42. Depth Charge Marker Mk 2 is for night use to indicate the point of depth charge bar-rages and to provide a reference point for further search and attack against submarines. It burns with a yellow flame approximately ten inches high for 45 to 55 minutes, and is visible at night from the deck at distances up to four miles, depending on atmospheric conditions. This marker is a sealed metal cylinder seven inches high and five inces in dia-meter, having a centrally located tube which contains a charge of calcium phosphide, and is surrounded by a charge of calcium carbide. Pull ring tear strips on either end of the metal container to uncover two holes, which allow water to enter the cylinder and li-berate gases from the two chemicals. The calcium phosphide releases phosphine, a spontaneously ignited gas, which ignites acetylene, released by the action of water on the calcium carbide. See Fig. 11.

Figure 11. – Depth Charge Marker Mk 2 (For Night Use)

Operation

43. Depth Charge Marker Mk 2 is launched by hand at night several seconds after a depth charge has been dropped. The time lag is in order that the "boil" from the depth charge will not interfere with the burning of the marker. To launch the marker, rip the two tear strips from both ends and cast it overboard. The signal flame should appear on the surface in approximately 45 to 50 seconds.

Packing

44. Depth Charge Marker (Night) Mk 2 are now packed in pasteboard cases containing ten markers, each wrapped in corrugated paper. They were formerly shipped in cases containing 12 each. Pertinent information will be found stenciled on each marker.

Stowage

45. General pyrotechnic stowage rules outlined in paragraphs 9 to 12, inclusive, apply for Depth Charge Marker Mk 2, with one exception. This item must not be stowed in lockers or magazones equipped with sprinklers. This is because ignition is effected by chemical reaction between the ingredients and water.

Safety Precautions

46. In firing Depth Charge Marker Mk 2, the following safety measures must be taken:

(a) Do not remove the pull ring tear strips until ready to cast the marker overboard.

(b) Periodic inspection of stocks is recommended to insure that one or both tear strips have not been accidientally removed or partially opened.

(c) Markers with damaged tear strips should be disposed of at once.

(d) When removing markers from containers, do not handle or carry them by the tear strip rings.