Transactions of the American Society of Civil Engineers, vol. LXX, Dec. 1910 | Page 6

be termed permissible explosives.
"Permissible explosives tested prior to May 15, 1909.
----------------------------+---------------------------------------- Brand. | Manufacturer. ----------------------------+---------------------------------------- ?tna coal powder A | ?tna Powder Co., Chicago, Ill. ?tna 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 1? 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 1? 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 1? 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 1? 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