Igniting cherry

A useful time-saving device in igniting aluminothermic charges is the so called ignition-cherry which is readily prepared as follows ... 

Heat the end of an iron bar, 15mm in diameter, for a length of 10cm to a cherry red heat (about 900°) and plunge it into a small quantity of explosive placed on a sheet of asbestos. If the explosive does not ignite or is difficult to ignite, and burns slowly without explosion,... 

When the vapors cease to bum and no Anther blue smoke can be observed, readjust the burner and hold the heat as at the beginning so as to make the bottom and lower part of the sheet-iron cmcible a cherry red, and maintain for exactly 7 min. The total period of heating shall be 30 2 min, which constitutes an additional limitation on the tolerances for the pre-ignition and burning periods. There should be no difficulty in carrying out the test exactly as directed with the gas burner of the type named, using city gas (20 to 40 MJ/m ), with the top of the burner about SO mm below the bottom of the cracible. The time periods shall be observed with whatever burner and gas is us. ... 

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