it is safer to handle, but cannot be used so easily as an incendiary. Aerosol of burning phosphorus particles is an effective obscurant against thermal imaging systems. However, this effect is short-lived. After the phosphorus particles fully burn, the smoke reverts from emission to absorption. While very effective in the visible spectrum, cool phosphorus smoke has only low absorption and scattering in infrared wavelengths. Additives in the smoke that involve this part of the spectrum may be visible to thermal imagers or IR viewers. Dyes Various signalling purposes require the use of colored smoke. The smoke created is a fine mist of dye particles, generated by burning a mixture of one or more dyes with a low-temperature pyrotechnic composition, usually based on potassium chlorate and lactose (also known as milk sugar). Colored smoke screen is also possible by adding a colored dye into the fog oil mixture. Typical white smoke screen uses titanium dioxide (or other white pigment), but other colors are possible by replacing titanium dioxide with another pigment. When the hot fog oil condenses on contact with air, the pigment particles are suspended along with the oil vapor. Early smoke screen experiments attempted the use of colored pigment, but found that titanium dioxide was the most light scattering particle known and therefore best for use in obscuring troops and naval vessels. Colored smoke became primarily used for signaling rather than obscuring. In today's military, smoke grenades are found to be non-cancer causing, unlike the 1950s AN-M8 model. Sulfonic acid The smoke generator on the Medium Mark B tank used sulfonic acid. Tactics History The first recorded instance of the tactical use of a smoke screen has been at the Battle of Macau by the Dutch. A barrel of damp gunpowder was fired into the wind so that the Dutch could land under the cover of smoke. Land warfare Smoke screens are usually used by infantry to conceal their movement in areas of enemy fire. They can also be used by armoured fighting vehicles, such as tanks, to conceal a withdrawal. They have regularly been used since earliest times to disorient or drive off attackers. A toxic variant of the smokescreen was used and devised by Frank Arthur Brock who used it during the Zeebrugge Raid on 23 April 1918, the British Royal Navy's attempt to neutralize the key Belgian port of Bruges-Zeebrugge. For the crossing of the Dnieper