WO2009068925A2

WO2009068925A2 - Method for spraying, sprayer and herbicide composition

Info

Publication number: WO2009068925A2
Application number: PCT/HU2008/000140
Authority: WO
Inventors: Gyula BOHÁR
Original assignee: Biovéd 2005 Kft; MTA Növényvédelmi Kutatóintézete
Priority date: 2007-11-30
Filing date: 2008-11-28
Publication date: 2009-06-04
Also published as: HU0700768D0; HUP0700768A2; WO2009068925A3

Abstract

The invention relates to a method for spraying spray solution, which method is characterised by that the spray solution is sprayed onto the plants from a lateral direction. The invention also relates to equipment for the realisation of the method, which has a container for accommodating the spray solution, a liquid forwarding unit, at least one nozzle and one or more pipes connecting the nozzle to the container through the liquid forwarding unit, and which equipment is characterised by that it is constructed in a way suitable for changing the exit direction of the spray solution preferably within the angle range of about ± 45° with respect to the horizontal plane, and/or in order to control the exit direction of the spray solution the equipment is connected to the vehicle used for carrying the equipment in a way enabling the alteration of its position with respect to the vehicle. Furthermore, the invention relates to a herbicide composition for killing composite weeds, especially ragweed, which consists of an 8% - 19% aqueous solution of one or more salts and is characterised by that it contains mainly or exclusively potassium chloride as its salt component.

Description

Method for spraying, sprayer and herbicide composition

The invention relates to a method for spraying, a sprayer for the realisation of this method, and a herbicide composition, especially a composition for killing composite weeds.

The necessity of protecting against weeds appeared at the same time as agricultural production. The appearance of weeds reduces cultivated plant yields by reducing their growing space, reducing the amount of available nutrients and other sources (e.g.: light, water), making harvesting difficult, etc. Furthermore, weeds may cause diseases both in cultivated plants and in animals and people living in their environment or getting in contact with them, for example, by eating them. Due to the latter causes, today fighting against weeds is not simply an activity closely related to agriculture, but in many cases it is an activity performed independently of agriculture, for example, in respect of allergenic plants growing on inhabited areas.

Protection against weeds may include several methods. One of the most obvious solutions is mechanical killing following visual inspection, that is, removing the weed using a cutting tool (scythe) after the given weed species is recognised. This method is expensive, complex and difficult, and it is used only at places where other solutions (see below) cannot be used, for example, on inhabited areas. This method is not suitable for killing ragweed, especially because ragweed shoots again after scything, and deficient scything or scything performed at the wrong time may result in increasing flowering and pollen production. Mechanical killing is also possible by using soil cultivation methods, such as hoeing or harrowing.

Another possible solution involves using the natural enemies of weeds, that is, biological protection. It may involve the use of micro-organisms (bacteria, viruses, fungi), insects or even mammals that kill the given weed. The disadvantage of biological protection is that, on the one hand, it is difficult to find the biological enemy of the given weed species, and, on the other hand, after killing the weed the natural enemy itself does not necessarily die, and in its search for another host organism or nutrient it may also attack plants other than the target-plants.

The use of genetically modified cultivated plants is a type of biological protection. Such plants, due to one or more artificially added genes, may produce materials that destroy weeds harmful to them. Presently the use of genetically modified plants encounters intensive social and scientific opposition, first of all because of worries concerning safety (for example, when a genetically modified plant is removed from an agricultural area to a natural environment, it may cause damage by emitting foreign protein it produces there).

On agricultural areas the use of chemical weed control materials (so-called herbicides) is the most widely spread technique. Generally they provide a cheap and quick solution. A significant proportion of herbicides are organic compounds. Such herbicides include specific and less specific general agents. For example, clopyralid is a preparation that kills ragweed and composite weeds related to it, there are preparations killing dicotyledons, such as, for example, atrazine, dicamba, mesotrione, and there are non-selective herbicides, among which glyphosate is worth mentioning. The above herbicides, except for glyphosate, all exert their effects on small sized weeds only, and they may not be used on or near inhabited areas. The use of organic compounds as herbicides may have several disadvantages. On the one part their production in chemical industrial plants may represent a significant load on the environment, and their decomposition in nature (that is the creation of metabolites) may result in the appearance of further organic compounds in the soil, in the cultivated plants, in the surrounding natural fauna, and also in the groundwater and natural waters, and consequently even in drinking water for human use.

The disadvantages of the above possibilities of weed killing and weed control do not appear in the case of using inorganic herbicides. First of all they include salts, which are more or less specific with respect to certain plant types depending on their resistance to osmotic effects. When the solutions of inorganic salts get in contact with the green surfaces of plants, they result in an osmotic shock in the plants causing them to wither due to significant dehydration. The basic materials of such salt solutions are easy to obtain, and the consequences of them getting into the environment can be precisely assessed. However, when inorganic salts are used in large amounts, they may result in a significant loading of the environment, for example, all salts in general increase the ionic strength of the soil, or, for example, salt solutions containing sodium ions may result in the salinisation of the soil. (Sodium chloride, also known as common salt, is becoming less widely used for gritting roads in cold weather because it has such effects damaging the environment.)

In Southeast Asia sodium chloride (common salt, NaCl) has been used for a long time on rice fields for killing composite weeds. It was recorded already in 1955 that sodium chloride may be an efficient weed killer, but non- selectively it may result in the destruction of all vegetation (Frear, Chemistry of Pesticides, 3^rd edition, page 401, 1955).

In patent document No. US 5,330,964, sodium bicarbonate is mentioned as the basic material of a method used for controlling low vegetation, where bicarbonate forms a layer on plants.

In Hungarian patent application no. P0501004 a preparation for killing ragweed is described, which contains 0.15-0.25 kg of inorganic salt, especially common salt, in 1 litre of water, together with 8-14 g of dissolved lime, and optionally together with a surface-active material. The preparation is applied onto plant leaves by spraying.

Patent document No. US 6,372,690Bl describes a method for selective weed killing using a nontoxic 8-12 mixed % (weight per volume, that is w/v) sodium chloride aqueous solution, according to which the solution is to be applied to the leaves of plants, optionally together with a surface-active agent. In the specification the invention is explained through examples of fighting against ragweed. Apart from NaCl, in the examples potassium nitrate (KNO₃) is also mentioned, which, however, did not prove to be efficient. It was found that the 12 w/v% NaCl solution is optimal, NaCl solutions more concentrated than 20 w/v% do not show any additional effect. In the case of solutions prepared by adding surface-active agents (which ensure better spreading of the solution on the plant leaves and consequently its more efficient use), the 8w/v% NaCl solution proved to be as efficient as the 12 w/v% NaCl solution without any surface-active agents, containing only sodium chloride. It was also found that solutions below a concentration level of 8 w/v% are not efficient. Among possible salts numerous chlorides and numerous potassium salts are listed, for example, potassium chloride, but in other parts of the patent specification exclusively uses relating to sodium chloride are described, and KNO₃ is mentioned as a compound not suitable for efficient weed killing in the given concentration. The 8-20 v/w% salt solution described here, and especially the NaCl solution of such concentration does not comply with the presently asserted principles of environmental protection, as such a high concentration of any salt increases the ionic strength of the soil on the given area to an unacceptable extent, and NaCl is especially unsuitable for use as a herbicide, as apart from increasing the ionic strength, it also increases the harmful salinisation of the soil. On the basis of the above it can be seen that according to the state-of-the-art technology no weed killing method or herbicide is known that can be accepted from all aspects for killing composite weeds, especially ragweed.

Generally the presently known spraying methods and equipment apply spray solution onto the target plants (which spray may be a herbicide, insecticide, nutrient, wash liquid, etc., that is any solution that needs to be applied onto the surface of the target plant), by atomising the spray solution from the space above the highest point of the plant, and due to gravity the spray mist falls onto the plants. The disadvantage of these methods is that only plant surfaces above which there are no other plant parts, that is surfaces accessible to the spray mist falling from above, can be covered with the spray solution efficiently using this method.

Because of the disadvantages described above, the task to be solved with the invention is to provide a spraying method and equipment, with the help of which the spray solution, such as a herbicide, insecticide, nutrient, etc., can be sprayed onto the plants more efficiently than before, that is the spray solution can be utilised significantly more efficiently, or more exactly a larger surface of the plant to be sprayed can be covered.

The other task to be solved with the invention is to provide a herbicide composition against composite weeds, especially ragweed, which burdens the environment to a significantly lower and more predictable extent as compared to the herbicides known before both during its production process and use, and the production of which is more economical as compared to the production of herbicides known before, but in respect of its efficiency does not remain below other herbicides known before.

The invention is based on the recognition that if the spray solution is not sprayed onto the target plants from above in accordance with the method according to the state of the art, but from the side, that is from a direction at right angles to the stem of the target plants, then a greater proportion of the spray solution of a given quantity can be applied onto the surface of the plants, consequently spray solution of a smaller amount and/or lower active agent concentration is enough to realise efficient spraying.

According to our other recognition on which our invention is based, if instead of sodium chloride used to date, a herbicide is prepared using potassium chloride, then, on the one hand, the use of sodium ions resulting in the salinisation of the soil can be avoided, and, on the other hand, a material enters the environment that is useful for the environment and is also commonly used as an artificial fertiliser.

On the basis of the above recognitions, in accordance with the invention the set task was solved with the help of a method in the course of which a spray solution is sprayed onto the target plants, and which method is characterised by that the spray solution is sprayed onto the plants from a lateral direction.

If the solution is not sprayed onto the target plants from above in accordance with the ordinary method, but from the side, then a greater proportion of the spray solution of a given quantity can be applied onto the surface of the plants, consequently spray solution of a smaller amount and/or lower active agent concentration is enough to realise efficient spraying. The advantage of spraying from the side is that liquid drops moving into numerous different directions are created within a given space. Due to gravity, the drops moving in a lateral direction also have a component of movement towards the ground beside the lateral movement component, and the resultant of these components of movement is a parabolic curve. Viewing this movement in time, at the beginning of its path the spray drop moves approximately horizontally, and at the end of its path its movement becomes approximately vertical. Between the two extreme points (that is the horizontal and vertical movement) the movement of the drops is characterised by both components of movement, in a continuously changing proportion. During the atomising process practically each drop moves along a different parabolic course, as due to all the different factors determining the path of motion (size and weight of the drops, the blow intensity exerted on a given drop, the effects of the drops nearby, the local flowing profiles in the environment of the drop, etc.) each drop has its own individual course. If there is a target plant in the way of the atomised cloud of drops, some drops will run into the plant in their phase characterised mostly with a lateral movement component, some will run into the plant when already in the phase characterised mostly by a vertical movement component, and obviously there will be many drops hitting against the surface of the weed at an angle suiting a certain proportion of the two types of movement components at the moment of the impact. It follows from the above that if atomisation takes place from a lateral direction, a much larger surface of the target plan can be covered with the spraying agent than in the case of atomisation from above, in the course of which only the top of the plant can be covered, as in the course of atomisation from this direction suiting the state-of-the-art technology the drops moving towards the plant only have the vertical movement component. Consequently, the advantage of the method and equipment according to the present invention is that with their help spraying agents can be applied onto the surface of the target plants more efficiently, that is a lower concentration/amount of such agents needs to be used. As a result of this spraying becomes more environmental friendly and more cost efficient.

For example, the method according to the invention can be used for spraying herbicides. By using this method the surface of weeds is covered more efficiently, therefore the desired aim can be achieved by using herbicide solutions of a lower amount and/or lower concentration in a given case as compared to what is known in the state-of-the-art technology, which means that the surface of weeds can be covered to such an extent that via the osmotic shock caused it results in the destruction of the weed due to shrivelling. According to the state-of-the-art technology a salt solution of a concentration of at least 8 w/v% is needed for efficient use. (It is pointed out here that in the case of aqueous solutions there is a negligible difference between w/v% and mass% - which is obvious to a person skilled in the art - as the density of water is around 1 g/cm³. Consequently the w/v% values according to patent specification no. US 6,372,690 referred to above can also be regarded as mass% values.)

In the patent description, unless stated otherwise, the values given in percentage relate to mass percentage and to aqueous solution. The aqueous solution can be prepared from chemically pure water or from conduit water (see below in detail).

According to a preferred embodiment of the method the spray solution is sprayed onto the plants in a direction at an angle with respect to the plane approximately perpendicular to the stem of the target plants (which plane is generally horizontal), which angle is within the angle range of ± 45°, preferably ± 30° - ± 15°. Practically the angle of the spraying direction with respect to the horizontal plane and the exit height of the spray solution is chosen depending on the average length of the stem of the plants to be sprayed currently and, optionally, its angle with respect to the vertical plane. Generally the stem of plants is vertical, but in certain cases young plants growing on a slope grow at right angles to the soil, and as they grow they become gradually adapted to gravitation. According to one of the most preferable embodiment of the method, the spray solution is sprayed onto the plants approximately at right angles to the stem of the target plants.

According to a further preferable embodiment of the method according to the invention, about 200-800 litres/ha, preferable 400-700 litres/ha, more preferable 500-600 litres/ha of spray solution is sprayed onto the target plants. The equipment according to the invention can be used, for example, for spraying herbicides. The equipment used for the realisation of the method has a container for accommodating the spray solution, a liquid forwarding unit, at least one nozzle and one or more pipes connecting the nozzle to the container through the liquid forwarding unit, and the equipment is based on that the equipment is constructed in a way suitable for changing the exit direction of the spray solution preferable within the angle range of about ± 45° with respect to the horizontal plane, and/or in order to control the exit direction of the spray solution the equipment is connected to the vehicle used for carrying the equipment in a way enabling the alteration of its position with respect to the vehicle.

According to a preferable embodiment of the equipment, the exit height of the spray solution can be regulated, which can be done automatically or manually by the person operating the equipment.

The weeds to be killed, such as composite weeds, especially ragweed, may occur on a given area in several different sizes. For example, the size of ragweed may vary between a few centimetres and even as much as one metre. For this reason spraying from a lateral direction according to the invention is even more efficient, that is an even greater amount of herbicide can be applied onto the plant, if the construction of the sprayer enables the regulation of the radial direction of the herbicide sprayed out through the mouth of the nozzle/nozzles. For example, if small weeds need to be killed, then spray jets directed downwards with respect to the horizontal plane are more preferable, while in the case of larger weeds spray jets directed upwards are more preferable.

From the aspect of the present invention target plants are plants that need to be covered with spray solution. Accordingly, in respect of herbicides the target plants are weeds, while in the case of spraying nutrients onto cultivated plants, the target plants are the cultivated plants.

In accordance with the present invention, the solvent used for the salt solution is first of all conduit water. Although conduit water, depending on its geographical situation, source and other characteristics, already contains different solutes in itself, such as ions - maybe even ions forming the salts preferred according to the invention -, generally their concentration in conduit water is negligible from the aspect of their osmotic effect as compared to the concentrations in the salt solution according to the invention. For this reason - as it is obvious for person skilled in the art - salt solutions that, besides the main ionic components (e.g.: potassium and chloride ions), also contain other components characteristic of conduit water (e.g.: iron, manganese, sulphate, nitrate, carbonate, etc.) in concentrations characteristic of conduit water are also within the scope of the present invention.

It is obvious for the person skilled in the art that spraying spray solutions from a lateral direction, at an adjustable angle and height according to the invention can be realised in many different ways, for example, by appropriately adjusting and/or controlling the angle of the nozzle, by appropriately adjusting and/or controlling the deflection angle plates built in the nozzle, and by appropriately adjusting and/or controlling the sprayer frame, or even by combining all these possibilities.

A preferable construction of the equipment is characterised by that the nozzle is constructed in a way that it can be turned least in the vertical plane and/or a deflection angle plate (plates) is (are) allocated to the mouth of the nozzle for changing the exit direction of the sprayed solution.

The herbicide composition according to the invention consists of the aqueous solution of one or more salts, and it is based on that it contains mainly or exclusively potassium chloride as its salt component, and the salt solution is a solution between 8% - 19%, preferably 12% -17%. Apart from potassium ion, optionally the salt solution may also contain a smaller amount of another alkaline metal, alkaline earth metal and/or earth metal as a cation, while apart from chloride ion, optionally it may also contain a smaller amount of another halogen ion, sulphate and/or phosphate.

The most preferable solution is when the salt solution is the aqueous solution of potassium chloride exclusively, as potassium chloride is environmental friendly, easy to obtain, and it can also be used as an artificial fertiliser in respect of cultivated plants growing near weeds.

It is also preferable to add a surface-active (surfactant) agent to the salt solution. The surface- active agent facilitates the spreading of the solution containing the effective agent on the surface of the target plant. Any surface-active agent the use of which is not excluded for reasons of environmental protection, plant protection and/or health protection may be used as a suitable surface-active agent.

The herbicide composition according to the invention is one of the so-called contact herbicides, which means that is an agent that must get in direct contact with the plant in order to achieve a preferable effect. Herbicides getting on or into the soil are not effective, therefore it is important to make sure that the highest possible proportion of the sprayed herbicide gets in direct contact with the surface of the target plants. This problem is answered by the spraying method from a lateral direction and by the sprayer according to the invention, with the use of which a greater proportion of the plant surface can be covered as compared to state-of-the-art vertical spraying.

If the method according to the invention is used in respect of herbicides, from the aspect of their chemical composition, in theory all salts that can generate an osmotic shock of appropriate intensity 'when sprayed onto the surface of the plant to be killed are suitable for producing a herbicide salt solution. However, if aspects of environmental protection, plant protection, health protection and cost-efficiency are also taken into consideration, the herbicide composition according to the invention, that is the salt solution mainly containing KCl is the most suitable for the realisation of the method according to the invention in respect of herbicides containing salt. Basically, osmosis is a phenomenon in the course of which on the two sides of a partition wall penetrable by water, such as a membrane or a plant cell wall, there are media with different ionic strengths, as a result of which the water flows through the partition wall towards the medium with higher ionic strength until the ionic strength of the solutions on the two sides is equalised. In respect of the present invention osmotic shock means that a salt solution with a very high ionic strength is applied onto the surface of the plant, as a result of which water comes out onto the plant surface, which makes the plant dry up practically within few hours.

The solutions of inorganic salts with the highest ionic strength containing alkaline metal, alkaline earth metal and/or earth metal as a cation, and halogen ion, sulphate and/or phosphate as an anion are the most suitable for generating an osmotic shock.

It is obvious for the person skilled in the art that in respect of the equipment according to the invention the exit direction of the spray solution can be controlled in any way according to the invention on one occasion before starting spraying, it can take place intermittently depending on the choice of the person performing spraying, or it can take place continuously depending on the monitoring of one or more parameters of the target plants and/or the configurations of the soil (e.g.: average change of height of the target plants).

In the case of using the spraying method from a lateral direction according to the invention, if there are intensive air motions, the spray mist containing the active agent may drift to more distant places, maybe to places where there are no target plants. Although under normal spraying conditions the spray drops hit the ground or the plant surface within about three metres, an appropriate curtain fitted onto the vehicle used for spraying or onto another vehicle following the spraying vehicle may provide efficient protection against drifting. Preferably such curtains should be placed about three metres from the spraying nozzles.

EXAMPLES

Example 1

The spraying tests were performed using spraying equipment with a frame width of 10 m, having a 450 litre tank, suspended on a tractor, at the end of August and at the beginning of September 2007, on ragweed growing 70-120 cm high. The results are shown in table 1.

Table 1: Spraying ragweed with a herbicide solution containing potassium chloride

The efficiency of acceptable treatments is above 90%, efficiency lower than this is not acceptable by us. The results indicate that vertical state-of-the-art spraying is efficient only when a large amount of spray solution is used (test no. 1 vs. tests no. 2 and 5). In the case of KCl solutions of the same concentration and the same amount, the horizontal (that is lateral) spraying method according to the invention provides an acceptable result (95%, test no. 4), while the vertical state-of-the-art method does not ensure acceptably efficient ragweed killing (70%, test no. 5).

The table also indicates that practically nozzles with a small mouth should be used. Although in the case of nozzles with a large mouth a good result was achieved when using 1,500 litres/ha of spray solution, but the result was not good when 750 litres/ha of spray solution was used. In the case of using nozzles with a small mouth and 600 litres/ha of spray solution, the result was acceptable only when the spraying direction was close to horizontal. It is pointed out here that in order to realise efficient weed killing 1,000 - 3,000 litres/ha of state- of-the-art salt solution (8-20% sodium chloride solution) need to be sprayed onto the area infested with ragweed, depending on the size of the given ragweed specimens. This amount of liquid is larger by about one order of magnitude than the amount used in the case of organic herbicides. When using a large amount of aqueous salt solution, the transportation costs are rather high. In the case of using the preferable KCl solution according to the invention, the spraying method from a lateral direction and the sprayer also according to the invention, it is enough to spray about 600 litres/ha of herbicide, which, besides the fact that it is less harmful to the environment than the solution containing sodium chloride, results in significantly lower transportation costs.

Spraying from a lateral direction according to the invention is preferable for killing ragweed, also because ragweed is a thin plant, that is its vertical elevation is small, which means that even if the spray solution coming from above is sprayed perfectly, the herbicide will only cover a low proportion of the surface of the target plant, which increases the chances of survival of the given weed. Spraying from a lateral direction according to the invention significantly increases the coverage of the plant surface with spray solution, that is with herbicide in the present case.

The advantage of the herbicide composition according to the invention is that generally salt solutions can be produced and used cheaply and quickly. The majority of salt solutions are harmless to humans, animals and to the environment when used in the concentrations according to the invention. No metabolites mentioned in the case of organic compounds, which are sometimes harmful, can be created. Consequently the salt solutions according to the invention can be used preferably for weed killing, for example, ragweed killing, on inhabited areas, where the majority of herbicides cannot be used for reasons of safety. It is pointed out here that the necessity of killing ragweed is the most pressing on inhabited areas, as this weed must be killed first of all because of its strong allergenic effects.

Besides the above, a further advantage of the herbicide composition especially preferred according to the invention containing exclusively potassium chloride is that in the concentration according to the invention it has a selective effect on ragweed, including developed large ragweed specimens too. Although to a smaller extent, but it also has an effect on other composite plants too. On inhabited areas ragweed can easily grow high, as these areas are generally not permanently supervised by agricultural experts. Therefore the herbicide composition according to the invention is especially useful, as it is also efficient against large flowering specimens, and with its help the allergenic flowering of ragweed can be terminated within a few hours. With the help of the method and equipment according to the invention, the composition containing KCl according to the invention is very efficient for killing ragweed on inhabited areas as mentioned above, and also for clearing the stubble remaining on cornfields or after wheat harvesting, or, for example, in the case of forest planting.

Claims

1. Method for spraying target plants with a spray solution characterised by that the spray solution is sprayed onto the plants from a lateral direction.

2. Method according to claim 1, characterised by that the spray solution is sprayed onto the plants in a direction at an angle with respect to the plane approximately perpendicular to the stem of the target plants, which plane is generally horizontal, which angle is within the angle range of ± 45°, preferably from ± 30° to ± 15°.

3. Method according to claim 2, characterised by that the spray solution is sprayed onto the plants approximately at right angles to the stem of the target plants.

4. Method according to any of claims 1 to 3, characterised by that the angle of the spraying direction with respect to the horizontal plane and optionally the exit height of the spray solution is chosen depending on the average length of the stem of the plants to be sprayed currently and optionally its angle with respect to the vertical plane.

5. Method according to any of claims 1 to 4, characterised by that about 200-800 litres/ha, preferably 400-700 litres/ha, more preferably 500-600 litres/ha of spray solution is sprayed onto the target plants.

6. Equipment for the realisation of the method according to any of claims 1 to 5, which has a container for accommodating the spray solution, a liquid forwarding unit, at least one nozzle and one or more pipes connecting the nozzle to the container through the liquid forwarding unit, characterised by that the equipment is constructed in a way suitable for changing the exit direction of the spray solution preferably within the angle range of about ± 45° with respect to the horizontal plane, and/or in order to control the exit direction of the spray solution the equipment is connected to the vehicle used for carrying the equipment in a way enabling the alteration of its position with respect to the vehicle.

7. Equipment according to claim 6, characterised by that the nozzle is constructed in a way that it can be turned least in the vertical plane and/or a deflection angle plate (plates) is (are) allocated to the mouth of the nozzle for changing the exit direction of the sprayed solution.

8. Equipment according to claim 6 or 7, characterised by that the exit height of the spray solution can be regulated automatically and/or manually.

9. Herbicide composition for killing composite weeds, especially ragweed, which consists of an 8% - 19% aqueous solution of one or more salts, characterised by that it contains mainly or exclusively potassium chloride as its salt component.

10. Herbicide composition according to claim 9, characterised by that apart from potassium ion, optionally the salt solution may also contain a smaller amount of another alkaline metal, alkaline earth metal and/or earth metal as a cation, while apart from chloride ion, optionally it may also contain a smaller amount of another halogen ion, sulphate and/or phosphate.

11. Herbicide composition according to claim 9 or 10, characterised by that the salt solution contains a surface-active agent.