US3425939A

US3425939A - Two-phase fire-extinguishing compositions

Info

Publication number: US3425939A
Application number: US436642A
Authority: US
Inventors: Jacques Juillard; Jean Claude Alleton
Original assignee: IND ET L AGRICULTURE SOC D ET
Current assignee: D'ETUDES CHIMIQUES POUR L'IND ET L'AGRICULTURE SOC; IND ET L AGRICULTURE SOC D ET
Priority date: 1964-01-31
Filing date: 1965-03-02
Publication date: 1969-02-04
Anticipated expiration: 1986-02-04
Also published as: FR85910E; BE659055A; CH447829A; GB1086583A; DE1218884B; SE309537B; LU47637A1; NL6500273A

Description

United States Patent 40 Claims ABSTRACT OF THE DISCLOSURE A general use fire-extinguishing composition comprising a saturated liquid phase and dispersed therein are undissolved particulate solids present in a concentration which increases the fire-extinguishing eifectiveness of the saturated aqueous phase. The flowability of the composition is maintained by a dispersing agent such as clay.

This invention is a continuation-in-part of copending application Ser. No. 429,666, filed Feb. 1, 1965, now

abandoned.

This invention relates to compositions useful for extinguishing fires, in particular to such compositions which are effective against dry fires (wood, paper, rags, etc.), fires of highly inflammable liquids, such as hydrocarbons, and mixed fires.

It is known that many potassium and sodium salts have useful fire extinguishing properties, and may be used either in the form of powder or in the form of an aqueous solution to fight fires. Among the extinguishing powders, alkali metal bicarbonates are very often used, but whereas they are very etfective against fires of hydrocarbons or other inflammable liquids, they have a drawback common to all fire extinguishing powders; they have but little effect against dry fires, and give only poor results against mixed fires.

To first fires of various kinds, it has already been proposed to use solutions of potassium organic salts, in particular salts of aliphatic acids containing 2 to 4 carbon atoms per molecule. These solutions are more generally useful than the powders for they are not only highly effective on dry fires, but are also successful when fighting fires of hydrocarbons or mixed fires. However, for fighting fires of hydrocarbons the quantity of extinguishing composition required is larger when using these solutions than when using powders; therefore, a larger sized apparatus, heavier and more cumbersome, must be used. This is particularly inconvenient in the case of portable extinguishers.

An object of this invention, therefore, is to provide firefighting compositions which have at one and the same time the advantages of the powders and of the solutions and are in this way of a very general use. Another object is to provide fire-extinguishing compositions which can be readily used after long storage periods.

Upon further study of the specification and claims, other objects and advantages of the present invention will become apparent.

To attain the objects of this invention, there is provided a broad inventive concept of a fire-extinguishing aqueous dispersion to saturation comprising water, fire-extinguishing means dissolved in said water, thereby forming an aqueous phase, and particulate solids dispersible in said aqueous phase, said particulate solids being present in a sufiicient concentration to increase the fire-extinguishing effectiveness of said aqueous phase.

Preferably, the fire-extinguishing composition of the present invention comprises an aqueous dispersion containing in dissolved and undissolved form at least one alkali metal salt, specifically potassium and/or sodium salts, with the provision that a potassium salt is present in at least one form. Anions of such salts include, for example, chloride, phosphates, sulfate, carbonate and/or bicarbonate.

The undissolved solids are in particulate form and maintained in suspension in an aqueous solution in equilibrium with said solid. This suspension is preferably maintained by the addition of a minor quantity of a dispersing agent.

In order to obtain the best results When fighting dry fires as well as fires of hydrocarbons or of other inflammable liquids with suspensions containing as active salt a mixture of potassium and sodium salts, this mixture must comprise at least 30%, on a weight basis, and preferably at least 50% of potassium salt (or salts). The term active salt is defined as the total quantity of salt (or salts) of potassium or potassium and sodium, and the general term alkali metal salts is used to designate either the potassium salts or the mixture of potassium and sodium salts as defined above.

Before being introduced into the suspension, the salts are subjected to particle size diminution, for example by grinding, so that substantially all the particles have a size less than 200 microns; preferably, the size of at least by weight of the particles is lower than microns, and advantageously about between 20 and 50% of the total solids has a particle size less than 44 microns. The particles can be extremely fine without presenting any drawback; still, for commercial purpose, substantially all are larger than 20 microns, which is the lower limit that can be obtained with industrial grinders without increasing the grinding costs inordinately.

In practice, grinding costs can be reduced by first preparing an aqueous solution of commercial-grade alkali metal salts, and then adding to said solution the finely ground salt to be maintained in suspension therein.

For preparing suspensions containing potassium bicarbonate, it is particularly advantageous to use bicarbonate which has been treated with an iron salt according to the process disclosed in copending application Ser. No. 330,549, filed Dec. 16, 1963, said application having a common inventor and the same assignee as this application, and now Patent 3,350,306, issued Oct. 31, 1967.

In general, the suspensions used contain from about 10 to 60 parts of undissolved active salt per 100 parts by weight of solution, and preferably from about 20 to 35 parts, for indeed it has been observed that when the suspension contains less than about 10% of active salt by weight of solution, the extinguishing power of the composition is practically equivalent to that of the solution itself, and that when the suspension contains more than 60% of active salt, by weight of solution, the flowing and spraying operations become difficult problems.

The dispersing agents used can be water-soluble salts, such as alkali metaphosphates and/or alkali metal silicates, the latter salts either remaining in the dissolved form or precipitating in form of colloidal silica according to the nature of the active salt present. Likewise, agents with little or no water solubility can be used, such as silicoaluminates, for example all the varieties of natural or synthetic clays, such as montmorillonite, bentonite, attapulgite etc., and/or magnesium carbonates. In particular more or less basic magnesium carbonate in form of extremely fine particles can be precipitated in the suspension itself by adding a water-soluble magnesium salt, preferably a magnesium halogenide, to the aqueous solution containing an alkali metal carbonate and/or bicarbonate. When the aqueous solution does not contain carbonate or bicarbonate, technical grade magnesium carbonates can be used, for example very finely divided products commonly sold as light magnesium carbonate.

As a general rule, the particle size of the dispersing agents present in the suspension must not be higher than 5 microns but it can be much less even down to colloidal dimensions.

A combined action of these various water-soluble and water-insoluble agents can also be utilized. The dispersing agents must be compatible with the ingredients of the composition and must not thicken the composition too much, so that it may be sprayed easily out of the extinguishing apparatus.

The quantity of dispersing agent required is always relatively minor and, in general, less than 100 grams of dispersant per liter of suspension is enough to obtain stable suspensions of active alkali metal salt. The quantity of compound added to obtain dispersion depends mainly on the nature of the compound used, water-soluble products being employed in relatively higher quantites than insoluble ones. Stable suspensions are obtained by using about 20 to 50 grams of alkali metal silicate or about 20 to 100 grams of magnesium halide per liter of suspension. Under the same conditions, quantities varying from to 40 g./1. of dispersing agents added in substantially insoluble form generally give very satisfactory results. In any event, it is apparent that the addition of greater or lesser amounts will nevertheless yield at least a finite degree of dispersing activity.

Owing to the addition of the aforesaid dispersing agents, the stability of the stored suspensions is sufficient to prevent the crystals of active salt from agglomerating, and their viscosity is low enough not to hinder the spraying of the composition onto a fire. The very fine particles in the suspension keep the active salt from settling or reduce its tendency to settle to such an extent that a very mild stirring will put it back into suspension. Even after a long storage period, the solids of the suspensions are still in the finely divided form which allows for a better extinction when the suspensions are applied to fires.

The fire-extinguishing suspensions disclosed in the present invention can be employed in any of the usual types of apparatus used for spraying water or projecting powders, which may be done by using gas pressure or any other means, such as a pump connected to a tank. As a general rule, any suitable type of apparatus for projecting a suspension may be used for fighting fires with these compositions.

Moreover, the fire-fighting compositions of the invention remain eifective within a wide range of temperatures. For example, extinguishing tests were performed with a suspension containing as active salt a mixture of potassium bicarbonate and carbonate to which sodium silicate had been added as dispersing agent. An extinguisher containing 8 liters of freshly prepared suspension was used to carry out 6 successive extinctions on a fire which was burning in a round pan of 0.7 m? area, containing 21 liters of essence F (mineral spirits having a boiling range from 100 to 160 C. under normal pressure). Under the same conditions, but with aged suspensions, there were attained, with a suspension previously kept for 20 days at a temperature of 45 C., 6 successive extinctions; with a suspension previously kept for 20 days at -20 C., 5 successive extinctions; and with a suspension kept for two months during the winter at normal outdoor temperature, during which period many changes in temperature ranging from l0 to C. were registered, 6 successive extinctions.

Additional additives common to prior art fire-extinguishing compositions can also be advantageously included in the compositions disclosed in the present invention, such as, for instance, wetting agents, corrosion inhibitors, substances which improve the spraying qualities, etc. It is obvious, however, that these additives, though added in minor amounts, must be compatible with the main constituents of the composition.

For example, it is possible to add to the suspensions a wetting agent such as, for example, an oxyethylene alkyl phenol, quaternary ammonium salts, or a product obtained from the condensation of ethylene oxide and a primary aliphatic amine in which the aliphatic radical contains from 8 to 22 carbon atoms, etc. Generally, 0.5 to 3% of wetting agent by weight relative to the weight of suspension is used.

A typical corrosion inhibitor for this system is a compound sold under the trademark Norust O.C. and which is a fatty amine derivative.

A small quantity of an aliphatic alcohol having a low molecular weight, for instance containing from 1 to 3 carbon atoms, can be advantageously added to the suspensions of the invention.

The addition of denatured alcohol, which is a product of a very low cost, is particularly advantageous to facilitate the spraying noticeably, and thereby improve the extinguishing effect. Quantites of alcohol ranging from about 0.5 to 5% by weight of suspension have been found to give excellent results in most cases.

Without further analysis, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be con strued as merely illustrative, and not limitative of the remainder of the specification and claims in any way whatsoever.

EXAMPLE 1 An aqueous saturated potassium chloride solution was prepared with a commercial grade salt containing KCl. To 10 liters of said solution were added 3 kg. of potassium chloride ground to a particle size of less than 104 microns, and 0.25 liter of a wetting agent (obtained by condensation of ethylene oxide with an aliphatic amine).

Extinguishing tests were performed with this freshly prepared suspension on fires of essence F (a petroleum out having a boiling range from to C. under normal pressure) burning in a round pan of 0.7 m? area. For each test, essence F was ignited, left to burn for 1 minute, and then the suspension was projected onto the fire under 8 kg./cm. pressure through a 12 liter/ minute spraying nozzle. The average time for extinguishing was 5 seconds.

EXAMPLE 2 An aqueous suspension of potassium chloride was prepared under exactly the same conditions as in Example 1, with the further addition of 10 g./l. of a swelling-type clay sold under the trademark Clarsil. The resulting suspension was stored quiescently for 3 months at outdoor temperature.

To simulate and observe the behavior of the suspension in a portable extinguisher, the suspension was poured into 'a cylindrical glass tube of 0.10 m. diameter and a height of 1.20 m., another small tube measuring 2 mm. inner diameter being inserted therein through which gas under pressure can be injected. When the tube is filled with 8 liters of the potassium chloride suspension, the column of liquid reaches a height of about 100 cm.

After remaining absolutely still for a period of 3 months, the only change observed in the appearance of the suspension was a band of clear liquid 3 cm. wide at the upper part of the suspension. By injecting carbon dioxide under 500 g./cm. pressure for 2 seconds through the small tube (thus simulating the effect obtained from the discharge of the carbon dioxide cartridge usually employed to operate portable extinguisher tanks), the suspension again became perfectly homogeneous.

The same 8 liters of suspension were then poured into an extinguishing apparatus of the usual type employed for projecting sprayed water, and put under pressure by means of a carbon dioxide cartridge containing 80 g. of CO With the contents of the extinguisher, it was possible to extinguish 4 consecutive times a gasoline fire (octane number 98) which had been left to burn for 1 minute in a round pan of 0.7 111. area.

EXAMPLE 3 First a solution was prepared by dissolving 50 kg. of technical grade potassium carbonate in 100 liters of water. To the resultant cooled solution were then added 25 kg. of potassium bicarbonate containing 2%iron sulfate, the 25 kg. being so ground that about 50% of the particles has a size less than 44 microns and 90% less than 74 microns. The mixture was kept well agitated, and then a further additions was made of 13 liters of a magnesium chloride aqueous solution containing 450 g./l. of MgCl and lastly 0.3 liter 80% ethyl alcohol.

Extinguishing tests were performed with the resulting suspension which contains potassium bicarbonate and carbonate as active salt, using the same apparatus as that of Example 2 (contents 8 liters). With the contents of one extinguisher, i.e., cylinder or tank, a fire of essence P which had been burning for 1 minute in a round pan of 1.08 m? area was extinguished twice running.

A blazing heap of Wood and rags soaked with essence F was also put out by means of another charge.

Several extinguishers filled with this same suspension were stored quiescently for one month in a refrigerator and the temperature was maintained therein at +4 C. At the end of this storage period, the test performed under identical conditions gave exactly the same extinguishing results as those obtained with the freshly prepared suspension.

EXAMPLE 4 A suspension containing potassium carbonate and bicarbonate was prepared under the same conditions as in Example 3 but with a different dispersing agent and a different additive.

The dispersing agent used Was sodium silicate. 25 cc. of a commercial sodium silicate solution (density 1.3) were added to 1 liter of suspension. A further addition of 5 cc. of a wetting agent (product obtained from the condensation of ethylene oxide and an aliphatic amine) and of 5 cc. of methyl alcohol (commercial grade), per liter of suspension, was then made.

The same type of extinguishing apparatus as in Examples 2 and 3 (contents 8 liters) Was used; an average of 8 to 10 extinctions was realized on a fire of essence P which had been 'burning for 1 minute in a round pan of 0.7 in. area.

The suspension was placed in a refrigerator and kept at C. for different periods of time, then extinguishing tests were performed under the same conditions as with the freshly prepared solution.

The table hereunder illustrates the average number of extinguishments obtained with the contents of one extinguisher (8 liters) on a fire of essence P which had been left to burn for 1 minute in a round pan of 0.7 m? area. The extinguishing operations were performed with an extinguisher coming out of a refrigerator, that is to say, with a suspension having a temperature very close to 20 C.

Time of storage Average No. of

at 20 C. (days): extinctions 6 submitted to periodical chan es of temperature, i.e., 48 hours at +45 C., then 48 hours at 20 C., and so on, for 2 months. The tests performed with the suspension having been submitted to such temperature variations gave the same results, under the same conditions, as those with the freshly prepared suspension, that is to say, 8 to 10 extinguishments on a fire of essence F of 0.7 In. area.

EXAMPLE 5 A solution was prepared by dissolving 2.5 kg. of potassium metaphosphate in 10 liters of water. To this solution were added 2 kg. of the same metaphosphate, but ground to a particle size of less than 104 microns. To this suspension, 10 g./l. of clay and 20 cc. of wetting agent were added.

8 liters of this suspension were discharged onto a burning heap of pieces of wood weighing 45 kg.; the wood was ignited by means of 1.5 liters of gasoline, left to burn for 10 minutes, and then the fire was attacked.

It was observed that 10 minutes after the flames had disappeared, the pieces of burnt wood were devoid of residual ignition.

EXAMPLE 6 10 kg. of technical grade disodium phosphate, Na HPO were introduced into 10 liters of water; then, after most of the phosphate was dissolved, 10 kg. of technical grade potassium bicarbonate ground so that 50% of the particles had a size less than 44 microns and less than 74 microns, were added. 0.5 liter of wetting agent obtained by condensation of ethylene oxide and an aliphatic amine were also added to the resulting suspension.

With 9 liters of this suspension, a fire of essence F left to burn for 1 minute in a round pan of 0.7 m? area was extinguished 4 times running. Average time for extinguishment was 4 seconds.

EXAMPLE 7 10 kg. of technical grade sodium sulfate (Na SO 10H O) were added to 40 liters of water, then after stirring so as to dissolve most of the sulfate, 10 kg. of technical grade potassium bicarbonate of the same particle size as in Example 1 were added.

1.35 kg. of sodium silicate (density 1.3) were then added to the suspension under thorough agitation, then 0.5 liter of denatured ethyl alcohol, and finally 1 liter of a Wetting agent were also added.

The resulting suspension was then poured into an extinguisher of the commercial type used for spraying water (contents 6 liters) using a cartridge containing 60 g. of C0 The apparatus has a discharge nozzle such that the time necessary to empty the extinguisher is 26 seconds with said suspension.

The apparatus filled with the suspension was used against a fire built of 15 kg. of wood in the form of small sticks of about 10 cm. length and about 1 cm. thickness, disposed within a casing made out of metal wire netting of a length of 1.50 m., a width of 0.10 m., and a height of 0.55 m. The wood was ignited by the combustion of 0.6 liter of essence F placed in a metal pan under the stack of wood. The essence F was left to burn for 3.5 minutes, the metal pan was then removed, and after another 30 seconds the fire, which was then burning fiercely, was attacked. After the apparatus had emptied, there were no more ignited spots left in the partly consumed mass.

EXAMPLE 8 15 kg. of technical grade potassium carbonate were dissolved in 30 liters of water. 7.5 kg. of sodium bicarbonate ground so that 90% of the particles had a size less than 50 microns, were added to the solution.

The resulting suspension was kept agitated while sodium silicate of 1.3 density (1.35 kg.), denatured ethyl alcohol (1 liter), and a wetting agent (0.6 liter) were added.

It took 5 seconds to extinguish a fire of domestic fuel which had been left to burn for 90 seconds in a round pan of 1.7 m? area, using a discharge nozzle spraying 0.2 l./ sec.

EXAMPLE 9 A solution was prepared by dissolving 88 kg. of technical grade potassium carbonate and 16 kg. of technical grade potassium bicarbonate in 200 liters of water at 20 C., to which was added a dispersing agent consisting of 10 kg. of water-soluble potassium metaphosphate.

To the resulting mixture, 50 kg. of technical grade p01" tassium sulfate containing 50% of K and ground to a particle size of less than 104 microns were added; then, a wetting agent consisting of 4 liters of a quaternary ammonium compound was also added.

Tests were performed with this suspension using the same apparatus as that in Example 2 (contents 8 liters). With the contents of one extinguisher, a fire of essence F left to burn for 1 minute in a round pan of 1.08 m? area was extinguished three times running. Average time for extinguishment was 5 seconds. The same results were obtained with extinguishers coming from a refrigerator, i.e., with a suspension at a temperature of about l7 C.

EXAMPLE 10 An aqueous suspension of potassium sulfate was pre pared under the same conditions as in Example 9, but using as dispersing agent 10 kg. of swelling clay and no wetting agent.

The resulting suspension was projected onto a pool of essence F of 4 m? area which had been left to burn for 1 minute. The apparatus used for projecting the suspension comprised a tank, a pump having a 17 bar dis-.

charge pressure, and a hose fitted with a spray nozzle having six 2 mm. holes and discharging 25 l./min. Under these conditions, extinguishment of the fire is instantaneous, the operator bein placed at about 3 m. from the blazing pool.

The preceding examples can be repeated with similar success, in conjunction with any of the generically or specifically described teachings of this invention. For example, magnesium bromide or fluoride or iodide can be employed instead of magnesium chloride under the same conditions. Likewise, other fire-extinguishing salts can be substituted for the ones specifically disclosed.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof can make various changes and modifications of the invention to adapt it to various usages and conditions. Consequently, such changes and modifications are properly, equitably, and intended to be, within the full range of equivalence of the following claims.

What is claimed is:

1. A fire-extinguishing aqueous dispersion, consisting essentially of water, normally solid fire-extinguishing solids dissolved to saturation in said water, thereby forming a saturated aqueous phase, and undissolved fire-extinguishing particulate solids dispersed in said saturated aqueous phase, said undissolved particulate solids being in equilibrium with said saturated aqueous phase, and being present in a sufficient concentration to increase the fire-extinguishing effectiveness of said saturated aqueous phase, said particulate solids having a particle size of less than about 200 microns, and said concentration being about 10-60% by weight based on the saturated aqueous phase.

2. A fire-extinguishing aqueous dispersion as defined by claim 1, further comprising a minor quantity of an inorganic dispersing agent having a particle size of not more than 5 microns and capable of maintaining said particulate solids in a substantially nonsettling state over prolonged storage periods.

3. A fire-extinguishing aqueous dispersion, comprising water and an alkali metal salt selected from the group consisting of chlorides, phosphates, sulfates, carbonates, bicarbonates, and mixtures thereof with the provisions that at least a percentage of said alkali metal salt is a potassium salt; that a portion of said alkali metal salt is dissolved in said water, thereby forming an aqueous phase; and that another portion of said alkali metal salt is suspended in the aqueous dispersion in the form of undissolved fire-extinguishing particulate solids which are present in a sufficient concentration to increase the fireextinguishing effectiveness of said aqueous phase, said particulate solids having a particle size of less than about 200 microns, and said concentration being about 1060% by weight based on the saturated aqueous phase.

4. A fire-extinguishing aqueous dispersion as defined by claim 3, further comprising a minor quantity of an inorganic dispersing agent having a particle size of not more than 5 microns and capable of maintaining said particulate solids in a substantially nonscttling state over prolonged storage periods.

5. A fire-extinguishing aqueous dispersion as defined by claim 3, wherein the water is saturated with said alkali salt, and wherein at least 30% of the total alkali metal salt is a potassium salt.

6. A fire-extinguishing aqueous dispersion as defined by claim 3, wherein the water is saturated with said alkali salt, and wherein at least 50% of the total alkali metal salt is a potassium salt.

7. A fire-extinguishing aqueous dispersion as defined by claim 3, wherein the concentration of said undissolved particulate solids in a substantially nonscttling state over phase.

8. A fire-extinguishing aqueous dispersion as defined by claim 5, wherein the concentration of said undissolved particulate solids is 20-35% by weight of the aqueous phase.

9. A fire-extinguishing aqueous dispersion as defined by claim 4, wherein said dispersing agent is selected from the group consisting of alkali metal silicates, alkali metal metaphosphates, magnesium carbonates, and silicoaluminum clays.

10. A fire-extinguishing aqueous dispersion as defined by claim 5, further comprising a minor quantity of an inorganic dispersing agent having a particle size of not more than 5 microns and capable of maintaining said particulate solids in a substantially nonscttling state over prolonged storage periods, said dispersing agent being selected from the group consisting of alkali metal silicates, alkali metal metaphosphates, magnesium carbonates, and silicoaluminum clays.

11. A fire-extinguishing aqueous dispersion as defined by claim 7, further comprising a minor quantity of an inorganic dispersing agent having a particle size of not more than 5 microns and capable of maintaining said particulate solids in a substantially nonscttling state over prolonged storage periods, said dispersing agent being selected from the group consisting of alkali metal silicates, alkali metal metaphosphates, magnesium carbonates, and silicoaluminum clays.

12. A fire-extinguishing aqueous dispersion as defined by claim 8, further comprising a minor quantity of an inorganic dispersing agent having a particle size of not more than 5 microns and capable of maintaining said particulate solids in a substantially nonscttling state over prolonged storage periods, said dispersing agent being selected from the group consisting of alkali metal silicates, alkali metal metaphosphates, magnesium carbonates, and silicoaluminum clays.

13. A fire-extinguishing aqueous dispersion as defined by claim 9, wherein said dispersing agent is present in a concentration of not more than about g. per liter of total aqueous dispersion.

14. A fire-extinguishing aqueous dispersion as defined by claim 10, wherein said dispersing agent is an alkali metal silicate present in a concentration of about 20 to 50 g. per liter of total aqueous dispersion.

15. A fire-extinguishing aqueous dispersion as defined by claim 4, wherein said alkali metal salt is selected from the group consisting of carbonates, bicarbonates and mixtures thereof and said dispersing agent is a magnesium carbonate precipitated in situ by adding a magnesium halogenide in a concentration of about 20 to 100 g. per liter of total aqueous dispersion.

16. A fire-extinguishing aqueous dispersion as defined by claim 9, wherein the dispersing agent is a waterinsoluble material having a particle size of less than microns and is present in a concentration of 10-40 g. per liter of total aqueous dispersion.

17. A fire-extinguishing aqueous dispersion as defined by claim 1, wherein about at least 90% of said undissolved fire-extinguishing particulate solids have a particle size of less than about 100 microns.

18. A fire-extinguishing aqueous dispersion as defined by claim 3, wherein about at least 90% of said undissolved fire-extinguishing particulate solids have a particle size of less than about 100 microns.

19. A fire-extinguishing aqueous dispersion as defined by claim 9, wherein at least about 90% of said undissolved fire-extinguishing particulate solids have a particle size of less than 200 microns.

20. A fire-extinguishing aqueous dispersion as defined by claim 19, further comprising a minor quantity of a monohydric alcohol of 1-3 carbon atoms.

21. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 1.

22. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 2.

23. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 3.

24. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 4.

25. A method of extinguishing fires, which method com-prises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 5.

26. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 6.

27. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 7.

28. A method of extinguishing fires, which method 10 comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 8.

29. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 9.

30. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 10.

31. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 11.

32. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 12.

33. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 13.

34. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 14.

35. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 15.

36. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 16.

37. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 17.

38. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 18.

39. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 19.

40. A method of extinguishing fires, which method comprises the step of applying to a fire a fire-extinguishing aqueous dispersion as defined by claim 20.

References Cited UNITED STATES PATENTS 3,179,589 4/1965 Lobos 252-7 3,214,372 10/1965 Lobos 252-7 3,274,105 9/1966 Meuel 252-2 FOREIGN PATENTS 645,105 7/1962 Canada.

MAYER WEINBLA'IT, Primary Examiner.

US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,425,939 February 4, 1969 Jacques Juillard et all.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 43, "first" should read fight line 67, cancel "to saturation and insert the same after "dissolved" in line 68, same column 1. Column 5 line 12, "additions" should read addition Column 8, line 26, "alkali salt should read alkali metal salt line 30, "alkali salt" should read alkali metal salts lines 34 and 35, cancel "in a substantially nonsettling state over phase. and insert is 20-35% by weight of the aqueous phase. Column 9, line 28, "less than 200" should read about Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents