Japanese partiality toward the tactical use of smoke, and various materiels
employed by the Japanese army's* "smoke" units have been discussed in Tactical
and Technical Trends No. 21, p. 11; No. 27, p. 12. Recent
reports on this materiel provides additional information in the form of descriptions of the
Japanese frangible smoke grenade and the Japanese Type "99" self-projecting
The Japanese frangible smoke grenade is an iron-capped, spherical glass
flask with a short neck and flat bottom. Measurements of the flask are:
|Overall height|| ||85 mm|
|Diameter (o.d.)||65 mm|
|Weight (empty)||161.2 grams|
|Thickness of wall||2 mm|
|Volume (to base of neck)||150 ml|
The closure consists of a red rubber stopper held under a red rubber washer within an
inner iron crown cap, this being enclosed by a heavier iron outer crown cap.
Filling: The liquid filling of the grenade has the following properties:
|Height of filling|| ||31 mm|
|Specific gravity (calculated)||1.69|
| Titanium tetrachloride||51.5%|
| Silicon tetrachloride||46.7%|
| Titanium and silicon oxides, by difference||1.8%|
The grenade is so shaped as to be easily thrown by hand. Titanium and silicon
tetrachlorides are readily hydrolyzed by the moisture if the air, with the
formation of the respective hydroxides and hydrochloric acid. The smoke produced
is formed from the fumes of hydrochloric acid and the particles of hydrated
titanium and silicon oxides.
The smoke grenade is intended for screening operations. Though both
titanium and silicon tetrachlorides are irritating to the skin as liquids, in ordinary
field concentrations the smoke is hardly irritating enough to the respiratory system
to cause coughing. Because of its size, the grenade used singly is ineffective for
a continuous screen, but is intended for use at short-range such as screening the
gun port of a pill-box or tank.
Comparison with Comparable U.S. Equipment
Titanium tetrachloride-silicon tetrachloride mixtures are not used by the
U.S. Titanium tetrachloride alone, designated FM, is classed as limited standard
for filling CWS smoke munitions but is not used as filling for frangible grenades.
The Japanese Type "99" self-projecting smoke candle has an outer
cylinder, 8 inches in length, olive drab in color. The weight of the candle
is 1283 grams (2.82 pounds) including a filling weighing 643 grams (1.41 pounds).
The starter mixture in a candle which has been examined was:
|Potassium Nitrate|| ||53.9%|
The smoke mixture in the candle examined analysed as follows:
|Hexachlorethane || ||46.5%|
Evidently this self-projecting candle can be used for setting up an advance
smoke screen in much the same manner as is accomplished by mortar or artillery
shells, except that the range is shorter. There is a delay train in front of the
starter mixture. This delays ignition of the candle for a definite time after it has
been propelled from the outer case. The delay time has not been determined.
There is no U.S. munition comparable to the Japanese Type "99" self-projecting
smoke candle. In tactical use it can be compared to the M-8 HC smoke
grenade for very short range and to the small HC filled rockets, mortar shells and
the 75-mm base ejection shell.
*To allay suspicion, all chemical units in the Japanese army are referred to as "smoke" units.