In another building (No. 21), is a well-equipped chemical laboratory for
chemical analyses and investigations of explosives, structural
materials, and fuels.
Several months were required to calibrate the various apparatus, and to
make analyses of the available natural gas to determine the correct
method of proportioning it with air, so as to produce exact mixtures of
2, 4, 6, or 8% of methane with air. Tests of existing explosives were
made in air and in inflammable mixtures of air and gas, with a view to
fixing on some standard explosive as a basis of comparison. Ultimately,
40% nitro-glycerine dynamite was adopted as the standard. Investigative
tests having been made, and the various factors concerning all the
explosives on the market having been determined, a circular was sent to
all manufacturers of explosives in the United States, on January 9th,
1909, and was also published in the various technical journals, through
the associated press, and otherwise.
On May 15th, 1909, all the explosives which had been offered for test,
as permissible, having been tested, the first list of permissible
explosives was issued, as given in the following circular:
“EXPLOSIVES CIRCULAR NO. 1.
“DEPARTMENT OF THE INTERIOR.
“United States Geological Survey.
“May 15, 1909.
“LIST OF PERMISSIBLE EXPLOSIVES.
“Tested prior to May 15, 1909.
“As a part of the investigation of mine explosions authorized by
Congress in May, 1908, it was decided by the Secretary of the Interior
that a careful examination should be made of the various explosives
used in mining operations, with a view to determining the extent to
which the use of such explosives might be responsible for the
occurrence of these disasters.
“The preliminary investigation showed the necessity of subjecting to
rigid tests all explosives intended for use in mines where either gas
or dry inflammable dust is present in quantity or under conditions
which are indicative of danger.
“With this in view, a letter was sent by the Director of the United
States Geological Survey on January 9, 1909, to the manufacturers of
explosives in the United States, setting forth the conditions under
which these explosives would be examined and the nature of the tests
to which they would be subjected.
“Inasmuch as the conditions and tests described in this letter were
subsequently followed in testing the explosives given in the list
below, they are here reproduced, as follows:
“(1) The manufacturer is to furnish 100 pounds of each explosive which
he desires to have tested; he is to be responsible for the care,
handling, and delivery of this material at the testing station on the
United States arsenal grounds, Fortieth and Butler streets, Pittsburg,
Pa., at the time the explosive is to be tested; and he is to have a
representative present during the tests, who will be responsible for
the handling of the packages containing the explosives until they are
opened for testing.
“(2) No one is to be present at or to participate in these tests
except the necessary government officers at the testing station, their
assistants, and the representative of the manufacturer of the
explosives to be tested.
“(3) The tests will be made in the order of the receipt of the
applications for them, provided the necessary quantity of the
explosive is delivered at the plant by the time assigned, of which due
notice will be given by the Geological Survey.
“(4) Preference will be given to the testing of explosives that are
now being manufactured and that are in that sense already on the
market. No test will be made of any new explosive which is not now
being manufactured and marketed, until all explosives now on the
market that may be offered for testing have been tested.
“(5) A list of the explosives which pass certain requirements
satisfactorily will be furnished to the state mine inspectors, and
will be made public in such further manner as may be considered
desirable.
“TEST REQUIREMENTS FOR EXPLOSIVES.
“The tests will be made by the engineers of the United States
Explosives Testing Station at Pittsburg, Pa., in gas and dust gallery
No. 1. The charge of explosive to be fired in tests 1, 2, and 3 shall
be equal in disruptive power to one-half pound (227 grams) of 40 per
cent. nitroglycerin dynamite in its original wrapper, of the following
formula:
Nitroglycerin 40
Nitrate of sodium 44
Wood pulp 15
Calcium carbonate 1
---
100
“Each charge shall be fired with an electric fuse of sufficient power
to completely detonate or explode the charge, as recommended by the
manufacturer. The explosive must be in such condition that the
chemical and physical tests do not show any unfavorable results. The
explosives in which the charge used is less than 100 grams (0.22
pound) will be weighed in tinfoil without the original wrapper.
“The dust used in tests 2, 3, and 4 will be of the same degree of
fineness and taken from one mine.[6]
[Footnote 6: With a view to obtaining a dust of uniform purity and
inflammability.]
“TEST 1.--Ten shots with the charge as described above, in its
original wrapper, shall be fired, each with 1 pound of clay tamping,
at a gallery temperature of 77° F., into a mixture of gas and air
containing 8 per cent. of methane and ethane. An explosive will pass
this test if all ten shots fail to ignite the mixture.
“TEST 2.--Ten shots with charge as previously noted, in its original
wrapper, shall be fired, each with 1 pound of clay tamping at a
gallery temperature of 77° F., into a mixture of gas and air
containing 4 per cent. of methane and ethane and 20 pounds of
bituminous coal dust, 18 pounds of which is to be placed on shelves
laterally arranged along the first 20 feet of the gallery, and 2
pounds to be placed near the inlet of the mixing system in such a
manner that all or part of it will be suspended in the first division
of the gallery. An explosive will pass this test if all ten shots fail
to ignite the mixture.
“TEST 3.--Ten shots with charge as previously noted, in its original
wrapper, shall be fired, each with 1 pound of clay tamping at a
gallery temperature of 77° F., into 40 pounds of bituminous coal dust,
20 pounds of which is to be distributed uniformly on a horse placed in
front of the cannon and 20 pounds placed on side shelves in sections
4, 5, and 6. An explosive will pass this test if all ten shots fail to
ignite the mixture.
“TEST 4.--A limit charge will be determined within 25 grams by firing
charges in their original wrappers, untamped, at a gallery temperature
of 77° F., into a mixture of gas and air containing 4 per cent. of
methane and ethane and 20 pounds of bituminous coal dust, to be
arranged in the same manner as in test 2. This limit charge is to be
repeated five times under the same conditions before being
established.
“NOTE.--At least 2 pounds of clay tamping will be used with
slow-burning explosives.
“Washington, D.C., _January 9, 1909_.
“In response to the above communication applications were received
from 12 manufacturers for the testing of 29 explosives. Of these
explosives, the 17 given in the following list have passed all the
test requirements set forth, and will be termed permissible
explosives.
“_Permissible explosives tested prior to May 15, 1909._
----------------------------+----------------------------------------
Brand. | Manufacturer.
----------------------------+----------------------------------------
Ætna coal powder A | Ætna Powder Co., Chicago, Ill.
Ætna coal powder B | Do.
Carbonite No. 1 | E. I. Dupont de Nemours Powder Co.,
| Wilmington, Del.
Carbonite No. 2 | E. I. Du Pont de Nemours Powder Co.,
| Wilmington, Del.
Carbonite No. 3 | Do.
Carbonite No. 1 L. F. | Do.
Carbonite No. 2 L. F. | Do.
Coal special No. 1 | Keystone Powder Co., Emporium, Pa.
Coal special No. 2 | Do.
Coalite No. 1 | Potts Powder Co., New York City.
Coalite No. 2 D | Do.
Collier dynamite No. 2 | Sinnamahoning Powder Co., Emporium, Pa.
Collier dynamite No. 4 | Do.
Collier dynamite No. 5 | Do.
Masurite M. L. F. | Masurite Explosive Co., Sharon, Pa.
Meteor dynamite | E. I. Du Pont de Nemours Powder Co.,
| Wilmington, Del.
Monobel | Do.
----------------------------+----------------------------------------
“Subject to the conditions named below, a permissible explosive is
defined as an explosive which has passed gas and dust gallery tests
Nos. 1, 2, and 3 as described above, and of which in test No. 4 1½
pounds (680 grams) of the explosive has been fired into the mixture
there described without causing an ignition.
“_Provided:_
“1. That the explosive is in all respects similar to the sample
submitted by the manufacturer for test.
“2. That double-strength detonators are used of not less strength than
1 gram charge consisting by weight of 90 parts of mercury fulminate
and 10 parts of potassium chlorate (or its equivalent), except for the
explosive ‘Masurite M. L. F.’ for which the detonator shall be of not
less strength than 1½ grams charge.
“3. That the explosive, if in a frozen condition, shall be thoroughly
thawed in a safe and suitable manner before use.
“4. That the amount used in practice does not exceed 1½ pounds (680
grams) properly tamped.
“The above partial list includes the permissible explosives that have
passed these tests prior to May 15, 1909. The announcement of the
passing of like tests by other explosives will be made public
immediately after the completion of the tests for such explosives.
“A description of the method followed in making these and the many
additional tests to which each explosive is subjected, together with
the full data obtained in each case, will be published by the Survey
at an early date.
“NOTES AND SUGGESTIONS.
“It may be wise to point out in this connection certain differences
between the permissible explosives as a class and the black powders
now so generally used in coal mining, as follows:
“(_a_) With equal quantities of each, the flame of the black powder is
more than three times as long and has a duration three thousand to
more than four thousand times that of one of the permissible
explosives, also the rate of explosion is slower.
“(_b_) The permissible explosives are one and one-fourth to one and
three-fourths times as strong and are said, if properly used, to do
twice the work of black powder in bringing down coal; hence only half
the quantity need be used.
“(_c_) With 1 pound of a permissible explosive or 2 pounds of black
powder, the quantity of noxious gases given off from a shot averages
approximately the same, the quantity from the black powder being less
than from some of the permissible explosives and slightly greater than
from others. The time elapsing after firing before the miner returns
to the working face or fires another shot should not be less for
permissible explosives than for black powder.
“The use of permissible explosives should be considered as
supplemental to and not as a substitute for other safety precautions
in mines where gas or inflammable coal dust is present under
conditions indicative of danger. As stated above, they should be used
with strong detonators; and the charge used in practice should not
exceed 1½ pounds, and in many cases need not exceed 1 pound.
“Inasmuch as no explosive manufactured for use in mining is flameless,
and as no such explosive is entirely safe under all the variable
mining conditions, the use of the terms ‘flameless’ and ‘safety’ as
applied to explosives is likely to be misunderstood, may endanger
human life, and should be discouraged.
“JOSEPH A. HOLMES,
“_Expert in Charge Technologic Branch_.
“Approved, May 18, 1909:
“GEO. OTIS SMITH,
“_Director_.”
In the meantime, many of the explosives submitted, which heretofore had
been on the market as safety explosives, were found to be unsafe for
use in gaseous or dusty mines, and the manufacturers were permitted
to withdraw them. Their weaknesses being known, as a result of these
tests, the manufacturers were enabled to produce similar, but safer,
explosives. Consequently, applications for further tests continued
to pour in, as they still do, and on October 1st, 1909, a second list
of permissible explosives was issued, as follows:
“EXPLOSIVES CIRCULAR NO. 2.
“DEPARTMENT OF THE INTERIOR.
“United States Geological Survey.
“October 1, 1909.
“LIST OF PERMISSIBLE EXPLOSIVES.
“Tested prior to October 1, 1909.
“The following list of permissible explosives tested by the United
States Geological Survey at Pittsburg, Pa., is hereby published for
the benefit of operators, mine owners, mine inspectors, miners, and
others interested.
“The conditions and test requirements described in Explosives Circular
No. 1, issued under date of May 15, 1909, have been followed in all
subsequent tests.
“Subject to the provisions named below, a permissible explosive is
defined as an explosive which is in such condition that the chemical
and physical tests do not show any unfavorable results; which has
passed gas and dust gallery tests Nos. 1 and 3, as described in
circular No. 1; and of which, in test No. 4, 1½ pounds (680 grams) has
been fired into the mixture there described without causing ignition.
“_Permissible explosives tested prior to October 1, 1909._
“[Those reported in Explosives Circular No. 1 are marked *.]
------------------------------+-------------------------------------
Brand. | Manufacturer.
------------------------------+-------------------------------------
*Ætna coal powder A | Ætna Powder Co., Chicago, Ill.
Ætna coal powder AA | Do.
*Ætna coal powder B | Do.
Ætna coal powder C | Do.
Bituminite No. 1 | Jefferson Powder Co., Birmingham,
| Ala.
Black Diamond No. 3 | Illinois Powder Manufacturing Co.,
| St. Louis, Mo.
Black Diamond No. 4 | Do.
*Carbonite No. 1 | E. I. Du Pont de Nemours Powder Co.,
| Wilmington, Del.
*Carbonite No. 2 | Do.
*Carbonite No. 3 | Do.
*Carbonite No. 1-L. F. | Do.
*Carbonite No. 2-L. F. | Do.
*Coalite No. 1 | Potts Powder Co., New York City.
*Coalite No. 2-D. | Do.
*Coal special No. 1 | Keystone Powder Co., Emporium, Pa.
*Coal special No. 2 | Do.
*Collier dynamite No. 2. | Sinnamahoning Powder Manufacturing
| Co., Emporium, Pa.
*Collier dynamite No. 4. | Do.
*Collier dynamite No. 5. | Do.
Giant A low-flame dynamite. | Giant Powder Co. (Con.), Giant, Cal.
Giant B low-flame dynamite. | Do.
Giant C low-flame dynamite. | Do.
*Masurite M. L. F. | Masurite Explosives Co., Sharon, Pa.
*Meteor dynamite. | E. I. Du Pont de Nemours Powder Co.,
| Wilmington, Del.
Mine-ite A. | Burton Powder Co., Pittsburg, Pa.
Mine-ite B. | Do.
*Monobel. | E. I. Du Pont de Nemours Powder Co.,
| Wilmington, Del.
Tunnelite No. 5. | G. R. McAbee Powder and Oil Co.,
| Pittsburg, Pa.
Tunnelite No. 6. | Do.
Tunnelite No. 7. | Do.
Tunnelite No. 8. | Do.
------------------------------+-------------------------------------
“_Provided:_
“1. That the explosive is in all respects similar to sample submitted
by the manufacturer for test.
“2. That No. 6 detonators, preferably No. 6 electric detonators
(double strength), are used of not less strength than 1 gram charge,
consisting by weight of 90 parts of mercury fulminate and 10 parts of
potassium chlorate (or its equivalent), except for the explosive
’Masurite M. L. F.,’ for which the detonator shall be of not less
strength than 1½ grams charge.
“3. That the explosive, if frozen, shall be thoroughly thawed in a
safe and suitable manner before use.
“4. That the amount used in practice does not exceed 1½ pounds (680
grams), properly tamped.
“The above partial list includes all the permissible explosives that
have passed these tests prior to October 1, 1909. The announcement of
the passing of like tests by other explosives will be made public
immediately after the completion of the tests.
“With a view to the wise use of these explosives it may be well in
this connection to point out again certain differences between the
permissible explosives as a class and the black powders now so
generally used in coal mining, as follows:
“(_a_) With equal quantities of each, the flame of the black powder is
more than three times as long and has a duration three thousand to
more than four thousand times that of one of the permissible
explosives; the rate of explosion also is slower.
“(_b_) The permissible explosives are one and one-fourth to one and
three-fourths times as strong and are said, if properly used, to do
twice the work of black powder in bringing down coal; hence only half
the quantity need be used.
“(_c_) With 1 pound of a permissible explosive or 2 pounds of black
powder, the quantity of noxious gases given off from a shot averages
approximately the same, the quantity from the black powder being less
than from some of the permissible explosives and slightly greater than
from others. The time elapsing after firing before the miner returns
to the working face or fires another shot should not be less for
permissible explosives than for black powder.
“The use of permissible explosives should be considered as
supplemental to and not as a substitute for other safety precautions
in mines where gas or inflammable coal dust is present under
conditions indicating danger. As stated above, they should be used
with strong detonators, and the charge used in practice should not
exceed 1½ pounds and in many cases need not exceed 1 pound.
“JOSEPH A. HOLMES,
“_Expert in Charge Technologic Branch._
“Approved, October 11, 1909.
“H. C. RIZER,
“_Acting Director._”
The second list contains 31 explosives which the Government is prepared
to brand as permissible, and therefore comparatively safe, for use in
gaseous and dusty mines. An equally large number of so-called safety
powders failed to pass these tests. Immediately on the passing of the
tests, as to the permissibility of any explosive, the facts are reported
to the manufacturer and to the various State mine inspectors. When
published, the permissible lists were issued to all explosives
manufacturers, all mine operators in the United States, and State
inspectors. The effect has been the enactment, by three of the largest
coal-producing States, of legislation or regulations prohibiting the use
of any but permissible explosives in gaseous or dusty mines, and other
States must soon follow. To prevent fraud, endeavor is being made to
restrict the use of the brand “Permissible Explosive, U.S. Testing
Station, Pittsburg, Pa.,” to only such boxes or packages as contain
listed permissible explosives.
As these tests clearly demonstrate, both in the records thereof and
visually to such as follow them, that certain explosives, especially
those which are slow-burning like black powder, or produce high
temperature in connection with comparative slow burning, will ignite
mixtures of gas and air, or mixtures of coal dust and air, and cause
explosions. The results point out clearly to all concerned, the danger
of using such explosives. The remedy is also made available by the
announcement of the names of a large number of explosives now on the
market at reasonable cost, which will not cause explosions under these
conditions. It is believed that when permissible explosives are
generally adopted in coal mines, this source of danger will have been
greatly minimized.
_Explosives Investigations._--Questions have arisen on the part of
miners or of mine operators as to the greater cost in using permissible
explosives due to their expense, which is slightly in excess of that of
other explosives; as to their greater shattering effect in breaking down
the coal, and in giving a smaller percentage of lump and a larger
percentage of slack; and as to the possible danger of breathing the
gases produced.
Observations made in mines by Mr. J. J. Rutledge, an experienced coal
miner and careful mining engineer connected with the Geological Survey,
as to the amount of coal obtained by the use of permissible and other
explosives, tend to indicate that the permissible explosives are not
more, but perhaps less expensive than others, in view of the fact that,
because of their greater relative power, a smaller quantity is required
to do the work than is the case, say, with black powder. On the other
hand, for safety and for certainty of detonation, stronger detonators
are recommended for use with permissible explosives, preferably electric
detonators. These may cost a few cents more per blast than the squib or
fuse, but there is no danger that they will ignite the gas, and the
difference in cost is, in some measure, offset by the greater certainty
of action and the fact that they produce a much more powerful explosion,
thus again permitting the use of still smaller quantities of the
explosive and, consequently, reducing the cost. These investigations are
still in progress.
Concerning the shattering of the coal: This is being remedied in some of
the permissible explosives by the introduction of dopes, moisture, or
other means of slowing down the disruptive effect, so as to produce the
heaving and breaking effect obtained with the slower-burning powders
instead of the shattering effect produced by dynamite. There is every
reason to believe that as the permissible explosives are perfected, and
as experience develops the proper methods of using them, this difficulty
will be overcome in large measure. This matter is also being
investigated by the Survey mining engineers and others, by the actual
use of such explosives in coal-mining operations.
Of the gases given off by explosives, those resulting from black powder
are accompanied by considerable odor and smoke, and, consequently, the
miners go back more slowly after the shots, allowing time for the gases
to be dissipated by the ventilation. With the permissible explosive, the
miner, seeing no smoke and observing little odor, is apt to be
incautious, and to think that he may run back immediately. As more is
learned of the use of these explosives, this source of danger, which is,
however, inconsiderable, will be diminished. Table 1 gives the
percentages of the gaseous products of combustions from equal weights of
black powder and two of the permissible explosives. Of the latter, one
represents the maximum amount of injurious gases, and the other the
minimum amount, between which limits the permissible explosives
approximately vary.
Such noxious gases as may be produced by the discharge of the explosive
are diluted by a much larger volume of air, and are practically
harmless, as proven by actual analysis of samples taken at the face
immediately after a discharge.