Method for fire-extinguishment on hardly extinguishable burning materials

A very efficient method is proposed for extinguishment of fire involving various dangerous materials hardly fire-extinguishable by conventional methods, such as alkali metal peroxides, alkyl aluminum compounds, diketene and calcium carbide or phosphide in contact with water. The method comprises sprinkling, over the burning site of the fire, a silica-based or silica.multidot.alumina-based powder of porous particles having a specified particle diameter and a specified pore diameter, of which the content of silicon dioxide is at least 80% by weight or the total content of silicon dioxide and aluminum oxide is at least 90% by weight. When the burning material is metallic sodium or potassium, the powder sprinkled is a blend of the above mentioned silica-based powder and a powder of sodium chloride or potassium chloride, respectively, so that the fire can be extinguished more rapidly and reliably than in the use of the silica-based powder alone.

The present invention relates to a method for extinguishing fire on a 
hardly extinguishable burning material or, more particularly, relates to a 
method for extinguishing fire on alkali metal peroxides, alkyl aluminum 
compounds, diketene, calcium carbide, calcium phosphide, metallic sodium 
and potassium and the like. 
Needless to say, most of ordinary combustible materials take fire when the 
material is heated in the presence of oxygen and the temperature thereof 
has reached the so-called ignition temperature to start combustion. The 
most typical and versatile method for extinguishment of fire on burning 
materials in general is to sprinkle water, sand or a powdery fire 
extinguishing agent on the burning site or to blow off the flame by 
ejecting carbon dioxide gas. These conventional methods for fire 
extinguishment, however, are not applicable to the fire on the above 
mentioned specific dangerous materials including alkali metal peroxides, 
alkyl aluminum compounds, diketene, calcium carbide, calcium phosphide, 
metallic sodium and potassium and the like because the conventional 
methods of fire extinguishment not only are entirely ineffective for the 
purpose but also result in rather increasing the violence of the burning 
fire. Therefore, the use of the above mentioned conventional fire 
extinguishing agents must be strictly avoided in such a case. Following 
are the descriptions of the particular problems in the conventional fire 
extinguishing methods on the dangerous materials belonging to each class 
in connection with the combustion characteristics of the respective 
materials. 
(1) ALKALI METAL PEROXIDES 
An alkali metal peroxide such as sodium peroxide Na.sub.2 O.sub.2 and 
potassium peroxide K.sub.2 O.sub.2 is an unstable material and, when it is 
brought into contact with water, a violent reaction takes place between 
the peroxide and water to produce a large quantity of heat of reaction as 
well as a large volume of oxygen according to the following reaction 
equation given by taking sodium peroxide as an example so that the 
reaction proceeds explosively. Accordingly, use of water for the purpose 
of fire extinguishment must be strictly prohibited. 
EQU 2Na.sub.2 O.sub.2 +2H.sub.2 O.fwdarw.4NaOH+O.sub.2 
Further, alkali metal peroxides are decomposed also in contact with an 
organic material to promote combustion of the organic material so that, at 
any rate, alkali metal peroxideds must be handled with utmost care. 
In the extinguishment of fire on an alkali metal peroxide having the above 
mentioned reactivity, not only water as a matter of course but also other 
conventional fire extinguishing agents, e.g., ammonium phosphate powders, 
carbon dioxide gas, Halons and the like, cannot be used because these 
materials also may react with the alkali metal peroxide. Barely dry sand 
may serve for the purpose when the burning site can be completely covered 
therewith although complete fire extinguishment is a rather difficult 
matter. It should be noted also that it is an extremely difficult matter 
in practice to maintain a large stockpile of sand in a completely dry 
condition to prepare for a fire in a large scale. 
(2) ALKYL ALUMINUM COMPOUNDS 
An alkyl aluminum compound, such as trimethyl aluminum (CH.sub.3).sub.3 Al, 
triethyl aluminum (C.sub.2 H.sub.5).sub.3 Al, triisopropyl aluminum 
(iC.sub.3 H.sub.7).sub.3 Al and the like, is a colorless liquid and 
spontaneously takes fire when it is contacted with air. The reaction 
equations for the combustion of trimethyl aluminum (CH.sub.3).sub.3 Al and 
triethyl aluminum (C.sub.2 H.sub.5).sub.3 Al are as follows. 
EQU 2(CH.sub.3).sub.3 Al+12O.sub.2 .fwdarw.6CO.sub.2 +Al.sub.2 O.sub.3 
+9H.sub.2 O 
EQU 2(C.sub.2 H.sub.5).sub.3 Al+21O.sub.2 .fwdarw.12CO.sub.2 +Al.sub.2 O.sub.3 
+15H.sub.2 O 
Alkyl aluminum compounds are also highly reactive when they are in contact 
with water to cause an explosive decomposition reaction according to the 
following reaction equations taking trimethyl aluminum and triethyl 
aluminum as the examples. 
EQU (CH.sub.3).sub.3 Al+3H.sub.2 O.fwdarw.Al(OH).sub.3 +3CH.sub.4 
EQU (C.sub.2 H.sub.5).sub.3 Al+3H.sub.2 O.fwdarw.Al(OH).sub.3 +3C.sub.2 H.sub.6 
They also react violently with alcoholic compounds. 
When an alkyl aluminum compound has been set on fire, the fire can be 
extinguised with extreme difficulties by any of known methods of fire 
extinguishment. Namely, water or a water-containing fire extinguishing 
agent must not be used absolutely as is readily understood from the above 
given description of the reactivity of the compound. Further, carbon 
dioxide gas and Halons also cannot be used due to the reactivity thereof 
with the burning alkyl aluminum compound. Powdery fire extinguishing 
agents such as ammonium phosphate are also ineffective. The only measure 
to be undertaken is to sprinkle a large volume of dry sand over the 
burning site to suppress the violence of fire watching and awaiting 
exhaustion of the burning liquid under suppressed violence of fire. 
(3) DIKETENE 
Diketene C.sub.4 H.sub.4 O.sub.2 is widely used as an important 
intermediate in the synthesis of acetoacetic acid esters, acetoacetic acid 
anilide, and various kinds of medicines, dyes, germicides and antiseptics 
as well as other industrial chemicals. This compound is a liquid having a 
boiling point at 127.4.degree. C. and a low flash point at 35.degree. C. 
so that a slight increase in the temperature involves a danger of fire 
taking place in air. The compound burns violently at an elevated 
temperature or under a superatmospheric pressure according to the 
following reaction equation. 
EQU C.sub.4 H.sub.4 O.sub.2 +4O.sub.2 .fwdarw.4CO.sub.2 +2H.sub.2 O 
Diketene in itself has an intensely irritative malodor and is a strong 
lacrimator always involving a danger to cause a secondary disaster. It is 
insoluble in water so that a fire on burning diketene can hardly be 
extinguished by sprinkling water which results in merely enlarging the 
burning site. Conventional powdery fire extinguishing agents cannot be 
used against the fire on diketene because of the possible reaction between 
them. 
(4) CALCIUM CARBIDE AND CALCIUM PHOSPHIDE 
As is well known, calcium carbide and water violently react to produce 
acetylene according to the following reaction equation. 
EQU CaC.sub.2 +2H.sub.2 O.fwdarw.C.sub.2 H.sub.2 +Ca(OH).sub.2 
Acetylene gas readily takes fire and explosively burns when it is mixed 
with air in the presence of a fire source so that calcium carbide must be 
kept away from water. Moreover, calcium carbide may react with certain 
conventional fire extinguishing agents other than water. Dry sand barely 
provides a means for extinguishment but no sufficient effect of fire 
extinguishment can be expected for the same reasons as in the fire 
extinguishment on alkyl aluminum compounds. 
Calcium phosphide also reacts with water or moisture according to the 
following reaction equation to produce phosphine which may spontaneously 
take fire when it is mixed with air so that the fire may spread over any 
combustible materials in the vicinity. 
EQU Ca.sub.3 P.sub.2 +6H.sub.2 O.fwdarw.2PH.sub.3 +3Ca(OH).sub.2 
Thus, water can never be used also for extinguishment of fire on calcium 
phosphide. Conventional known fire extinguishing agents are also not 
applicable. Dry sand is barely applicable thereto although sufficient 
effects of fire extinguishment can hardly be obtained therewith. 
(5) METALLIC SODIUM AND POTASSIUM 
When metallic sodium or potassium is brought into contact with water, a 
violent reaction takes place therebetween according to the following 
reaction equations to generate a large quantity of heat and hydrogen gas. 
EQU 2Na+2H.sub.2 O.fwdarw.H.sub.2 +2NaOH 
EQU 2K+2H.sub.2 O.fwdarw.H.sub.2 +2KOH 
Once set on fire, these alkali metals continue burning in air according to 
the following reaction equations. 
EQU 4Na+O.sub.2 .fwdarw.2Na.sub.2 O 
EQU 4K+O.sub.2 .fwdarw.2K.sub.2 O 
Thus, water must never be used on an alkali metal for the purpose of fire 
extinguishment due to not only ineffectiveness but also a great increase 
in danger of fire. Carbon dioxide gas also reacts with an alkali metal so 
that the gas cannot be used as a fire extinguishing agent. Further, 
sufficient effects of fire extinguishment on alkali metals can not be 
obtained by using certain powdery fire extinguishing agents containing 
sodium chloride or sodium carbonate as the principal ingredient. 
Thus, it is eagerly desired to develop a novel and efficient method for 
fire extinguishment free from the above described problems and 
disadvantages when a dangerous material belonging to either one of the 
above described five classes has been set on fire. 
SUMMARY OF THE INVENTION 
The present invention accordingly has an object to provide a novel and 
efficient method for extinguishment of fire on a dangerous material 
belonging to either one of the above described classes. 
Thus, the method provided by the invention for extinguishment of fire on a 
dangerous material selected from the group consisting of alkali metal 
peroxides, alkyl aluminum compounds, diketene, calcium carbide and calcium 
phosphide comprises: sprinkling, over the burning site of the fire, a 
silica-based powder of porous particles containing at least 80% by weight 
of silica or a silica.alumina-based powder of porous particles containing 
at least 90% by weight of silica and alumina as a total, of which the 
porous particles have a particle diameter in the range from 5 .mu.m to 5 
mm, an apparent density in the range from 0.2 to 0.7 g/cm.sup.3 and a pore 
diameter in the range from 0.1 to 100 .mu.m. 
Further, the invention provides a method for extinguishment of fire on 
metallic sodium or metallic potassium which comprises: sprinkling, over 
the burning site of the fire, a powdery mixture of a silica-based powder 
of porous particles containing at least 80% by weight of silica, of which 
the porous particles have a particle diameter in the range from 5 .mu.m to 
5 mm, an apparent density in the range from 0.2 to 0.7 g/cm.sup.3 and a 
pore diameter in the range from 0.1 to 100 .mu.m, with admixture of a 
powder of an alkali metal chloride which is sodium chloride or potassium 
chloride when the burning alkali metal is sodium or potassium, 
respectively. 
The effectiveness of the above defined method of fire extinguishment can be 
further enhanced when the silica-based or silica.alumina-based powder of 
porous particles and/or the powdery sodium or potassium chloride is 
treated with an organosilane compound or an organopolysiloxane compound so 
as to be rendered hydrophobic on the surface of the particles. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As is known, the works of fire extinguishment in general are performed 
relying on four different mechanisms for extinguishment including: 
(1) the removing effect which means that the fire is ceased when the 
combustible material is removed from the burning site; 
(2) the suffocating effect which means that the burning site is shielded 
from the access of air or oxygen which supports burning of the combustible 
material; 
(3) the cooling effect which means that combustion of a combustible 
material is suppressed or discontinued when the heat of combustion is 
absorbed from or removed out of the burning system so as to decrease the 
temperature of the burning material below the ignition point thereof; and 
(4) the suppressing effect which means that the chain-like reaction of 
combustion is interrupted so as to retard propagation of fire. 
Naturally, fire extinguishing works in general mostly rely not on only one 
but on a combination of two or more of these principles so as to obtain a 
synergistic effect. The method of the invention also has been developed 
from the standpoint of obtaining an exquisite synergistic effect of these 
four different principles. 
In the first aspect of the inventive method directed to extinguishment of 
fire on a dangerous material selected from the group consisting of alkali 
metal peroxides, alkyl aluminum compounds, diketene, calcium carbide and 
calcium phosphide, the fire extinguishing agent sprinkled over the burning 
site of the fire is a specific silica-based powder or silica.alumina-based 
powder. The silica-based powder contains at least 80% by weight of silica 
and has the properties specified above. Such a specific silica-based 
powder can be obtained from a natural amorphous siliceous sand occurring 
in the Itoigawa district, Niigata Prefecture, Japan and supplied under a 
tradename of Silton 3S. To be more suitable for use in the inventive 
method, the sand of Silton 3S as supplied is mulled with water, dried and 
calcined and, after a treatment with hydrochloric acid, again dried and 
subjected to screening for particle size classification. The thus prepared 
powder is insoluble in acids and alkalis and typically has a true density 
of 2.3 g/cm.sup.3, apparent density of 0.55 g/cm.sup.3 and porosity of 70% 
and contains about 89.1% by weight of silica. 
Another fire extinguishing agent used in the inventive method alternatively 
to the above described silica-based powder is a silca.alumina-based powder 
having the above specified properties. The powder should contain at least 
90% by weight of silica and alumina as a total. Such a 
silica.alumina-based powder of porous particles can be prepared, for 
example, by blending the above mentioned Silton 3S with kaolin, mulling 
the powdery blend with water, drying, calcining, pulverizing and 
screening. This powder is also insoluble in acids and alkalis and 
typically has a true density of 2.5 g/cm.sup.3, apparent density of 0.45 
g/cm.sup.3 and porosity of 80% and contains about 68% by weight of silica 
and 23% by weight of alumina to give 91% by weight of a total of these two 
constituents. 
It is important that the particles of the above described powders have a 
particle diameter of at least 5 .mu.m or, preferably, in the range from 5 
.mu.m to 5 mm. A powder having a particle diameter not exceeding 200 .mu.m 
is suitable for use as a filling in fire-extinguishers to be ejected with 
a pressurized gas while a powder having a particle diameter exceeding 200 
.mu.m is suitable for sprinkling by using shovels, buckets and the like. A 
powder having a particle diameter smaller than 5 .mu.m or having an 
apparent density smaller than 0.2 g/cm.sup.3 is not suitable for use in 
the inventive method since the powder as sprinkled over the burning site 
of fire is readily blown off and scattered away by the violence of the 
fire. 
The powder of porous particles should have a pore diameter in the range 
from 0.1 to 100 .mu.m. In this regard, conventional silica gels, alumina 
gels and silica.alumina gels cannot be used in the inventive method since 
the pores in these gel materials distribute only in the surface layer of 
the particles and the pore diameter therein is so fine as to be 0.1 .mu.m 
or smaller exhibiting a so large surface area available for the adsorption 
of a burning liquid material such as the alkyl aluminum compounds and 
diketene as the objective dangerous material in the inventive method 
resulting in evolution of a large quantity of heat of adsorption leading 
to an increase in the temperature rather to increase the difficulty in 
fire extinguishment. 
Besides the above mentioned limitation in the purity of the powder relative 
to the content of silica and/or alumina, it is of course important that 
the powdery material used in the inventive method has a purity as high as 
possible or contains impurities which may react with the burning dangerous 
materials in an amount as small as possible. Such undesirable impurities 
include, for example, iron oxide Fe.sub.2 O.sub.3, calcium oxide CaO, 
magnesium oxide MgO, potassium oxide K.sub.2 O, sodium silicate xNa.sub.2 
O.ySiO.sub.2 and the like originating in the starting raw materials. 
Needless to say, these powders should be dry as completely as possible so 
that the powders as prepared must be fully dried and stored under a 
hermetically sealed condition to exclude atmospheric moisture. 
The sodium or potassium chloride powder admixed in the powdery fire 
extinguishing agent used in the extinguishing works of fire on burning 
metallic sodium or potassium, respectively, as an auxiliary constituent 
should have a purity of at least 99% and a particle diameter in the range 
from 1 .mu.m to 200 .mu.m. It is of course that the sodium or potassium 
chloride powder must be as dry as possible. 
It is advantageous that the powdery constituents of the fire extinguishing 
agent used in the inventive method, i.e. the silica-based or 
silica.alumina-based powder of porous particles and/or the powdery sodium 
or potassium chloride, are surface-treated, in particular, when the powder 
is used as a filling of fire extinguishers with an organosilicon compound 
such as organochlorosilanes, e.g., methyl chlorosilanes and derivatives 
thereof, or organopolysiloxanes, e.g., methyl hydrogen polysiloxanes and 
derivatives thereof, so as to be rendered hydrophobic on the surface 
resulting in a decrease in the moisture absorption and improvement in the 
free-flowing characteristic as a powder. 
When the above described powdery fire extinguishing agent is sprinkled over 
the burning site on the various dangerous combustible materials in such an 
amount that the burning material is covered up with a layer of the powder, 
a rapid and reliable effect of fire extinguishment can be achieved. When 
the burning material is an alkali metal peroxide, calcium carbide or 
calcium phosphide, for example, absolutely no chemical changes take place 
in the silica-based or silica.alumina-based powder of porous particles 
sprinkled according to the first aspect of the inventive method due to the 
non-reactivity thereof with the burning material and incombustibility in 
itself. Even though no chemical changes take place in the sprinkled 
powder, the burning material is shielded from the access of the 
atmospheric air by the layer of the powder entirely covering the burning 
site so that the fire can be rapidly and reliably extinguished by the 
suffocating effect as a result of shielding from the oxygen supply. 
The behavior of the powdery fire extinguishing agent sprinkled according to 
the first aspect of the inventive method is somewhat different when the 
burning material is a liquid such as alkyl aluminum compounds and 
diketene. Although no chemical changes take place in the silica-based or 
silica.alumina-based porous powder due to the non-reactivity thereof with 
the burning material and high heat resistance and incombustibility in 
itself, the burning liquid is rapidly absorbed in the numberless pores of 
the porous particles so that the removing effect can be exhibited. The 
suffocating effect can of course be exhibited in just the same manner as 
in the extinguishment of fire on the alkali metal peroxide and the like 
mentioned above. 
The fire on metallic sodium or potassium can be extinguished more 
efficiently by the inventive method according to the second aspect in 
which the powdery fire extinguishment agent is a blend of the silica-based 
porous powder as the principal constituent and a powder of an alkali metal 
chloride such as sodium and potassium chlorides as the auxiliary 
constituent. Preferably, the alkali metal chloride is sodium chloride or 
potaddium chloride when the burning alkali metal is sodium or potassium, 
respectively. Namely, the silica contained in the sprinkled powder may 
react with the sodium or potassium oxide as the product formed by burning 
of the alkali metal to form sodium or potassium silicate according to the 
following reaction equations. 
EQU Na.sub.2 O+SiO.sub.2 .fwdarw.Na.sub.2 SiO.sub.3 
EQU K.sub.2 O+SiO.sub.2 .fwdarw.K.sub.2 SiO.sub.3 
Sodium or potassium silicate has a relatively low melting point and is 
readily melted and converted into a glassy form which covers the burning 
site of the alkali metal to exhibit the suffocating effect. It is noted 
that the particularly fine particles in the silica-based porous powder may 
act to temporarily enhance the violence of the flame on the burning alkali 
metal. However, this rather undesirable effect can be compensated for by 
the admixture of a powder of sodium chloride, when the burning metal is 
sodium, or potassium chloride, when the burning metal is potassium, in the 
powdery fire extinguishing agent. Namely, sodium or potassium chloride 
exposed to the flame at a high temperature is decomposed to form sodium or 
potassium ions, Na.sup.+ or K.sup.+, which act as a negative catalyst to 
retard the burning of the alkali metal, i.e. sodium or potassium, so that 
the flame can be efficiently suppressed. Incidentally, sodium and 
potassium chlorides are absolutely non-reactive with metallic sodium 
and/or potassium. Thus, a synergistic effect is exhibited by sprinkling 
the composite powdery fire extinguishing agent according to the second 
aspect of the inventive method on the burning alkali metals as a 
combination of the suffocating effect by the glassy crust layer of the 
alkali silicate as a reaction product of the silica and the combustion 
product of the alkali metal and the suppressing effect by the sodium or 
potassium ions. 
The metallic sodium or potassium in the burning site is of course in a 
molten state. Although the molten sodium and potassium has a small density 
of 0.85 and 0.72 g/cm.sup.3, respectively, at 500.degree. C., the 
silica-based porous powder as the principal constituent of the powdery 
fire extinguishment agent used in the inventive method has an apparent 
density of 0.2 to 0.7 g/cm.sup.3 so that the particles never sink into but 
float on the molten alkali metal to fully exhibit the effect of fire 
extinguishment. 
In the following, the method of fire extinguishment according to the 
invention is described in more detail by way of examples.

EXAMPLE 1 
A cloth soaked with 5 ml of kerosene was spread on a stainless steel-made 
dish of 30 cm diameter and 50 g of sodium peroxide Na.sub.2 O.sub.2 were 
put thereon. The cloth wet with kerosene was set on fire. When heated at a 
high temperature, the sodium peroxide was burnt violently with orange 
flames. Thereafter, the fire was extinguished by sprinkling one of 
different fire extinguishing agents including: 
(i) a silica-based porous powder having a particle diameter distribution in 
the range from 5 .mu.m to 500 .mu.m and a pore diameter distribution in 
the range from 0.1 .mu.m to 10 .mu.m, referred to as the powder A 
hereinbelow; 
(ii) a silica.alumina-based porous powder having a particle diameter 
distribution in the range from 50 .mu.m to 5000 .mu.m and a pore diameter 
distribution in the range from 0.2 .mu.m to 100 .mu.m, referred to as the 
powder B hereinbelow; and 
(iii) conventional dry sand, referred to as the powder C hereinbelow. 
Table 1 below shows the amount of the fire extinguishing powder in g 
required for complete extinguishment of the fire and the time in seconds 
taken until complete extinguishment. 
TABLE 1 
______________________________________ 
Amount of Time taken for 
powder, extinguishment, 
Powder g seconds 
______________________________________ 
A 150 10 
B 180 12 
C 780 30 
______________________________________ 
As is understood from the results shown above, only one fourth to one fifth 
amount of the powdery fire extinguishing agent as compared with the 
conventional dry sand is sufficient according to the inventive method and 
the time taken for complete extinguishment can also be greatly decreased. 
EXAMPLE 2. 
The testing procedure was substantially the same as in Example 1 except 
that sodium peroxide was replaced with the same amount of potassium 
peroxide K.sub.2 O.sub.2. 
Table 2 below shows the amount of the fire extinguishing powder in g 
required for complete extinguishment of the fire and the time in seconds 
taken until complete extinguishment. 
TABLE 2 
______________________________________ 
Amount of Time taken for 
powder, extinguishment, 
Powder g seconds 
______________________________________ 
A 100 8 
B 130 10 
C 580 25 
______________________________________ 
As is understood from the results shown above, only one fourth to one fifth 
amount of the powdery fire extinguishing agent as compared with the 
conventional dry sand is sufficient according to the inventive method and 
the time taken for complete extinguishment can also be greatly decreased. 
EXAMPLE 3. 
As a preliminary test, 30 ml of trimethyl aluminum (CH.sub.3).sub.3 Al were 
taken in a metal-made vessel and left standing there until spontaneous 
combustion took place. The fire could easily be extinguished by sprinkling 
40 g of a silica-based porous powder having a particle diameter 
distribution in the range from 50 to 1000 .mu.m and pore diameter 
distribution in the range from 0.2 to 100 .mu.m over the fire. Then, a 
blend of 50 ml of trimethyl aluminum and 50 ml of liquid paraffin was 
taken in the same metal-made vessel as above and left standing until 
spontaneous combustion took place. The fire also could be readily 
extinguished within 60 seconds by sprinkling 30 g of the same silica-based 
porous powder as above over the burning site. 
On the other hand, the fire in a similar test for comparison failed to be 
extinguished by sprinkling 520 g of the same dry sand as used in Examples 
1 and 2. 
EXAMPLE 4. 
A 50 ml portion of triethyl aluminum (C.sub.2 H.sub.5).sub.3 Al was taken 
in a metal-made vessel and left standing there until spontaneous 
combustion took place. The fire could easily be extinguished within 70 
seconds by sprinkling 100 g of a silic.alumina-based porous powder having 
a particle diameter distribution in the range from 20 .mu.m to 2000 .mu.m, 
pore diameter distribution in the range from 0.2 .mu.m to 100 .mu.m and 
apparent density of 0.45 g/cm.sup.3 over the fire. 
For comparison, 550 g of dry sand were sprinkled over the burning site of 
triethyl aluminum to fill up the metal-made vessel without success in 
extinguishing the fire. 
As is understood from the above given Examples 3 and 4, the method of the 
present invention is very effective in rapidly extinguishing the fire on 
alkyl aluminum compounds which can hardly be extinguished with any 
conventional fire extinguishing agents. It should be noted that the 
trimethyl aluminum and triethyl aluminum used in these examples are 
notorious in the difficulty of fire extinguishment among alkyl aluminum 
compounds and the fire on other alkyl aluminum compounds of which the 
alkyl groups have three or more carbon atoms can be more easily and 
rapidly extinguished according to the inventive method. The inventive 
method is of course applicable to extinguishment of the fire on alkyl 
indium compounds, alkyl gallium compounds and the like having less 
combustibility than alkyl aluminum compounds. 
EXAMPLE 5. 
A 50 ml portion of diketene was taken in a small stainless steel-made 
vessel and set on fire. After allowing the diketene for burning for 20 
seconds, 40 g of a silica-based porous powder having a particle diameter 
distribution in the range from 5 .mu.m to 500 .mu.m and pore diameter 
distribution in the range from 0.1 .mu.m to 10 .mu.m were sprinkled over 
the burning diketene so that the fire could be extinguished within 15 
seconds without causing any boiling noise. The temperature of the diketene 
left in the vessel had been increased only to 55.degree. C. 
For comparison, the same test as above was repeated by using dry sand in 
place of the silica-based porous powder. The fire could be extinguished 
after 25 seconds when 270 g of the sand had been sprinkled. A noise of 
boiling was heard during this procedure. The temperature of the diketene 
left in the vessel had been increased to 60.5.degree. C. 
EXAMPLE 6. 
A stainless steel-made vessel having an inner diameter of 10 cm and a depth 
of 6 cm was charged with 50 g of calcium carbide to which 30 ml of water 
were poured to evolve acetylene gas. After 20 seconds of uncontrolled 
burning of the acetylene gas by ignition, a powdery fire extinguishing 
agent, which was one of the powders A, B and C used in Examples 1 and 2, 
was sprinkled over the burning site using a metal-made spoon to extinguish 
the fire. The results of these fire extinguishment tests were as shown in 
Table 3 below. 
TABLE 3 
______________________________________ 
Amount of Time taken for 
powder, extinguishment, 
Powder g seconds Remarks 
______________________________________ 
A 100 30 easily 
extinguished 
B 120 35 
C 650 -- not 
extinguished 
after 90 
seconds 
______________________________________ 
As is understood from the results shown above, the method of the present 
invention is very effective for extinguishing the fire of acetylene gas 
evolved from calcium carbide while conventional sand is quite ineffective 
for the purpose. 
EXAMPLE 7. 
The same experimental procedure as above was repeated except that the 
calcium carbide was replaced with the same amount of calcium phosphide and 
the evolved gas by pouring water was naturally not acetylene but phosphine 
gas. The results of the fire extinguishment tests are shown in Table 4 
given below. 
TABLE 4 
______________________________________ 
Amount of Time taken for 
powder, extinguishment, 
Powder g seconds 
______________________________________ 
A 80 15 
B 100 20 
C 550 30 
______________________________________ 
As is understood from the results shown above, the method of the present 
invention is very effective for extinguishing the fire of phosphine gas 
evolved from calcium phosphide while conventional sand is quite 
ineffective for the purpose. 
EXAMPLE 8. 
Sticks of metallic sodium weighing 50 g were put on a stainless steel-made 
frying pan having a diameter of 20 cm and heated from below with a gas 
burner so that the metallic sodium was melted and spontaneously ignited. 
At a moment when the temperature of the molten and burning metallic sodium 
had just reached 550.degree. C., a powdery fire extinguishing agent was 
sprinkled over the burning metallic sodium so that the fire could be 
extinguished. The sprinkled powder was either a silica-based powder of 
porouns particles having a particle diameter distribution in the range 
from 10 .mu.m to 200 .mu.m or a blend of the same with a powder of sodium 
chloride. Table 5 given below shows the mixing ratio of the silica powder 
and the sodium chloride powder by weight (SiO.sub.2 :NaCl), and the amount 
of the powder used for complete extinguishment of the fire as well as the 
notes relative to the enhancement of the flame, other remarks, if any, and 
overall evaluation of the effectiveness of the method given in four 
ratings of: A for excellent effectiveness; B for good effectiveness; C for 
fair effectiveness; and D for poor effectiveness. 
As is understood from the results shown in Table 5, the effectiveness of 
fire extinguishment according to the inventive method is more remarkable 
when the powdery fire extinguishing agent is a blend of the silica-based 
powder and sodium chloride powder according to the second aspect of the 
invention when the burning material is an alkasli metal in respect of 
suppression of the flames. Moreover, a hard crust is formed to cover the 
burning site of the fire when the powder blend contains a suitable amount 
of sodium chloride powder so as to further enhance the effectiveness of 
fire extinguishment. In this regard, the powdery mixture should contain 
from 10% to 40% by weight of the sodium chloride powder. 
For comparative purpose, the same fire extinguishment test was conducted by 
using conventional dry sand as the fire extinguishing agent. The result 
was that, by using a considerably large amount of the dry sand, not only 
the fire could not be extinguished but high flames were raised with 
bursting noises and sparks. 
TABLE 5 
______________________________________ 
Amount of Flame 
SiO.sub.2 : 
powder used, 
enhance- Other Overall 
NaCl g ment remarks evaluation 
______________________________________ 
10:0 80 intens C 
9:1 96 little B 
8:2 95 very little 
hard crust 
A 
formed after 
extinguishment 
7:3 90 no hard crust 
A 
formed after 
extinguishment 
6:4 100 no B 
5:5 100 no noise heard 
C 
______________________________________ 
EXAMPLE 9. 
The procedure of the fire extinguishment test was substantially the same as 
in Example 8 except that the metallic sodium was replaced with the same 
amount of metallic potassium and the powdery fire extinguishment agent was 
sprinkled when the temperature of the molten potassium metal had reached 
500.degree. C. The results of the tests were as shown in Table 6 below. 
TABLE 6 
______________________________________ 
Amount of Flame 
SiO.sub.2 : 
powder used, 
enhance- Other Overall 
KCl g ment remarks evaluation 
______________________________________ 
10:0 70 intense D 
9:1 76 a little C 
8:2 86 very little 
hard crust 
B 
formed after 
extinguishment 
7:3 82 very little 
hard crust 
B 
formed after 
extinguishment 
5:5 87 noticeable C 
with 
sparks 
(dry 650 very bursting noise 
D 
sand) remarkable 
with sparks 
______________________________________ 
As is understood from the results shown in Table 6, the effectiveness of 
fire extinguishment according to the inventuive method is more remarkable 
when the powdery fire extinguishing agent is a blend of the silica-based 
powder and potassium chloride powder according to the second aspect of the 
invention when the burning material is metallic potassium in respect of 
suppression of the flames. Moreover, a hard crust is formed to cover the 
burning site of the fire when the powder blend contains a suitable amount 
of potassium chloride powder so as to further enhance the effectiveness of 
fire extinguishment. The flame-suppressing effect obtained by using the 
powder blend of the silica-based powder and potassium chloride powder is 
noticeable when the amount of the potassium chloride powder is 10% by 
weight or larger in the powder blend and most remarkable when the content 
thereof is 30 to 40% by weight while an increase thereof over 50% by 
weight is undesirable because the flames are rather enhanced with sparks 
by sprinkling the powder blend. 
For comparative purpose, the same fire extinguishment test was conducted by 
using conventional dry sand as the fire extinguishing agent. Even by using 
a considerably large amount of the dry sand, not only the fire could not 
be extinguished but high flames were raised with cracking noises and 
sparks. It should also be noted that dry sand has a density of 
approximately 2.5 g/cm.sup.3 which is much larger than that of molten 
metallic potassium so that the sand particles as sprinkled readily sink 
into molten potassium and the fire naturally cannot by extinguished unless 
the amount of the sprinkled sand is impractically large.