pH Value% available CL2 in the form of Hypochlorous Acid at 6.o98% of total free CL2 ;~ up to 6.795% of total free CL2 at 7.080% of total free CL2 at 8.o21% of total free CL2 at g.o2.7% of total free CL2 at 10 0.3% of total free CL2 While the lowering of the pH below 6 does not adversely affect the cidal prop0rties of the solution, the solution tends to become ~uite corrosive and hence less desirable.
Further, it has been determined that low pH nascent chlorine~ in the form of hypochlorous acid, is up to three times as effective or has three times the killlrate of nascent chlorine as a hypochlorite.
Also disclosed herein is a method and apparatus for continuously forming the desired low pH cidal solution, including the supplying of metered amounts of glacial acetic acid to a brine solution and mixing the resultant solution with metered amounts of water to form the solution to be electrolyzed In the process it is contemplated that the amount of acetic acid in relation to the other constituents will have to be varied to account for differing pH of the incoming tap water normally employed in the process.
Further, there is disclosed an industrial system and method for disinfecting the surfaces of objects, particularly in food plants and other areas where high bactericidal effectiveness is required but where toxicity must be completely avoided. The problems of the prior art are overcome by providing a disinfecting system in which a continuous stream of bactericidal ; sanitizing liquid is sprayed upon objects to be disinfected, and in which the bactericidal effect of the sanitizing solution is enhanced by generating nascent or instant chlorine in a relatively low pH solution, immediately Xl -4-1~ .

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before the solution is sprayed upon the objects which are to be disinfected.
By generating this nascent chlorine in a relatively low pH solution, in its most effective but least stable form, and then spraying it in a continuous -4a-~,., ~0~4Z~ -washing stream directly upon the surfaces of objects to be disinfected immediately after the . -.

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solution is generated, and before the solution is able to deteriorate to a less effective level, results in a greatly increased bactericidal effectiveness over the systems and methods of the prior art.
In addition to the high bactericidal effecti~eness of the present invention over the prior art, and the advantages provided in the reduced toxicity and irritability to living tissue which the present invention provides, it has been found that the materials required cost only a small fraction of the cost of materials used in common methods of the prior art.
There are several other advantages which the present invention provides, particularly when compared with systems of the prior art in which the high pH hypochlorite solution is maintained by the addition of, for example, caustic lye. Nascent chlorine solutions can be detected by smell only at concentrations that are many times higher than the concentrations of these prior art solutions. The same applies to detection by taste. Furthermore, the stable hypochlorite solutions will irritate the eyes and will bleach certain colors at far lower concentrations than will nascent chlorine.
Purthermore, the nascent chlorine is believed to be far superior to the stable hypochlorite solution in its ability to eliminate odors.
While prior art systems have been devised for utilizing the electrolytic generation of chlorine for disinfecting and sanitizing purposes, the advantages of utilizing nascent electrolytically generated chlorine for a spray solution, in industrially usable quantities, to sanitize the surfaces of objects has not been realized or appreciated.
For example, electrolytic chlorine systems ha~e been proposed for disinfecting a fluid or water supply by electrolytically generating chlorine in the solution which is to be disinfected to kill bacteria carried by the fluid. One such application has been in the swimming pool disinfecting area. Another application has been in deodorizing air, an area in which the decomposition and deterioration of the solution in which the chlorine is generated results in a dispersing of the bactericidal -"` 1074252 :~

chlorine into the atmosphere which is to be disinfected.
The present invention, unlike the systems of the prior art, enables bringing the chlorinated solution, while in its most effective bactericidal form, on~o the surfaces of objects to more effectively and completely disinfect the objects than has heretofore been realized, while maintaining greater safety but far lower toxicity and at a lower cost than has been realized in the prior art.
More specifically, it has been an objective of the invention to provide a process for disinfecting meat carcasses by spraying or washing the carcass with the low pH solution of the present invention at a concentration from twenty-five to about two hundred parts per million.
In the meat processing industry, the meat carcass after slaughtering is highly contaminated on its surface with bacteria. Surface contamination has a considerable shelf life shortening effect on the meat, for in the cutting of the meat into its component parts and grinding into ground beef and the like, the surface bacteria are driven from the surface of the meat into interior portions of the meat where they multiply resulting in early spoilage of the meat. Numbers of attempts to solve this problem have been made but have been ineffective. Of the attempts made, perhaps the one which approaches a practical process is that of washiDg the meat carcass with a commercial high pH hypochlorite of the type described above. This process, however, has been effective in eliminating only 90% of the bacteria. The remaining 10%, having the capability of migrating or being forced onto interior surfaces of the meat and having the capability of multiplying under conditions of storage, still give rise to demonstrable spoilage. It has been found that by washing the surface of the meat with the solution produced in accordance with the present invention, the bacteria are entirely or substantially entirely eliminated from the surface of the meat;
that is to say, the resulting bacteria are too few to count, indicating that ~he process is at least 9g.99% effective.

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These and o~her objectives and advantages of the pr~sen~
invention ~ill be more readily apparent from the following detailed description of the drawings illustrating an electrolytic spray sanitizing system and method according to principles of the present invention.
Figure 1 is a hybrid block, plumbing, and schematic diagram of an electrolytic spray sanitizing system embodying principles of the present invention.
Figure 2 is a perspective view of a portable unit housing the disinfecting solution generating components, and of the portable wand of the system of Figure 1.
Figure 3 is a cross-sectional view of an electrolytic cell suitable for use in the system of Figure 1.
Referring to Figure 1, one preferred embodiment of a system according to the present invention operates to spray a sanitizing liquid in the form of a continuous spray 1~ directly upon the bacteria laden surfaces of objects to be disinfected, such as the walls and floors ` of the building structure 11 in, for example, food processing plants .~ and the like, or upon the surfaces of other objects 12 such as machinery, furniture, or other equipment in such facilities.
The sanitizing system includes two independently movable parts which can be better seen by reference to Figure 2. These parts are the portable sanitizing solution generating unit 20 and the spray wand 30. The unit 20 includes a high grade stainless steel cabinet 21 mounted on casters 22 so that it can be rolled freely about a plant.
: Mounted on the front of the unit 20 are a power on-off switch 23, a power on indicator light 24, a chlorine solution output meter 25, and an operating instruction plate 26, all arranged on an operator panel 27. The unit 20 also includes a power line cord 28 which is connectable either to a 220 volt AC or a 110 volt AC power line, depending on the internal wiring of the unit 20.
The unit is provited with a fluid inlet port 29 connectable to a conventional tap water outlet of cold water, preferably supplied ;

0';~2~2 at a pressure of from 40 to 65 psi. T~e unit is further provided with two outlet ports for dispensing sanitizing fluids. These ports include a primary outlet port 31 and a bulk outlet port 33. When the system is operating according to principles of ~he present invention, sanitizing solution will be emitted through the primary outlet port 31 and conducsed through a hose 32 to the wand inlet port 35.
The unit 20 is also provided with an electri al connector 36 which connects through a control cable 37 to a trigger toggle switch 38 carried by the want 30. The switch 38 provides a means for cont~olling operation of the generator unit 20 from the hand held want 30 to selectively control -the output of spray solution. The switch 38 is a three-position switch having an "OFF" position, a "sanitizing solution ON"
position which causes the generation of sanitizing solution and the pumping of the solution to the wand 30, and a "flush ON" position in which unchlorinatèd water is communicated through the central unit and to the wand to flush the system.
The wand 30 is provided with a pistol grip-type handle 41, a fluid discharge nozzle 42, and a rigid tubular contuit 43 which communicates fluid from the wand inlet poTt 35 to the nozzle 42.
Referring again to Figure 1, the internal and operative details of the wand assembly 30 and the central unit 20 are ; illustrated. The central unit 20 includes two basic sub-systems. the solution generating or fluid handling sub-system 50, and the electrical control system 110.
The solution generating system 50 includes a brine tank 52 in which a saline solution is prepared. This tank has a removable lid 53 fastened to the tank 52 by bolts 54.

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The lid 53 is removable so that salt 55 can be daposited in the tank, and so that the tank can be cleaned periodically.
A level of water 56 is maintained in the tank 52 and the quantity of salt 55 is maintained at such a level that a saturated saline solution is formed in the water 56.
The tank 55 is provided with an outlet pipe 57 which connects to the input of a positive displacement pump 58 which is driven by a motor 59. The pump 58 is a diaphragm type pump having a variable displacement which is controlled by a cam on the drive shaft 61 of the motor 59. The outlet of the pump 58 is connected through a check valve 62 to a "T" 63 which has an outlet connected to the inlet 66 at the bottom of the electrolytic cell 70.
The apparatus includes a system for supplying metered amounts of acid, preferably 85% glacial acetic acid, into the saline solution to lower its pH. If the tap water and hence the saline solution is at a pH of 7, then 2 oz. of acid for each gallon of water are required to achieve the desired pH level.
The acid is contained in a supply 75 connected through a line 76 which includes a pump 77 to the tank 52. Tank 52 is also supplied with fresh make-up water from the inlet port 29 via a line 78 which contains a throttle valve 79 and a flow switch 80. A float valve 81 connected to the line 78 detects the demand for additional solution as, for example, when the solution level drops by two gallons ant permits water from the port 29 to flow through line 78 to the tank 52. The throttle val~e is set to meter the fresh water at two gallons per minute.
The flow of water closes switch 80 causing pump 77 to operate to supply acid to the tank. The pump has 1074;~SZ

a variable setting permitting the operator to meter the flow of acid to the tank in accordance with the flow of water and its pH. For example, if the water is at 7 pH, she pump would be set for 4 oz. per minute ~o result in

2 oz. of acid per gallon of make-up solution.
The clear water inlet 29 of the unit 20 is also connected through a solenoid controlled check valve 71 operated by a solenoid 72 and through a manually controlled needle valve 73 ant a check valve 74 to the other input of the "T" 63. At the "T" 63, clear water from the input 29 is mixed with the saline solution from the tank 52 in . ratios which are controlled by the combined settings of the cam on the pump motor input shaft 61 and the needle valve 73.
The combined solution enters the cell 70 at the .
.. cell input 66 and flows upwardly through the cell where the solution is chlorinated in a conventional manner in ; which the electrolytic reaction causes chlorine gas to be formed and to combine with the other constituents of the solution to form principally hypochlorous acid (HOCl), certain other compounds such as sodium hypochlorite (NaOCl), : and certain active free radicals, along with other byproducts of the reaction. The chlorinated solution, now at a p~l -of 6 - 0.1, is emitted from the cell 70 at the outlet 69, into a "T" 68. The "T" 68 provides alternative outlets for the solution from the cell through a pair of manually controlled gate valves 64 and 65. The valve 65 controls the emission of bulk solution at the outlet 33 of the unit 20 in the event that it is wanted for use in sanitizing :; :

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processes other than the spraying of physical objects.
The gate valve 64 controls solution to the outlet 31 which -~
connects to the hose 32 to communicate the electrolytically generated chlorinated sanitizing solution to the wand 30.
This solution, when flowing, enters the wand 30 at the inlet 35 and is communicated through $he tube 43 to the nozzle 42. All fluid fittings of the system are preferably constructed of either polyvinyl chloride or stainless steel to insure high corrosion resistance.
The details of the cell 70 will be better understood by reference to Figure 3. The cell 70 includes a cylindrical cell body 67 made of a non-corrosive metal or other non-corrosive material. The body is provided with an inlet 66 at the bottom ent 82 thereof and, at its upper end, is providet with a flange 83. The cell head 85, made of electrically non-conductive material, is secured tightly to the top of the flange 83 by bolts 87 in such a way as to seal the interior 86 of the cell 70. The upper -10~ 5Z

surface of the flange carries an O-ring 90 to effect a seal between the head 85 and the cell body 67. The cell head 85 is provided with an outlet passage 89 which communicates between an interior opening 88 at the center of the cell head 85 at a point between the electrodes and the cell outlet port 69.
The cell 70 is provided with a pair of electrodes including an anode assembly 91 and a cathode assembly 92. The anode 91 is preferably constructed of a noble metal material such as platinum or platinum alloy. It may be constructed either of a solid noble metal alloy or consist of a noble metal plated or larninated material. Other materials may also be suitable . ~, .
for some applications such as carbon or lead dioxide. Each type has certain disadvantages; the preferred noble metal anodes, while the most desirable, are the most expensive. Carbon anodes deteriorate rapidly to the point of adversely affecting the efficiency of the cell. Lead dioxide is moderately acceptable but it must be insured that the lead does not contaminate food ; processing or other like areas. The cathode 92 need not be constructed of a noble metal but should be constructed of a non-corrosive material. Several commercially available titanium and nickel alloys are suitable for this purpose. The electrode assemblies 91 and 92 include the lower immersible portions 93 and upper support portions 94 which extend through the cell head 85. The support portions 94 are adapted to secure the electrodes 91 and 92 to the cell head 85 and are provided with threaded ends . ' .

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by which they may be tightened to the head 85 through the use of the nut and washer assemblies 96. A6Ove the nut and washer assemblies 96 on the electrode support portions 94 are provided other means, such as additional nuts and washers 97, to enable the electrodés to be connected to appropriate wire conductors. A pair of tapered neoprene washers 99 surround the support portions 94 beneath the nut and washer assemblies 96 to form seals between the supports 94 and the head 85.
The electrodes are supported at their lower portions 93 by two pairs of polyvinyl chloride spacers 102 which surround nylon bolts 101. Attached to the lower end of one of the electrodes is a baffle member made of an acrylic plastic 104 which is provided in order to prevent the pulsating saline solution which enters the chamber from port 66 from spurting between the electrodes 91 and 92 and cyclically varying the electrical properties of the condensing solution. Such spurting causes a pulsating current flow through the cell and renders the cell operation difficult to monitor and regulate. By providing the baffle 104, a more uniform and homogenous solution is maintained within the cell cavity 86. This also causes a more uniform electrolyzing current to flow between the electrodes by reducing the pulsating change with time of the properties of the solution between the electrodes.
To direct the solution along an axial path between the electrodes, a pair of non-conductive plates 105 extend between each of the opposite edges of the electrodes from their tops to approximately one-half inch from their bottom ends. The plates 105 are preferably transparent to facilitate inspection.
Referring again to Figure 1, the electrical control circuit 110 includes a power supply which connects to the AC line 28 through a paiT of fuses 112 and the on/off switch 23 located on the panel 27. The switch 23 is a double-pole single-throw switch which connects either 110 or 220 volt AC power to the unit line voltage lines 113 and 114. The lines 113 and 114 are connected across the primary winding 115 of a step-down transformer 116 which has a 24 volt secondary winding 1~74;Z5Z

117. A power "ON" indicator light 24 is connected across the winding 117. One of the terminals 121 of the transformer secondary winding 117 is connected to the wiper contact 122 of the wand tTigger switch 38 through the cable 37. The switch 38 is also provided with a normally-opened OFF contact 124 and two contacts 125 and 126, which are connected through relay windings 131 and 132 respectively to the other secondary terminal 118 of the transformer 116.
The relay 131 is actuated when the trigger switch 38 is in the flush position 125. This relay 131 operates relay contact set 131-1 which connects the solenoid winding 72 across the AC lines 113 and 114. Similarly, a contact set 132-1 is connected in parallel across the contacts 131-1 to similarly energize the solenoid 72 when the switch 38 is in the sanitizing position. A second set of contacts 132-2 of the relay 132 operates, when the switch 38 is in the sanitize position, to connect the winding of the motor 59 across the lines 113 and 114. Connected across the motor winding leads 142 is the primary winding 144 of a transformer 145. The transformer 145 is a step-down transformer having an approximately 20 volt output secondary winding 146. The center tap 147 of the secondary 146 is connected through the current meter 25 to the anode 91 of the cell 70, the cathode 92 of the cell 70 being grounded. The opposite ends of the winding 146 are connected to the anodes of a respective one of a pair of diodes 151, each of which has its cathode connected to ground at point 152.
The center tap 147 furnishes a rectified full-wave negative output to the anode 91 of the cell 70.
To initially condition the central unit 20, the brine tank 52 is filled with approximately 20 pounds of granulated and non-iodized table salt. Then by connecting inlet port 29 to tap water at a pressure of about 40 to 65 psi, the tank 52 is filled until float valve 81 shuts off the flow. The flow of the tap water causes switch 80 to energize pump 77 which pumps prescribed quantities of acid into tank 52. When this is completed, the valves 73 and 64 are opened to ready -107~;~S2 the unit for spray operation.
In operation, an operator orients the wand 30 so that the nozzle 42 is directed toward the objects ll or 12, the surfaces of which are to be disinfected. The operator can initiate the sanitizing procedure by actuating the switch 38 to the sanitize position, thereby actuating the relay 132 and closing the sets of contacts 132-l and 132-2 to energize the solenoid 72, opening the valves 71, causing clear water to flow into the inlet 66 of the cell 70. Also, the closing of the relay contacts 132-2 energizes the pump motor 59, causing the pump 58 to pump saline solution which mixes with the clear wat0r at the "T" 63 to enter the inlet 66 of the cell 70. Simultaneously, the rectifier 140 is energized to supply electrolyzing current to the cell 70 to electrolyze the solution flowing through the cell 70, causing a chlorinated disinfecting solution to bè emitted from the cell outlet 69 through the "T" 68 and the central unit outlet 31, through the hose 32 and the inlet 35 of the wand 30 and then through the tube 43 of the wand 30 and out of the nozzle 42 in the form of a continuous liquid stream upon the objects 11 and 12.
The salinity of the solution, and thus the chlorine strength of the generated solution, is controlled by coordinating the settings of the cam on the pump motor shaft 61 to control the displacement of the pump 58 with the setting of the valve 73 in the clear water input line. For example, if the ratio of the incoming fresh water to the brine solution is maintained at about 72:1, a six inch electrolytic cell will generate 100 parts per million of free chlorine (substantially entirely in the form of hypochlorous acid) at one-half gallon per minu~e flow rate. The six inch cell refers to a cell wherein the electrodes are each 6" X 2 1/4" and operated at 14-17 volts across the electrodes and at a current of 25-30 amps. The solution may be further diluted to reduce the parts per million of chlorine where the particular sanitizing application admits of a lower proportion of chlorine. Further dilution as, for example, up to 100:1 does not - lot74;~s;~

adversely affect the pH of the solution, assuming the pH of the incoming fresh water is 7. Where the pH of the incoming water is more alkaline, the pump 77 should be varied to increase the proportion of acid into the solution from two ounces per gallon of saline solution.
The invention admits of the production of a cidal solution having a substantially greater chlorine concentration by using larger ; cells and connecting them in series. For example, the concentration can he increased to two thousand parts per million or even greater should a particular situation require it.
The foregoing description sets forth novel methods and systems wherein far greater bactericidal effectiveness is achieved in a system in which disinfecting by means of spraying or fogging solutions upon solid objects to be disinfected is desired.
As indicated above, the invention has application to the disinfecting of meat carcasses. The solution of the invention, that is, the low pH electrolytically generated chlorinated solution, may be utilized in any one of several different ways. For example, one operstor employing a single nozzle might spray a carcass for about thirty seconds at a rate of one-half gallon of solution per minute, the solution having a chlorine concentration from twenty-five to two hundred parts per million. Alternatively, the carcass could be subjected to a multiple nozzle spray as, for example, twelve nozzles spraying for about ten seconds.
Still another alternative method would involve the prewashing of the carcass with potable tap water followed immediately by creating a dense fog of the solution of the invention surrounding the carcass.
In the fogging method, the volume rate of spray is markedly reduced.

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. The method of creating a bactericidal solution comprising the steps of: mixing sodium chloride, an acid and sufficient water to provide a solution having pH of approximately 6, and electrolyzing the solution to generate nascent chlorine which is mainly in the form of hypochlorous acid.

2. The method as in claim 1 in which approximately two ounces of acid are added for every United States gallon of concentrated sodium chloride solution.

3. The method as in claim 1 in which said acid and water are initia-lly mixed with an excess of sodium chloride, said resultant solution and a substantial quantity of fresh water being pumped to an electrolytic cell.

4. The method as in claim 1 wherein the acid is 85% glacial acetic acid.

5. The method as in claim 1 wherein two ounces of glacial acetic acid is added for each United States gallon of concentrated sodium chloride solution.