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Патент USA US3072523

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United States Patent O??ce
Patented Jan. 8, 1963 a
and the formation of large lumps of undissolved and un
dispersed ammonium nitrate. Up to the present time, it
has not been convenient to prepare such gels which are
consistently homogeneous in composition and uniform
Robert E. Barnhart, Hedgesville, W. Va., and Frederick C. 5 in consistency and storage qualities. In the latter regard,
Sawyer, Hagerstown, Md., assignors to E. I. du Pont
storage for a period of 3-4 days or longer often results
de Nemours and Company, Wilmington, Del., a corpo
liquid segregation of the gel composition in the case
ration of Delaware
of the currently known gels. These gels have also gen
No Drawing. Filed Apr. 21, 1960, Ser. No. 23,641
erally been lacking in body and toughness which are de
9 Claims. (Cl. 149—2)
10 sirable for convenient loading and e?icient blasting.
It is an object of the present invention to prepare a
The present invention relates to a novel blasting agent
new gelatinous blasting agent composition. It is a further
and to a method for its preparation. More particularly,
a the present invention relates to a gelled aqueous ammoni
object of the present invention to prepare a new high ex
um nitrate blasting composition containing a high ex
plosive~sensitized gelatinous blasting composition from an
plosive sensitizer.
15 aqueous ammonium nitrate base. It is a Still further ob
ject of the present invention to prepare a new blasting
agent of the aforementioned type which is economical and
easy to manufacture and which is safe and convenient to
quarrying arts in recent years due to the relatively low
use. Other and additional objects will become apparent
cost of the ingredients of such compositions. ‘For exam
ple, prilled ammonium nitrate-fuel oil mixtures packaged 20 from a consideration of the ensuing speci?cation and
in polyethylene ‘bags and primed with suitable high ex
Broadly stated, the present invention contemplates the
plosive boosters have ‘found extensive use in many blast
preparation of a novel blasting agent by gelling a hot
ing operations. In some instances, compositions of this
aqueous ammonium nitrate liquor containing no undis
type have been poured in bulk directly into the borehole
The use of ammonium nitrate-based blasting agent
compositions has become widespread in the mining and
The ‘blasting economies which 25 solved ammonium nitrate. The gelatinous composition
of the invention also contains a high explosive sensitizer.
can be effected by means of such compositions and loading -
and successfully shot.
techniques under certain circumstances have been the
principal motivation for their extensive use.
From a
functional standpoint, however, such compositions leave
much to be desired. They do not pack the punch re 30
such as pelleted TNT, which may be added to the hot
ammonium nitrate liquor either before or after the liquor
is gelled.
The ammonium nitrate liquor employed is one which
quired for many blasting operations and, since they are
will produce ‘a ?nished product containing about 12~20%
usually loaded in plastic bags or other similar containers,
the bulk density of the blasting agent in the borehole is
often undesirably low. Much work has been done in re
monium nitrate liquor starting material containing about
60-80% by weight of ammonium nitrate.
cent years in an attempt to raise the blasting e?‘iciency
of ammonium nitrate compositions and also to raise the
bulk density of such compositions, i.e., the amount of
blasting agent which can be loaded into the borehole.
It has been proposed to prepare ammonium nitrate
about l20—180° F. and the gelling agent, such as ?nely
powdered guar gum flour, is added. The latter is dis
persed in the hot aqueous ammonium nitrate liquor by
mixing for several minutes in any suitable mixing ap
by weight of water. This corresponds to an aqueous am—
The liquor is heated to a temperature in the range of
blasting agents in slurry form, especially in an aqueous 40 paratus. Generally speaking, 10 minutes of agitation is
slurry. One such composition recently suggested is an‘
fully sui?cient
than adequate
to disperse
and inthemost
3-5 and
form a
aqueous ammonium nitrate slurry containing a pelleted
high quality uniform gel at the elevated temperatures.
trinitrotoluene (TNT) high explosive sensitizer. A dis
The high explosive sensilizer, such as pelleted TNT, may
cussion of this composition can be found in Cook, M.A.,
be added to the mixture before or after gelling or simul
“The Science of High Explosives”, ACS Monograph No.
taneously with the gelling agent, and dispersed with agi
139, published by the Rheinhold Publishing Corporation,
tation. The gel is thickened with a small amount of
New York, N.Y. (1958) page 316.
borax (sodium tetraborate) as a cross-linking agent. A
Aqueous ammonium nitrate-TNT slurries of the type
described by Cook have met with some success in the
field but their use has been limited to some extent with
more complete understanding of the present invention
ing water and with seamy boreholes. In the latter case,
Example 1
A gelatinous blasting agent composition is prepared
will be gained from a consideration of the following ex
respect to boreholes containing large amounts of stand 60 amples.
‘ a large proportion of the aqueous slurries may be carried
off out of the borehole before there is an opportunity to
from the following components:
initiate the blast. In those instances where the boreholes
contain a considerable amount of water, the concentra
75% ,ammonium nitrate liquor ______________ __ 48.95
tion of the ammonium nitrate in the borehole is reduced
Finely powdered sodium nitrate ____________ __ 25.00
considerably, thereby lowering the bulk density of the
l’elleted TNT (available as Pelletol No. 1, manu
blasting agent, perhaps even to the point where the agent
factured by E. I. du Pont de Nemours and
will not shoot.
Co.) __________________________________ __ 25.00
To overcome these de?ciencies in the aqueous am~ 60 Finely ground guar gum ?our ______________ __
monium nitrate-TNT slurries of the type described by
Cook, it has been proposed to add a gelling agent to the
_________________________ .._~ ________ __
composition to convert it from a loose ?uid slurry to a
The ammonium nitrate liquor Was heated to a tempera~
water-compatible, i.e., not affected by exposure to water 05 ture of 140° F. and loaded into a large mixing apparatus.
in ‘a borehole, and may also tend to resist leakage from
The guar gum ?our was separately mixed with the sodi
um nitrate and then added to the mixer. The resultant
the borehole through small seams and cracks.
gelatinous mass.
The resulting gel may be generally
These gel compositions, however, are slow to form,
usually requiring extensive mixing for about 30-45
minutes before a usable product is obtained. Shorter mix
ing periods usually result in non-uniform consistencies
composition was subjected to agitation in the mixer for
a period of 2-3 minutes and the pelleted TNT was there
after added. Mixing was continued for an additional 2
minutes and then the borax was added. The resultant
composition was a ?ne, even, uniform gelatinous mass
laboratory by heating.
characterized by the appearance of ?ne needle-like crys
tals of ammonium nitrate dispersed evenly throughout
and sodium nitrate were heated together to 190° F. to
dissolve most of the sodium nitrate. The guar gum ?our
was added and mixed for 2 minutes. Then the Composi
tion A and the borax were added and mixed for 1 minute.
The resultant composition at room temperature was a
the gel. The consistency of the mass‘ was very uniform
and there were no lumps of any type except for the TNT
pellets which were thoroughly distributed in the gel ma
The ammonium nitrate liquor
tough non-elastic gel resembling bread dough. The
trix. The gel was tough, elastic, and had a ?rm body.
density was 1.47 g./cc. The material shot in .1" diam
eter with a l0-gm. RDX'booster.
composition was sensitive to initiation by 100 grams of
RDX and shot with a velocity of 4500 meters per sec 10
Example 5
ond in a 5%" diameter column.
The density of the mass was 1.45 grams per cc.
A gelatinous blasting composition was prepared from
the following components:
Example 2
Following the procedure described in Example 1, a
blasting agent composition was prepared from the fol‘ 15
lowing component materials:
__________________________________ __
TNT ___
Ammonium nitrate _______________________ __
Finely ground guar gum __________________ __
20.00 20 Borax (as a 10% aqueous solution) ________ _..
75% ammonium nitrate liquor _____________ ..
Finely powdered sodium nitrate ____________ .._
Flaked TNT
Finely ground guar gum ?our _____________ .._.
____ __
Density—1.30 g. / cc.
The RDX, TNT, ammonium nitrate and water were
The physical properties of the gelatinous mass were 25 heated to 190° F. together to melt the RDX and TNT
similar to those of the product prepared in Example 1,
and dissolve the ammonium nitrate. To this hot solu
including the uniformity of the composition. ‘The prod
tion the guar gum ?our was added and mixed two
uct had a density of 1.43 grams per cc., was sensitive to
minutes. Then the borax solution was added and mixed
initiation by 100 grams of RDX, and shot at a velocity of
one minute. In 1%" diameter, the composition shot with
____ _._
3500 meters per second in a 51/2" diameter column.
a 10-gm. RDX booster. At room temperature, the com
position was a uniform gel, did not stick to a polyethylene
Example 3
A blasting agent composition was prepared from the
following components:
Percent 35
79% ammonium nitrate liquor ____________ _Finely powdered sodium nitrate ____________ .._
bag but exhibited no elasticity.
Finely ground guar gum ?our ______________ __
Example 6
A gelatinous blasting composition was prepared from
the following components:
______________________ __.
Finely ground sodium nitrate _____________ .4.
To the ammonium nitrate liquor in a suitable container
was added the dry soda and the RDX and TNT. The
resultant composition was heated at a temperature of
185-190° F. The guar gum flour was thereafter added
and mixed for a period of 3 minutes following which the
borax was added under mixing for a further 2 minutes
to thicken the gel. The resultant composition was a
The procedure followed was similar to that of Example
5. The sodium nitrate was combined with the RDX,
TNT, ammonium nitrate and water for the initial heating.
The resultant composition shot in 1%" diameter with a
characterized by the appearance of ?ne needle-like crys
tals of ammonium nitrate (visible only by microscopic
examination) dispersed evenly throughout the gel. The
Ammonium nitrate
Guar gum
?ne, uniform, gelatinous mass containing no lumps and
Borax (as a 10% aqueous solution) _________ .._
10-gm. RDX booster. At room temperature, the com
position was a uniform gel, did not stick to a polyeth
ylene bag, and exhibited good elasticity. It had a density
of 1.45 gms./cc.
TNT. and RDX were likewise dispersed uniformly
Example 7
throughout the gel matrix. There were no lumps of
any kind in the gel and the gel was a tough elastic mass
A gelatinous blasting composition was prepared from
having a ?rm body. A 250 gram sample in the form
the following components:
of a small round sphere was stretched 6-8 feet before
breaking. The composition was sensitive to initiation by 60 Flaked TNT
10 grams of RDX in a 1" diameter column.
Example 4
A gelatinous blasting composition was prepared from
the following components:
60% ammonium nitrate liquor _____________ __
Finely ground sodium nitrate ______________ _..
Granular ammonium nitrate _______________ __
Guar ?our
Borax (as a 10% aqueous solution) _________ .._
Composition A (91% RDX, 9% wax) ______ __
75% AN liquor __________________________ __
Finely powdered sodium nitrate ____________ __
Finely ground guar gum ?our ______________ __
The hot 60% liquor is pregelled for_15-20 seconds by
_____ __
70 mixing with the guar ?our. The pregelled liquor is added
to a mixer, followed by the sodium nitrate, ammonium
nitrate, TNT and borax and mixed for 1 minute. At
room temperature, this composition is soft and sticky with
moderate elasticity; but it is a good uniform gel which
Four hundred grams of this material was made in the 75 is ?rm at 40-50‘ F. and stiff at 0° F.
Example 8
A gelatinous blasting agent composition was prepared
from the following components:
Ammonium nitrate _______________________ __ 43.9
Powdered sodium nitrate __________________ __ 19.9
liquor starting material. ‘The liquor is heated to a tem
perature in the range of 120-180° F. and preferably in
the vicinity of 140—l60° F. at which temperatures the
ammonium nitrate is completely dissolved in the concen
trations used. The elevated temperatures employed are
a critical feature of the invention. If a uniform, high
quality product is to be obtained, it is important that
substantially none of the ammonium nitrate remain in
Grained 60% RDX/40% TNT composition ____ 19.9
Guar gum flour
an undissolved state. The gelling agent is then added to
10 the liquor, either alone or in admixture with ?nely pow
Borax (as a 10% aqueous solution) __________ .__ 0.03
dered sodium nitrate. The latter represents an excellent
vehicle for addition of the gelling agent and serves also
to depress the freezing point of the gelatinous end
product and to elevate the density of the composition.
In this example,‘ the RDX/TNT composition was grained
by melting 85%v of this composition with 15% paraffin 15 Sodium nitrate also contributes to the elasticity of the
product where this is desired. It is not a critical ingre
and stirring manually with a wooden paddle in a bucket
dient of the new compositions, however, and may be
until a ?ne material was formed. The ammonium ni
omitted especially where freezing temperatures are not
trate was dissolved in the water and heated to 150° F.
expected to be encountered in the ?eld.
This liquor was added to the bowl, the sodium nitrate/
Guar gum flour, a gelactomannan substance, has been
guar mixture added, and mixed 3 minutes. The grained 20
found to be an excellent gelling agent for the ammonium
RDX/TNT composition was then added, then the borax,
nitrate liquor inasmuch as its gelling ability is substan
and mixed 2 more minutes. The resultant mass shot in
tially unaffected by the presence of large amounts of
11/2” diameter with a 10-gm. RDX booster.
dissolved nitrate salts. As the gelling agent, guar gum
Example 9
25 ?our, therefore, represents the much preferred embodi
ment of the invention since it yields vastly superior re
sults compared with any other known gelling agents.
Other gelling agents are operable, however, including
Granular ammonium nitrate ______________ __ 43.9
Powdered sodium nitrate __________________ .._
locust bean ?our, and may be used in lieu of guar gum
Composition A (91% RDX, 9% wax) ______ ..
30 ?our provided that their ability to form a gel is not
Guar gum ?our _________________________ __
Borax (as a 10% aqueous solution) _______ __
materially inhibited by the nitrates in solution. In order
to achieve the full bene?ts of the invention, the gelling
agent, i.e., the guar gum ?our, must be extremely ?ne.
Coarse grades of guar gum ?our tend to require an un
Half the ammonium nitrate was dissolved in water and
heated to 150° F. This liquor was added to the mixer,
followed by the sodium nitrate/guar mixture and mixed
3 minutes, then the Composition A, the ammonium ni
desirably long amount of time for gel formation. Prefer
ably, 50% of the guar gum ?our should pass through a
325-mesh screen (U.S. Sieve Series).
Any high explosive composition may be used as a
sensitizer, including TNT, RDX, PETN, pentolite, Cyclo
trate remaining and borax solution were added and 40 tol, HBX, Torpex, tetryl, Tetratol, and the like.
mixed 2 minutes. The resultant gel composition shot in
11/2" diameter with a 10-gm. RDX booster.
Example 10
Gelatinous blasting compositions were prepared from
the following components:
Comp. X, Comp. Y, Connp. Z,
percent percent percent
positions formulated with RDX have greater sensitivity
to initiation in small diameter. However, TNT is es
pecially preferred as the sensitizer for economic reasons
and in view of its favorable safety characteristics. The
TNT may be used in any suitable particulate form which
is susceptible of dispersion in the gelatinous matrix, in
cluding for example, pelleted TNT, ?aked TNT, grained
TNT, and the like. Other high explosive sensitizers in
these forms may also be used or the sensitizer may be
Water _______________________ _-
Granular ammonium nitrate.
Sodium nitrate ______________ __
15. 07 50
added to the composition in molten form where con
35. 4
22. 1
34. 1
19. 9
24. 9
24. 9
Fine-grainpd ammonium nitrate ________________ -_
“cited TNT _________________________ __
l2. 0
________ -_
312% RDX/40% TN’l‘ composition"
'lum' gum ?our_____
liorax solution ____ __
The mixing procedure for these formulations was pregel—
ling the granular ammonium nitrate and water with guar
gum ?our and heating the “sol” to l90—l95° F. This
sol was added to the mixer, which had been warmed
with hot water, and immediately the melted TNT or
molten RDX/TNT mixture was added and dispersed in
the “sol” matrix by mixing for 1-2 minutes. The ?ne
Borax is used as the cross-linking agent for the gelling
agent. Any common commercial grade of borax may be
used, including the product available for household pur—
poses. For best and fastest dispersion, the borax is
best added to the system in aqueous solution, for example,
as a 10% aqueous solution. Adding the borax in aqueous
solution also tends to enhance the evenness and uni
formity of the cross-linking of the gelling agent. About
ODS-0.1% by weight of borax is used. based on the
weight of the fully formulated composition. Proportions
greater than this should be avoided since they may result
in degradation of the gel due to ingredient segregation.
The essential components of the novel blasting com
positions of the present invention are ammonium nitrate,
water. high explosive sensitizer, gelling agents, and a
grained ammonium nitrate and sodium nitrate were then
added, followed by the borax solution. The purpose of
the dry soda and ammonium nitrate is to cool the mix
cross-linking agent.
rapidly. Compositions Y and Z shot in 1%" diameter
nents may be present in the composition within the fol
with a 10-grn. RDX booster and Composition X shot in
21/2" diameter with the l0-gm. RDX booster.
The aqueous ammonium nitrate liquor used in the
preparation of the new blasting agent contains a per
Generally speaking, these compo
lowing proportions expressed as percentages by weight:
Ammonium nitrate ____________________ __
_______________________________ .._.
centage of water which will produce a gelatinous product
sensitizer ____________ _'.. _______________ __
containing about 12—20% water. As noted above, this
Gelling agent _________________________ .__ 0.5- 1.5
corresponds to a 60—80% aqueous ammonium nitrate 75 Cross-linking agent ____________________ .. 0.05-- 0.1
In addition, up to one-half of the ammonium nitrate in
the composition may be replaced by sodium nitrate.
The novel gelatinous blasting agent compositions of
The gelatinous blasting agents of the present invention
may be loaded directly into the borehole along with suit
able primers and conventional initiating means. One con
venient arrangement is to package the blasting agent in
and uniform consistency. In the product, much of the CI plastic bags, such as polyethylene, which are slit at the
blasting site and dropped into the borehole. Since the
ammonium nitrate remains in solution in the !wet gel; the
the present invention are characterized by a very ?ne
remainder crystallizing out in the form of ?ne, uniform,
density of the gel compositions is signi?cantly greater
evenly-dispersed, needle-like crystals of microscopic size.
than that of water, the bagged product will sink to the
bottom of the borehole even in holes containing standing
The composition is free from lumps of any kind except
for the high explosive sensitizer itself when the latter is 10 . water. Nor will the latter have any material e?ect on
the gelatinous compositions. Due to its gelatinous plastic
in a solid particulate form. The new compositions are,
nature, the composition will ooze from the bag containers
in general, tough,-elastic compositions of ?rm body, as
through the slits. The weight of the blasting column over
more particularly described below, which tend to hold
head will cause the gel to leave the bags through the
their shape but which will undergo moderate plastic ?ow
slits at a suitably fast rate'so that the gelatinous composi
in the borehole to completely ?ll the borehole. The extent
tion will substantially ?ll the borehole regardless of its
of plastic ?ow which these compositions exhibit, however,
internal con?guration. Even irregular holes will be sub
is not generally so severe as to permit the compositions
to run quickly out of the borehole into seams, cracks, or
stantially completely ?lled thus insuring the maximum
possible loading density of blasting agent in the borehole.
crevices which may be present.
The physical nature and consistency of the new gela~ 20 On the other hand, the rate of plastic ?ow of the new
compositions is not so great that any substantial amount
tinous blasting agents will vary somewhat from case to
of composition will be dissipated in the boreholes due to
case depending upon the precise formulation in each in
escape via scams or cracks in the walls of the borehole
stance. Generally speaking, this is advantageous since
prior to initiation of the blasting agent.
it permits “tailoring” the composition to the job to be
The new blasting agents of the present invention and
done, i.e., the physical properties of the composition may
their method of manufacture have been disclosed in the
be adjusted to some extent in accordance with anticipated
foregoing speci?cation. It will be readily apparent to
?eld conditions where the composition is expected to_ be
those skilled in the art that many variations may be made
used. Since temperature has a profound effect on the
in the compositions and procedures described without
consistency of the products, compositions to be used in
warm or hot climates will desirably be tough and ta?y 30 varying from the spirit of the present invention. It is,
therefore, intended to be limited only by the following
like to hard at ordinary room temperature, i.e. tempera
tures in the vicinity of 70° F. Such compositions will
We claim:
be quite hard at 40°—50° F., but will be plastic and work
able at 90 °-l00° F.’ The products prepared in Examples
4 and 5 are illustrative of such compositions. Composi
tions intended to be used in cold climates, on the other
hand, where temperatures are likely to be near or below
freezing will desirably be much less viscous at room tem
1. A blasting agent composition consisting essentially
of a uniform dispersion of ?ne needle-like crystals of
ammonium nitrate and a dispersed high explosive sensi
tizer in a tough, elastic, gelatinous mass formed by
thoroughly mixing a gelling agent selected from the group
consisting of guar gum ?our and locust bean ?our, the
such compositions will generally appear much like a ?rm, 40 sensitizer, and sodium tetraborate as a cross-linking agent
for the gelling agent into a hot aqueous solution of am
friable rubber. A composition of this type is illustrated
monium nitrate containing no undissolved salt at a tem
by the product of Example 7. In general, the substitution
perature in the range of about 120°—180° F., said com
in the formulation of sodium nitrate for ammonium ni
position containing by weight 30-60% ammonium ni
trate, within the prescribed limits, tends to increase vis
trate, 12-20% water, 15-30% high explosive sensitizer,
cosity and increase elasticity of the composition at room
0.5—l.5% gelling agent, and 0.05—0.1% sodium tetra
By using the hot aqueous ammonium nitrate liquor con
2. A blasting agent composition as in claim 1 in which
taining no undissolved ammonium nitrate as the starting
a portion of the ammonium nitrate is replaced by sodium
material, it is possible to prepare a ?ne, uniform gel upon
perature, i.e., toothpaste-like in consistency. At 0° R,
addition of the gelling agent in a matter of a few minutes,
usually no more than 3-5 minutes, and this represents a
distinct advantage from the manufacturing standpoint.
Prior art techniques for preparing gel compositions of this
general type at room temperature have invariably required
3. A process for the manufacture of a gelatinous blast~
ing agent of the type de?ned in claim 1 comprising heat
ing an aqueous ammonium nitrate liquor to a tempera
much more extensive mixing, along the order of 30-45
ture in the range of l20°-180° F., thoroughly mixing
the hot aqueous ammonium nitrate liquor with a high
minutes at a minimum.
explosive sensitizer, a gelling agent and borax as a cross
By means of the manufacturing
linking agent for the gelling agent to form a ?ne, uniform
gel in which the ammonium nitrate is evenly and uni
economies are effected in the cost of manufacturing the
formly dispersed, the ratio of ammonium nitrate to water
new blasting agent.
In the foregoing description of the preparation of the 60 in the aqueous ammonium nitrate liquor starting mate
rial being such that at the temperatures speci?ed no sub
new gelatinous blasting compositions, the preferred orders
stantial amount of the ammonium nitrate remains in the
of the addition of the component materials has been in
technique of the present invention, substantial operating
dicated inasmuch as these methods of manufacture gen
undissolved state.
4. A process as in claim 3 wherein the aqueous am
erally lead to the highest quality, most uniform gel prod
ucts. It is possible, however, to prepare blasting gels 65 monium nitrate is heated to a temperature in the range
of 140°—l60° F.
within the scope of the present invention by mixing the
S. In the process of manufacturing a gelatinous blast
ingredients speci?ed in other ways and in di?erent orders
ing agent of the type de?ned in claim 1, the novel steps
than those described, and the invention is not limited to
any speci?c order of addition. The use of a hot am
monium nitrate liquor containing no undissolved am
monium nitrate and heated to the temperatures speci?ed,
on the other hand, does represent a critical feature of the
of heating an aqueous ammonium nitrate liquor to a
70 temperature in the range of 120°—l80° F. and adding to
said hot aqueous ammonium nitrate liquor, a gelling
agent selected from the group consisting of guar gum
?our and locust bean flour and sodium tetraborate as a
invention inasmuch as the superior gelatinous blasting
cross-linking agent therefor.
agents of the present invention cannot be obtained in any
6. A process as in claim 5 wherein the aqueous am
other way.
monium nitrate is heated to a temperature in the ran
after slitting the bag-like containers in order to facilitate
of 140°-160° F.
egress of the contents of the bag in the borehole, and
7. A process as in claim 6 wherein the hot aqueous amthereafter detonating the charge.
monium nitrate liquor is dynamically mixed with the
gelling agent for a period of not more than 10 minutes. 5
References Cited in the ?le Of this Patent
8. A blasting agent as in claim 1 packaged in bagUNITED STATES PATENTS
like containers.
9- A blasting process which comprises drilling a bore
11010 In the materlal to be blasted, loading therein a
charge of blasting agent of the type de?ned by claim 8 10
glazed-5 ------------- -
Davidson ____________ “ oct- 23:
Z, 1956
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