CONDITIONS UNDER WHICH EXPLOSIVES ARE TESTED.

The conditions under which the Bureau of Mines tests explosives to determine whether they shall be placed on its list of permissible explosives are as follows:

1. The manufacturer is to deliver to the BUREAU OF MINES, FORTIETH AND BUTLER STREETS, PITTSBURG, PA., three weeks prior to the date set for tests, 100 pounds of each explosive that he desires to have tested. He is to be responsible for the care, handling, and delivery of this material to the testing station and he is to have a representative present during the tests. In order to avoid duplication of work, it is requested that the smallest size of cartridge that the manufacturer intends to place on the market be sent for these tests.

2. No one is to be present at or participate in these tests except the necessary Government officers at the experiment 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 testing station by the date set, of which date due notice will be given by the Bureau of Mines.

4. A list of the explosives which pass certain requirements satisfactorily will be furnished to State mine inspectors and will be made public in such other manner as may be considered desirable.

5. The details of results of tests are to be considered confidential by the manufacturer and are not to be made public prior to official publication by the Bureau of Mines.

6. From time to time field samples of permissible explosives will be collected, and tests will be made of these explosives as they are supplied for use in coal mines in the various States.

TEST REQUIREMENTS FOR EXPLOSIVES.

The tests will be made by the engineers of the United States mining experiment 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 deflective power, as determined by the ballistic pendulum, to one-half pound (227 grams) of 40 per cent nitroglycerin dynamite in its original wrapper, of the following formula:

Each charge shall be fired with an electric detonator (exploder or cap) strong enough 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.

In order that the dust used in tests 2, 3, and 4 may be of the same quality, it is always taken from the same mine, ground to the same fineness, and used while still fresh.

The following are the tests to which are subjected the explosives that the Bureau of Mines is asked to place in the list of permissible explosives:

a

Test 1. Ten shots each with the charge as described above, in its original wrapper, shall be fired, each tamped with 1 pound of clay stemming, at a gallery temperature of 77° F., into a mixture of gas and air containing 8 per cent of gas (methane and ethane). An explosive is considered to have passed the test if no one of the ten successive shots ignites this mixture.

a

Test 2. Ten shots each with the charge as described above, in its original wrapper, shall be fired, each tamped with 1 pound of clay stemming, at a gallery temperature of 77° F., into a mixture of gas and air containing 4 per cent of gas (methane and ethane) and 20 pounds of bituminous coal dust, 18 pounds of which is to be placed on shelves along the sides of the first 20 feet of the gallery, and 2 pounds to be so placed that it will be stirred up by an air current in such manner that all or part of it will be suspended in the first division of the gallery. An explosive is considered to have passed the test if no one of the ten successive shots ignites this mixture.

a

Test 3. Ten shots each with the charge as described above, in its original wrapper, shall be fired, each tamped with 1 pound of clay stemming, 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 steel trestle placed in front of the cannon and 20 pounds placed on side shelves in sections 4, 5, and 6. An explosive is considered to have passed the test if no one of the ten successive shots ignites this mixture.

Test 4. A limit charge will be determined within 50 grams by firing charges in their original wrappers, without stemming, at a gallery temperature of 77° F., into a mixture of gas and air containing 4 per cent of gas (methane and ethane) and 20 pounds of bituminous coal dust, to be arranged in the same manner as in test 2. This limitcharge test is to be repeated five times under the same conditions before being established.

DEFINITION OF PERMISSIBLE EXPLOSIVE.

An explosive is called a permissible explosive when it is similar in all respects to the sample that passed certain tests by the national Bureau of Mines, and when it is used in accordance with the conditions prescribed by that bureau.

a Two pounds of clay stemming are used with slow-burning explosives.

The tests now prescribed as those a permissible explosive must have passed are those given above. But even the explosives that have passed those tests and are published as permissible explosives are to be considered as permissible explosives only when used under the following conditions:

1. That the explosive is in all respects similar to the 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 their equivalents), except for the explosives "Bental coal powder No. 2," "Detonite special," "Hecla No. 2," "Kanite A," "Masurite M. L. F.," "Titanite No. 7-P," and "Titanite No. 8-P," for which the detonator shall be of not less strength than the No. 7 (1 grams charge of the same mixture).

3. That the explosive, if frozen, shall be thoroughly thawed in a safe and suitable manner before use.

4. That the quantity used for a shot does not exceed 14 pounds (680 grams), properly tamped.

It must not be supposed that an explosive that has once passed the above-mentioned tests and has been published in lists of permissible explosives is thereafter to be considered a permissible explosive, regardless of its condition or the way in which it is used. Thus, for example, an explosive named in the permissible list, if kept in a moist place until it undergoes a change in character, is no longer to be considered a permissible explosive. If used in a frozen or half-frozen condition, it is not when so used a permissible explosive. If used in excess of the quantity specified (1) pounds), it is not when so used a permissible explosive. And when the other conditions have been met, it is not a permissible explosive if fired with a detonator of less than the prescribed strength.

Moreover, even when all the prescribed conditions have been met no permissible explosive should necessarily be considered as permanently being a permissible explosive, but any permissible explosive when used under the prescribed conditions may properly continue to be considered a permissible explosive until notice of its withdrawal or removal from the list has been officially published, or until its name is omitted from a later list published by the Bureau of Mines.

Furthermore, the manufacturers of a permissible explosive may withdraw it at any time when introducing a new explosive of superior qualities. And after further experiments and conferences, the Bureau of Mines may find it advisable to adopt additional and more severe tests to which all permissible explosives may be subjected, in the hope that the lives of miners may be safeguarded better through the use of only those explosives that may pass the more

severe tests.

Subject to the conditions and provisions stated above, the following explosives are classed as permissible explosives:

Permissible explosives tested prior to January 1, 1911.

[Those reported in previous circulars are marked with an asterisk (*).]

The above list includes all the permissible explosives that have passed the required tests prior to January 1, 1911. The announcement of the passing of like tests by other explosives will be made public after the completion of the tests.

Recent tests by the Bureau of Mines indicate that some of the explosives on this list should not be used in coal mines for "adobe shots," a in breaking large pieces of rock or coal or in breaking down stoppings, where either gas or dry inflammable dust is present in quantities or under conditions that indicate danger. It is expected that a new test will be added to the present test requirements that will determine what explosives should be permissible when used for such shots. In this event a few of the explosives now on the list may be eliminated, and all new explosives submitted for test may be subjected to the new requirement.

CLASSES OF PERMISSIBLE EXPLOSIVES.

In order that the users of explosives may know the characteristic component of each of the permissible explosives on this list, and that this knowledge may assist them in selecting explosives according to their needs, the explosives on this list are arranged in four classes, as follows:

1. Ammonium nitrate powders, represented by Aetna coal powder AA, Bental coal powder No. 2, Bituminite No. 5, Bituminite No. 7, Coalite No. 3-X, Coal special No. 4, Collier powder No. 5, Collier powder No. 3, Collier powder No. 5 special, Collier powder No. 5-L. F., Collier powder No. X, Detonite special, Hecla No. 2, Kanite A, Masurite M. L. F., Monobel No. 1, Monobel No. 2, Monobel No. 3, Titanite No. 3-P, Titanite No. 7-P, and Titanite No. 8-P.

2. Hydrated powders, represented by Meteor AXXO, and Giant low-flame dynamite A, B, and C.

3. Nitrostarch powders, represented by Trojan coal powders A, B, C, D, E, and F.

4. Nitroglycerine powders, represented by all the others on the list. With the exception of Detonite special, Hecla No. 2, Kanite A, Masurite M. L. F., Titanite No. 3-P, Titanite No. 7-P, Titanite No. 8-P, and the Trojan coal powders A, B, C, D, E, and F, all of the powders mentioned in the list contain nitroglycerin, and they are all of the general nature of dynamite; but the components and proportions of the dopes have been so chosen and the mixtures so made as to modify greatly the shattering effect upon explosion and to yield a relatively cool flame.

The explosives on the list which are marked L. F. contain nitrosubstitution compounds or other materials which have been added

a For an "adobe shot" the explosive is placed on the thing to be broken and covered with clay. This method of using an explosive is also called “ "bulldozing."