NO308697B1 - Method and apparatus for producing pure elemental iodine - Google Patents

Description

The present invention relates to a method and device for the production of pure elemental iodine.

Iodine (e.g. in the form of Lugol's solution or as iodine tincture) has long been considered an effective biocide. The US Pharmacopoeia and other similar publications in a number of countries have documented this property of iodine since 1830. Iodophores have been noted for their similar properties since 1960.

These iodine compounds have become known for their bioactivity in humans, animals and in bacterial species in plants and their seeds.

It is a fact that iodine deficiency has been shown to prevent the achievement of maximum health, growth and successful reproduction.

It has recently been shown that the active component in all biological iodine compounds is thermodynamically free iodine, which is uncomplexed or pure elemental iodine (I2), as described in the article by Schmidt and Winicov "Detergent/Iodine Systems" in Soap and Chemical Specialties, August 1967. It has also recently been shown that when thermodynamically free iodine is administered to a mammal it has a very reduced effect on the thyroid gland compared to iodide, or iodine/iodide mixtures or mixtures of polyhalides (see Thrall and Bull in their article "Differences in the Distribution of Iodine and Iodide in the Sprague-Dawley Rat" in Fundamental and Applied Toxicology, 15, 75-81 (1990)).

The term thermodynamically free iodine describes iodine that is not complexed. Thermodynamically free iodine in aqueous solution can dissociate into a number of hydrolyzed forms depending on concentration and/or pH, e.g. HIO (also known as HOI), some of which have a biocidal nature. If a solution of aqueous iodine (I2+ hydrolyzed biocidal forms, if appropriate) could be safely formed at any concentration of thermodynamically free iodine less than supersaturation, and remain stable at this level, it would allow the fabrication of a variety of devices that could be used in water treatment, instrument sterilization, application as a source of nutritional iodine plus other medical applications including the treatment of IDDs (Iodine Deficiency Disorders), chemical applications and catalytic applications. If a device in a safe way, e.g. could produce a desired concentration of thermodynamically free iodine in a pH-buffered fluid such that the thermodynamically free iodine remained unhydrolyzed and at a known concentration despite moderate changes in ambient temperature, would allow the treatment of a variety of non-thyroidal IDDs and other medical conditions which are known to respond to treatment with iodine, as in US patent no. 4,816,255 after Ghent, with a greatly reduced toxicity (toxicity in the sense of thyroid complication found with other forms of iodine, iodides, iodine/iodide mixtures or polyhalides).

In an attempt to produce biocidal iodine compounds, a number of methods of both a chemical and mechanical nature have been devised. To date, however, these methods have had limited application and commercial success for reasons due to the chemical and physical properties of iodine such as low solubility in H20, reactivity, easy contamination, or the production of polyhalides and iodides and other potentially harmful excipients that inhibit the presence of thermodynamically free iodine or its application in certain areas.

Thermodynamically free iodine in all biocidal iodine solutions, whether alcohol/water, surfactant/water or other complexing agents/water is limited to the water phase. Furthermore, thermodynamically free iodine is usually found in solution in concentrations less than those of the total titratable iodine in solution. In e.g. Lugol's solution where potassium iodide (Kl) is used to form a reservoir of iodine as I3 through the ratio I2+ ni"<±>5I" + In, the solubility of elemental iodine is increased to e.g. 1% (w/v), the amount of thermodynamically free iodine being detectable, however, is only about 0.018% (w/v) or 180 ppm. The germicidal capacity of these iodine preparations is dependent on the continuous release of thermodynamically free iodine from the reservoir of titratable iodine, as thermodynamically free iodine in solution disappears through dilution, contamination or biocidal activity. An attempt has therefore been made to develop a practical method to form this reservoir from which purely thermodynamically free iodine can be released alone, without other additives, into water in a controlled manner.

Attempts have been made to develop a means of mechanically containing a quantity of metallic elemental iodine in contact with water, as shown in US Patent No. 3,408,295, issued October 29, 1968 in the name of John A. Vaichulis and US Patent No. 4,384. 960 issued May 24, 1983 in the name of Richard D. Polley. However, these methods have not been completely effective when it comes to preventing microparticles (and sometimes macroparticles) of iodine crystals from being carried away with the water flow. Furthermore, these methods cannot prevent the contamination of the iodine reservoir with undesired substances that can reduce the efficiency of the reservoir, or remedy the release of undesired contaminating substances more easily into the product stream containing the desired thermodynamically free iodine and they furthermore cannot provide stable levels of thermodynamically free iodine iodine below the saturation level of iodine in a fluid in contact with iodine.

Attempts have also been made to develop a chemical means to provide a reliable supply of thermodynamically free iodine. The main flaw with such systems (eg Lugol's solution, iodine tincture, iodophors) is that the loss of solvent (ie water lost through evaporation) increases the total percentage of iodine in a volume and, with the relative insolubility for iodine, the toxic effect of the remaining solution will increase (through recrystallization of elemental iodine) and consequently the availability of thermodynamically free iodine will be reduced.

Another problem with chemical agents is that the level of thermodynamic free iodine in water is usually limited to about 60% of the maximum solubility of thermodynamic free iodine in water (which is about 0.03%). This is approximately 180 ppm (0.018%) and is usually found to be much less than this. An iodophore of 3.75% titratable iodine can e.g. achieve a maximum strength of less than 40 ppm of thermodynamically free iodine after dilution, having 75 ppm of titratable iodine. This mismatch between the level of thermodynamically free iodine and the amount of titratable iodine makes field testing for iodine concentrations very cumbersome.

Where chemical additives are used to increase the reservoir of titratable iodine, the additives can act as unwanted toxins. In the medical field, iodine can be used in a number of ways (ie rinsing wounds or incisions in connection with operative procedures) and a mixture used for this purpose was P.V.P.I. (poly(N-vinyl-2-pyrro-lidone)-iodo). Finally it was realized that P.V.P. (poly(N-vinyl-2-pyrrolidone)) macromolecule had a tendency to accumulate in the lymph glands of a patient, which led to problems in connection with the gland's function. This is an example of excipients causing unwanted side effects.

Finally, thermodynamically free iodine should be as pure as is both practically and economically achievable for the final intended applications. Any existing chemical means of releasing thermodynamically free iodine is likely to release unwanted contaminants into the final product.

An object of the present invention is therefore to provide a safe method for obtaining pure thermodynamically free iodine.

It is a further object of the invention to provide a device for obtaining pure thermodynamically free iodine.

A further object of the invention is to show a method and a device for obtaining thermodynamically free iodine in any predetermined concentration.

The present invention relates to a method and device for the production of pure elemental iodine where a source containing thermodynamically free iodine is introduced on one side of a non-porous barrier which is impermeable to solvents and contaminants for thermodynamically free iodine (hereinafter referred to as an iodine- solvent solid barrier), through which said thermodynamically free iodine passes by dispersion driven by the vapor pressure difference between the two sides of the barrier until equilibrium is reached for the vapor pressure of thermodynamically free iodine across the barrier.

In a preferred embodiment of the invention, the degree of dispersion of thermodynamically free iodine to the other side of the iodine-dissolving solid barrier can be controlled by means of means which reduce the vapor pressure of thermodynamically free iodine, such as variation of the temperature of the iodine source material or of the other side of the barrier, as well as using an iodine complexing compound together with or in combination with the source material.

The present invention thus relates to a method for the production of pure elemental iodine, which is characterized by the steps of providing a source containing thermodynamically free iodine on one side of an iodine-dissolving solid barrier which is impermeable to solvents and contaminants for thermodynamically free iodine, and with collection, on the other side of the barrier, of thermodynamically free iodine dispersing through the barrier until equilibrium is achieved between the vapor pressures of thermodynamically free iodine across the barrier.

The invention also relates to a device for the production of pure elemental iodine, which is characterized in that it comprises an iodine-dissolving solid barrier that is impermeable to solvents and contaminants for thermodynamically free iodine, the barrier delimiting a closed space for placing a source containing thermodynamically free iodine on one side of the barrier, and a container, which may be closed or open, to collect thermodynamically free iodine passing through the iodine-dissolving solid barrier upon dispersion.

Finally, the invention relates to a device for the production of pure elemental iodine, which is characterized by the fact that it includes:

a container,

a cup-shaped object in the container which opens out from the container and defines a sealed cavity therebetween carrying a source containing thermodynamically free iodine,

an iodine-dissolving solid barrier which coats the cup-shaped object inside the cavity, said cup-shaped object being perforated into the barrier,

the container and the cup-shaped object being formed of iodine-impermeable material.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings show examples of embodiments in which: Fig. 1 is a schematic drawing showing a device for

production of pure elemental iodine,

Fig. 2 is an alternative embodiment of fig. 1,

Fig. 3 is an alternative embodiment of fig. 1, and

Fig. 4 is a cross-section of an alternative embodiment of

fig. 1.

Elemental iodine, i.e. the diatomic molecule I2, is only marginally soluble in water (approx. 300 ppm). In a variety of other fluids, iodine can form two distinct types of solution that can be distinguished from each other by their color (ie, in organic solvents such as carbon tetrachloride, iodine gives a violet color on solution, while in water it forms a clear amber color in the absence of polyhalides , complexing agents or other dyes. In the presence of polyhalides, a black color is formed). In these liquids, iodine will give a vapor pressure and also has a maximum solubility limit. In the presence of polyhalides and/or iodine-complexing compounds, the vapor pressure of iodine is reduced.

Iodine also has the special property that it is soluble in certain solids. These solids will behave like a liquid solvent towards iodine (in the traditional sense with properties like a liquid). When iodine is introduced into these solids, iodine will penetrate the solid and give one of the two colors observed when iodine dissolves in liquids. In addition, iodine will produce a vapor pressure above the solid and also has a solubility limit within the solid, both of which can be affected by complexing the I2 within the solid, or from the I2 reservoir or between the solid and the reservoir.

A number of these special solids are impermeable to water and other solvents for iodine. If a solution containing a quantity of iodine is therefore placed on one side of the fixed barrier and a solvent for iodine is placed on the other side of the fixed barrier, I2 will freely move back and forth across the barrier until equilibrium is achieved. This equilibrium is reached when the vapor pressure of iodine above the reservoirs on both sides of the barrier and above the barrier itself is equal. In addition, by selecting the appropriate source of release of thermodynamically free iodine (ie, iodine in combination with or in association with different types and concentrations of iodine-complexing compounds) to control the vapor pressure above an iodine-releasing solution, the final concentration of the other side of the barrier is precisely controlled for a given temperature and solvent on the other side of the barrier, and can even be made stable regardless of moderate temperature changes in the donor source, in the barrier, or in the solvent on the other side of the barrier.

By adjusting the temperature of the donating source, barrier or solvent on the other side of the barrier, the vapor pressure of thermodynamically free iodine can also be precisely controlled to give a desired concentration that is eventually reached on the other side of the barrier.

Fig. 1 in the drawings shows a container 10 through which iodine molecules cannot penetrate, such as glass, a solid barrier 12 constructed from an iodine-dissolving solid, an iodine source 14 in a chamber 16 containing a fluid and another chamber 18 on the other side of the barrier 12 containing a material such as thermodynamically free iodine, which disperses through the barrier 12, will pass into until vapor pressure equilibrium is achieved. The chamber 18 can be a fluid such as water, a vacuum chamber, an iodine-dissolving solid which is used to retain thermodynamically free iodine, an iodine-complexing compound or additive or other material to which one wishes to expose a controlled amount of iodine.

One of the solid substances that exhibits this iodine-dissolving property is polyethylene with both high and low density. It may be preferred, but not essential, that the volume of the dissolving solid be low to reduce the amount of iodine required to achieve an equilibrium concentration, within the barrier, with respect to the final concentrations of the contents of the two chambers 16 and 18. Due of this, a small volume of iodine-dissolving solid is preferred, which gives rapid

adaptation and equilibration of the vapor pressure in all elements.

Fig. 2 in the drawings shows an alternative layout of the components in fig. 1 where the iodine-dissolving solid 20 encapsulates the iodine source (water plus an amount of material which provides thermodynamically free iodine). The capsule will be capable of releasing an amount of thermodynamically free iodine to achieve a desired level of thermodynamically free iodine in the material contained in the chamber 22. The encapsulation prevents solvents or contaminants from coming into direct physical contact with the contents of the capsule. The encapsulation process should be carried out using materials that add a minimum of iodine. The capsule can be formed as a cushion with or without a rim. When placed in the chamber 22, the capsule 20 will facilitate the transport of I2 molecules to the material in the chamber 22 and it will do this until the iodine reservoir is emptied or until equilibrium is achieved between the reservoir 14 and the chamber 22. If an amount of thermodynamically free iodine in the reservoir 22 is lost due to biological action, complex formation or for other reasons and therefore disturbs the achieved thermodynamic equilibrium for the vapor pressure, more iodine will migrate through the capsule wall 20 until the same equilibrium for the vapor pressure is again achieved.

Fig. 3 in the drawings shows an alternative assembly where the iodine-dissolving solid barrier 12 is flexible and carries within it an iodine-non-dissolving fragile container 22 which contains the iodine source 14. Application of this embodiment results in the flexible barrier 12 being pressed together to break the non-dissolving barrier 22 so that the iodine source solution has access to the dissolving barrier. The entire assembly is transferred to the material where the thermodynamically free iodine, which then diffuses through the barrier 12, is to be used.

For this embodiment, an example of an iodine source 14 would be potassium iodide (Kl), and a possible fluid surrounding the fragile container 22 and which is limited by the solid solvent barrier 12 could be a water and chloramine mixture. When the fragile container 12 is broken, the chemical reaction between potassium iodide and chloramine will yield potassium chloride and thermodynamically free iodine (plus some free amines).

The device shown in fig. 4 in the drawings consists of unit 30 which comprises a cup-shaped object 31 which fits into a container 32 in such a way that an annular cavity 34 is formed between the two. Both the cup-shaped object 31 and the container 32 are made up of materials which are impermeable to iodine (such as glass). A removable screw cap (not shown) fits the cup-shaped object 31 by connection to a thread 36. The object 31 has an annular rim 37 which seals through the rim 38 of the container 32. The annular cavity between the cup-shaped object 31 and the container 32 is filled with an iodine source 35 from which thermodynamically free iodine will be extracted.

The outer surface of the object 31 below the edge 37 is coated with an iodine-dissolving solid layer 39. A ring of holes 42 around the object 31 and a series of holes 44 in the bottom of the object 31 bring the contents of the object 31 into contact with a surface of the iodine-dissolving solid barrier 39. The bottom of the cup-shaped object 31 is spaced from the surface of the container 32 by means of an annular rim 46 having notches 48 located around the circumference.

To disinfect a quantity of water, this quantity is poured into the cup-shaped object 31 approximately to the level of the holes 42. The lid is then screwed onto the object 31 and the whole unit is shaken. The lid is removed and the water in the beaker is now colored brown with thermodynamically free iodine in solution. The colored water can now be tested to determine the amount needed to disinfect a specific amount of water. This can be done by dipping a piece of starch paper into the iodine-containing water in the cup-shaped object 31 and comparing the blue color on the paper strip with a standard color chart. Should a suitable excipient/iodine mixture capable of complexing I2 and reducing its vapor pressure be used for the material that emits thermodynamically free iodine, it will not be necessary to test the concentration as a known concentration will exist in the product material.

This method and device has a number of advantages in that:

1) the iodine-filled device has an unlimited shelf life,

2) the iodine cannot be contaminated,

3) as long as the source reservoir is not completely emptied, the contents of the cup-shaped object will always achieve the same final concentration of thermodynamically free iodine regardless of the volume of water introduced into the object, 4) loss of water from the cup-shaped object through processes such as evaporation will not increase the toxicity of the final solution, as the excess of thermodynamically free iodine will only diffuse back to the iodine source, 5) there is no need to use harmful additives on one (product) side of the dissolving barrier, 6) loss of thermodynamically free iodine on the other side of the dissolving barrier will automatically be replaced by thermodynamically free iodine diffusing from the source side of the dissolving barrier, and 7) when water is applied to the other (product) side of the barrier, the resulting solution is unexpectedly non-toxic, non- irritating, non-burning to skin and mucous membranes, it is bactericidal and has an effect on the thyroid that is less than 30% a v the harmful effect of other iodine compounds, iodide mixtures, iodide/iodine mixtures or polyhalides.

In each of the embodiments described, the iodine-dissolving barrier may be formed of, but is not limited to, materials such as straight chain polyethylene, isotactic polyethylene, polyoxymethylene, and polybutylene terephthalate. The barrier will be chosen so that it cannot contribute to damaging the end use of the products.

Any of these iodine-resolving solid barriers may be impregnated with an iodine-complexing compound to control the level of thermodynamically free iodine on the product side of the barrier. Examples of impregnation materials can be Kl, Nal and Lii.

In each embodiment, the source of thermodynamically free iodine can be a variety of compounds including, but not limited to, technical grade iodine containing thermodynamically free iodine.

In each embodiment, iodine complexing compounds known to lower the maximum level of thermodynamically free iodine by complexing I2 iodine and therefore lowering the iodine vapor pressure above the iodine/complexing compound mixture can be used to precisely control the equilibrium concentrations of thermodynamically free iodine on the other side of the barrier. This can be achieved by combining iodine and complexing compounds and using the mixture as a source of thermodynamically free iodine. Another method is to separate the iodine source from the iodine-dissolving solid barrier by means of another and similar barrier, and where the iodine-complexing compound is placed between the two barriers. The effectiveness of the complexing compound can be varied with type and concentration. Examples of iodine-complex-forming compounds are (poly(N-vinyl-2-pyrrolidone), polyoxypropylene and nonylphenol. A more comprehensive statement is shown in US patent no. 3,028,299 by Winicov and Schmidt.

In each embodiment, the other side of the solid solvent barrier to which the thermodynamically free iodine from the source material is to disperse may contain a fluid (liquid or gas) or a solid. The fluid or solid can either be iodine-soluble or iodine-non-solvent. On the other hand, there can also be a vacuum where thermodynamically free iodine will form an iodine vapor and whose concentration in the vacuum is controlled by the vapor pressure exerted by the iodine source. Furthermore, the other side of the iodine-solubilizing solid barrier may contain an iodine-complexing compound that will complex thermodynamically free iodine crossing the barrier.

In each embodiment, the temperature of the iodine source, iodine-dissolving solid barrier or material on the other side of the barrier can be adjusted to control the vapor pressure of thermodynamically free iodine in this iodine source, iodine-dissolving solid barrier or material on the other side of the barrier and on this way control the degree of thermodynamically free iodine that passes through the barrier.

Claims (37)

1. Process for the production of pure elemental iodine, characterized by the steps of providing a source (14, 35) containing thermodynamically free iodine on one side of an iodine-dissolving solid barrier (12, 20, 39) which is impermeable to solvents and contaminants for thermodynamically free iodine, and with collection, on the other side of the barrier (12, 20, 39), of thermodynamically free iodine dispersing through the barrier (12, 20, 39) until equilibrium is achieved between the vapor pressures of thermodynamically free iodine over the barrier (12, 20, 39) . 2. Method as stated in claim 1, characterized in that the iodine source (14) is encapsulated within the iodine-dissolving fixed barrier (20). 3. Method as stated in claim 1, characterized in that thermodynamically free iodine is collected in a liquid. 4. Method as stated in claim 3, characterized in that said liquid is water. 5. Method as stated in claim 1, characterized in that thermodynamically free iodine is collected in a gas. 6. Method as stated in claim 1, characterized in that the aforementioned other side of the iodine-dissolving fixed barrier (12, 20, 39) is constituted by a vacuum. 7. Method as stated in claim 1, characterized in that thermodynamically free iodine is collected in an iodine-dissolving solid. 8. Method as stated in claim 1, characterized in that thermodynamically free iodine is collected on the surface of a solid in which iodine is not soluble. 9. Method as stated in claim 1, characterized in that thermodynamically free iodine is collected in an iodine-complex-forming compound. 10. Method as set forth in claim 1, characterized in that the iodine source (14, 35) consists of a mixture of an iodine/iodine complex-forming compound which is calibrated to reduce the vapor pressure of thermodynamically free iodine by a predetermined amount. 11. Method as stated in claim 1, characterized in that the iodine source (14) is separated from the iodine-dissolving solid barrier (12, 20, 39) by a further iodine-dissolving solid barrier and where an iodine-complexing compound is provided between the two barriers. 12. Method as set forth in claim 9, 10 or 11, characterized in that the iodine complex-forming compound is selected from potassium iodide, sodium iodide, lithium iodide, poly(N-vinyl-2-pyrrolidone), polyoxypropylene and nonylphenol. 13. Method as stated in claim 1, characterized in that the iodine-dissolving solid barrier (12, 20, 39) is a plastic material. 14. Method as stated in claim 13, characterized in that the plastic material is selected from straight-chain polyethylene, isotactic polyethylene, polyoxymethylene and polybutylene terephthalate. 15. Method as stated in claim 1, characterized in that the iodine-dissolving solid material is impregnated with an iodine complex-forming compound. 16. Method as stated in claim 15, characterized in that the impregnating compound is selected from sodium iodide, potassium iodide and lithium iodide. 17. Method as stated in claim 1, characterized in that the temperature can be controlled in the said source (14, 35), in the said barrier (12, 20, 39) or on the said other side of the barrier (12, 20, 39) . 18. Device for the production of pure elemental iodine, characterized in that it comprises an iodine-dissolving solid barrier (12, 20) which is impermeable to solvents and contaminants for thermodynamically free iodine, the barrier (12, 20) delimiting a closed space for placement of a source (14) containing thermodynamically free iodine on one side of the barrier (14), and a container (10), which may be closed or open, to collect thermodynamically free iodine passing through the iodine-dissolving solid barrier ( 12, 20) by dispersion. 19. Device as stated in claim 18, characterized in that the iodine source (14) is encapsulated within the iodine-dissolving fixed barrier (20). 20. Device as stated in claim 18, characterized in that the container (10) for collecting thermodynamically free iodine is designed to contain a liquid. 21. Device as stated in claim 20, characterized in that said liquid is water. 22. Device as stated in claim 18, characterized in that the container (10) for collecting thermodynamically free iodine is designed to contain a gas. 23. Device as stated in claim 18, characterized in that the product side of the iodine-dissolving solid barrier (12, 20) is constituted by a vacuum. 24. Device as stated in claim 18, characterized in that the container (10) for collecting thermodynamically free iodine is designed to contain an iodine-dissolving solid. 25. Device as stated in claim 18, characterized in that thermodynamically free iodine is collected on the surface of a solid in which iodine is not soluble. 26. Device as stated in claim 18, characterized in that thermodynamically free iodine is collected in an iodine-complex-forming compound. 27. Device as stated in claim 18, characterized in that the iodine source (14) consists of a mixture of iodine and an iodine-complexing compound, calibrated to reduce the vapor pressure of thermodynamically free iodine by a predetermined amount. 28. Device as stated in claim 18, characterized in that the iodine source (14) is separated from the iodine-dissolving solid barrier (12, 20) by a further iodine-dissolving solid barrier and where an iodine-complex-forming compound is provided between the two barriers . 29. Device for the production of pure elemental iodine, characterized in that it comprises: a container (32), a cup-shaped object (31) in the container (32) which opens out from the container (32) and defines a sealed cavity (34) therebetween carrying a source (35) containing thermodynamically free iodine, an iodine-dissolving solid barrier (39) which coats the cup-shaped object (31) inside the cavity (34), the said cup-shaped object (31) being perforated into the barrier (39), the container (32) and the cup-shaped object (31) being formed of iodine-impermeable material. 30. Device as stated in claim 29, characterized in that the iodine source (35) consists of a mixture of iodine and an iodine-complexing compound, calibrated to reduce the vapor pressure of thermodynamically free iodine by a predetermined amount. 31. Device as stated in claim 29, characterized in that the iodine source (35) is separated from the iodine-dissolving fixed barrier (39) by a further iodine-dissolving fixed barrier and in which an iodine-complexing compound is provided between the two barriers. 32. Device as stated in claim 26, 27, 28, 30 or 31, characterized in that the iodine complexing compound is selected from potassium iodide, sodium iodide, lithium iodide, poly(N-vinyl-2-pyrrolidone), polyoxypropylene and nonylphenol. 33. Device as stated in claim 18 or 29, characterized in that the iodine-dissolving solid material is a plastic material. 34. Device as stated in claim 33, characterized in that the iodine-dissolving solid material is selected from straight-chain polyethylene, isotactic polyethylene, polyoxymethylene and polybutylene terephthalate. 35. Device as stated in claim 18 or 29, characterized in that the iodine-dissolving solid material is impregnated with an iodine-complex-forming compound. 36. Device as stated in claim 35, characterized in that the impregnating compound is selected from sodium iodide, potassium iodide and lithium iodide. 37. Device as stated in claim 18 or 29, characterized in that the temperature in said source (14, 35), said barrier (12, 20, 39) or on the said other side of the barrier (12, 20, 39) can be controlled.