Chemical warfare

by Amos A. Fries; Clarence J. West

Apparatus for Smoke Production

Smoke Box

The smoke box was developed for the Navy for use when it was desirable to have the smoke screen generated away from the ship. (The smoke funnel, described later, was operated on board ship). The float consists of an iron container (holding the smoke mixture) surrounded by an iron float to support the apparatus when it is thrown into the water ([Fig. 91]). The iron container consists of a cylinder 22 inches high and 10 inches in diameter. One inch holes are bored 1½ inches from the top of this cylinder, from which the smoke is emitted. The iron float is about 2 feet in diameter and 8 inches deep. This box holds approximately 100 pounds of smoke mixture, and is so constructed that it will float one hour. When ignited, the mixture burns 9 to 9½ minutes. The smoke produced has a T. O. P. of about 1900. [Fig. 92] shows the Navy Smoke Box in action.

Fig. 91.—Navy Smoke Box.

Fig. 92.—Navy Smoke Box in Action.

Smoke Candle

Smoke candles are used for producing a cloud of smoke for screening purposes in or behind the lines. They are made by packing about three pounds of the modified Berger Mixture in a container ([Fig. 93]) (galvanized can 5¼ inches by 3½ inches) and are lighted by means of the match head type of ignition. Smoke is given off at a uniform rate for about 4 minutes, forming a dense, fog-like cloud which hangs low ([Fig. 94)]. This smoke is absolutely harmless, and can be breathed without discomfort. The obscuring power is high and, with a favorable wind, a small number of the candles will produce a screen sufficiently dense to allow operations to be carried out unseen by the enemy.

Fig. 93.—B. M. Smoke Candle.

Smoke Grenade

The smoke grenade is also designed for use in trench and field warfare, where it is desired to produce a dense smoke screen. It is made by packing 340 grams of the standard smoke mixture in an ordinary light metal gas grenade. Around the top of the grenade are vents closed by a zinc strip. The ignition is caused by the standard bouchon when the grenade is thrown. The heat of the reaction burns through the zinc strip and a dense cloud of smoke is evolved for 45 seconds.

Fig. 94.—Smoke Cloud from B. M. Candle.

Stannic chloride has also been used extensively in hand grenades, as it gives a very disagreeable cloud of smoke upon detonation. Due to the high prices and urgent need of tin for other purposes, silicon tetrachloride was substituted for tin tetrachloride towards the close of the war. A mixture of silicon tetrachloride and chloropicrin was also used. This not only gives a very good smoke cloud, but combines with it the toxic properties of the chloropicrin cloud.

The method of firing the smoke grenade is the same as that of any grenade using the same type of bouchon. Usually the grenade is grasped in the hand for throwing in such a manner that the handle of the bouchon is under the fingers. The safety clip is pulled out with the other hand and the grenade is thrown with an overhand motion. When the grenade leaves the hand, the handle of the bouchon flies off, allowing the trigger to hit the cap which ignites the fuse.

The white phosphorus combined hand and rifle grenade became the standard smoke grenade by the end of the war. Stannic chloride was used to clear out dugouts, but not as a smoke producer.

Stokes’ Smoke Shell

Fig. 95.—Stokes’ Smoke Shell.

The Stokes’ smoke shell was perfected to furnish a means of maintaining the best possible smoke screen at long ranges by means of an easily portable gun. The 3-inch Stokes shell, as adapted for combustion smokes, weighs about 13 pounds and contains about 4 pounds of standard smoke mixture. This shell is designed to produce a continuous screen over a period of 3 to 4 minutes.

Livens Smoke Drum

The Livens smoke drum was designed for use with the 8-inch Livens projector, so as to produce a smoke screen of large volume and long duration at long ranges. The drum, as adapted for combustion smokes, weighs 17.5 pounds empty and 49 pounds loaded. The smoke-gas mixture was specially adapted for use in the Livens drum.

Fig. 96.—Livens Smoke Bomb.

Smoke mixtures in Livens were never used to any considerable extent in the war and it is questionable if they ever will be. A Livens can usually only be fired once before resetting, hence Stokes mortars are used whenever possible.

Smoke Funnel

The smoke funnel was developed for the production of a white smoke cloud from the stern of a vessel. The smoke producing materials are liquid ammonia and silicon tetrachloride, with carbon dioxide as a compressing medium. This is the most satisfactory compressing medium, because: (1) The silicon tetrachloride is forced out at nearly constant pressure. (2) The carbon dioxide is easily compressed to a liquid and can be handled in this form. Further, it has a vapor pressure of 800 pounds at 60° F., and a cylinder can be nearly emptied without loss in efficiency. (3) Carbon dioxide is sufficiently soluble in silicon tetrachloride to cause the latter to effervesce and thus materially aid in its evaporation on spraying. (4) Liquid carbon dioxide, behaving in a manner similar to liquid ammonia, affords a means for the silicon tetrachloride to “keep pace” with the ammonia, under changes in temperature, and thus ensures a more nearly neutral, and therefore the most effective, smoke.

Fig. 97.—Navy Smoke Funnel.

The smoke funnel proper consists of an open end cylinder, about 2 feet in diameter and 7 feet long, mounted in a horizontal position on an angle iron frame. At one end is an 18-inch fan securely fastened to the cross supports. This fan is operated by hand, through gears giving a ratio of about 30 to 1. The silicon tetrachloride enters the cylinder through a pipe, which terminates in four spray nozzles, while the ammonia enters through a single nozzle. The air forced into the funnel serves to hydrolyze the silicon tetrachloride and mixes the vapors. The resulting reaction evolves a dense white cloud of very large volume and high obscuring power. One set of cylinders is capable of maintaining this cloud for over 30 minutes. Under normal conditions the discharge is at the rate of 2 pounds of silicon tetrachloride to 1 pound of ammonia. To stop the smoke, the silicon tetrachloride is closed first, the ammonia allowed to run about half a minute, and the fan is shut off last.

Fig. 98.—Navy Smoke Funnel in Operation.

Smoke Knapsack

The smoke knapsack furnishes a portable apparatus for smoke production. The gross weight is about 70 pounds; when in operation it gives a dense white smoke for about 15 minutes. The operation may be intermittent or continuous and the quantity of smoke is sufficient to completely hide one platoon of men in skirmish formation with a 5-mile per hour enfilade wind. The apparatus consists of two steel tanks about 26 inches in height and 6 inches in diameter. From the side of each tank, but near the bottom, extends a short pipe on which is placed a suitable valve. A flexible armored hose connects the valve to a short length of pipe which is equipped with spray nozzle. The cylinders are charged with silicon tetrachloride and ammonia under pressure. The valves may be operated with the left hand, while the sprayer apparatus is held in the right. The release buckles are within easy reach of both hands.

Shell

While many special devices have been developed by means of which the gas troops and infantry are able to set up smoke clouds on short notice, the smoke shell, fired by the artillery, always played an important part in this work. In the same way that a large number of the poison gases were adapted to artillery use, so were most of the smoke producing substances.

As a filler for smoke shell, phosphorus easily ranks first, and is approached only by sulfur trioxide in very humid weather. A rough approximation to the relative values of some of its rivals is given in the following table:

White phosphorus	100
Sulfur trioxide	60-75
Stannic chloride	40
Titanium chloride	25-35
Arsenic chloride	10

Comparison of the value of different forms of phosphorus for shell purposes has invariably pointed to the superiority of the white variety. Mixtures of white and red (2 to 1) have also proved effective.

A complete barrage over a front of 200 yards can be established in from 40 seconds to 1 minute and maintained by firing a salvo followed by battery fire of 3 seconds. Four 4.5-inch howitzers could maintain an effective barrage over a front of 1000 yards. The influence of sunshine is very marked, as in moist, cool weather one shell every 15 seconds is sufficient.

Fig. 99.—Smoke Screen for Tanks.