Colored Signal Smokes A Demonstration WILLIAM F. KIEFFER and JULIA M. RESKO Western Reserve University, Cleveland, Ohio
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HE use of colored smokes represents an important . . . mnovation in slgnallng techniques during the present war. .Research carried out a t the time of the last war indicated the desirability of using volatilized dyes in preference to finely dispersed inorganic solids. They. were not widely employed a t that time, however, due to the high cost of the dyes as produced by the then infant American dye industry. Dye smokes can be produced in abundant clouds with colors whose vividness makes identification simple. Reports by the Chemical Warfare Service are available and give formulas of useful dyes as well as mixtures whose ignition produces the smoke.'. The essential constituents of a smoke-producing mixture are: (a) a combustible material, (b) an oxidizing agent, (G) an easily sublimed dye, and (d) a cooling agent. The smoke itself consists of minute aggregates of the dye molecules which have been dispersed into the air. This dispersion is accomplished by the heat generated from the oxidation initiated when the mixture is ignited. The oxidizing agent is usually the freshman's old friend, potassium chlorate. Sucrose or sulfur is most frequently included as a combustible substance. A bright colored dye, in order to be used successfully, must either be readily sublimed or be one whose boiling and melting points are close together. In addition, the dye molecule must be relatively stable against decomposition or transformation by heating. The anthra' quinone dyes have been found generally acceptable by these criteria. During the smoke generation the rate of the oxidation must be tempered by the inhibitory effect of a cooling agent. This serves to absorb some of the heat so that the temperature of the combustion does not advance beyond the kindling temperature for the organic dyestuff. The alkali bicarbonates and certain ammonium compounds are satisfactorily used as cooling agents. The production of colored smokes as a classroom demonstration in the elementary course serves as an interesting illustration of potassium chlorate's usefulness. Too often the student dismisses it merely as the substance capable of yielding its oxygen when heated in company with manganese dioxide. Occasionally the freshman acquires the other extreme of personal experience with its dangerous aspects by either knowingly or unknowingly dropping some concentrated sulfuric acid on it. The experiments here described demon-
YELLOW SMOKE
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Auramine 0 . . . . . . . . . . . . . . . . . . . . . . ..50 Per cent Kc101. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Percent Sulfur... . . . . . . . . . . . . . . . . . . . . . . . . . . ..10 Per cent . NaHC0 . . . . . . . . . . . . . . . . . . . . . . . . . .28Percent (NHd2CO4... . . . . . . . . . . . . . . . . . . . . . . 6 Per cent 2 8-Naphthaleneazodimethylaniline..... .64 Per cent KC10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Percent Sucrose.. . . . . . . . . . . . . . . . . . . . . . . . . . ..20 Per cent . . . . . . . . . . . . . . . . . . . . . . . 8 Per cent (NH4)2C04.. RED SMOKE
1 9-Diethylaminorosindone............ .62 Per cent KC10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Percent Sunose ............................. 26Percent . . . . . . . . . . . . . . . . . . . . . . . 6 Per cent (NHc)nGOa.. 2 1-Methylaminoanthraquinone........ .56 Per cent KCIO . . . . . . . . . . . . . . . . . . . . . . .:..... 7Percent Sulfur.. ........................... .10 Per cent NaHCOJ . . . . . . . . . . . . . . . . . . . . . . . . . . .20Percent (NHJ~GO,......................... 7 Percent ORANGE SMOKE
1 rr-Aminoanthraquinane... . . . . . . . . . . . .34 Per cent Auramine 0 . . . . . . . . . . . . . . . . . . . . . . ..20 Per cent KC10> . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Percent Sulfur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lopercent . NaHCOs. . . . . . . . . . . . . . . . . . . . . . . . .- 2 4 Per cent (NH,)2C904.. . . . . . . . . . . . . . . . . . . . . . . . 6 Per cent 2 I-Amino-8-Chloroanthraquinone..... .48 Per cent Auramine 0 . . . . . . . . . . . . . . . . . . . . . . . . 8 Per cent KCIO ............................. 6Percent Sulfur............................. 8Percent . NaHCO. . . . . . . . . . . . . . . . . . . . . . . . . . . 24Percent (NH,).C206... . . . . . . . . . . . . . . . . . . . . . . 6 Per cent VIOLET SMOKE
I-Methylaminoanthraquinone.. . . . . . .22 Per cent 1.4-Diamino-2.3-dihydroanthraquinone36 Per cent KC10I . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Percent Sulfur. . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 2 Per cent NaHCOa . . . . . . . . . . . . . . . . . . . . . . . . . . .14Percent (NH&CzO,......................... 8Percent GREEN SMOKE
Auramine 0 . . . . . . . . . . . . . . . . . . . . . . .-16 Per cent 1.4-Di-9-toluidinoanthraquinone.. .... .38 Per cent Sllfur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Percent 'NaHCOs. . . . . . . . . . . . . . . . . . . . . . . . . . .24Percent (NH.)GO,. . . . . . . . . . . . . . . . . . . . . . . . . 6 Per cent
strate its much safer yet equally spectacular and signi1. R a.. r.. w..m R . . "Production of colored smoke sianals." ficant utilization as an oxidizing agent. ...r.,v .A... Ifid. Eng. Chem., 18, i0 (1926). It was found that when small-scale mixtures were 2 TECHNICAL COMMAND OP THE CHEMICAL WARPARE SERVICE, made according to the data of the Chemical Warfare "Colored signal smokes." Ckm. Eng. N m s , 22, 1990 (1944).
Service2 they did not give consistently satisfactory be successfully used to slow the reaction, but its volaresults when ignited by heating. The method of initia- tility as a white smoke obscured the dye colors sometion tried was simply to heat the mixture in a porcelain what. The accompanying table lists satisfactory mixdish by means of a Bunsen burner. In every case the tures for five- to ten-gram samples. With small demonstration samples, the smooth evolution of the dye smoke was soon intermpted by violent sputtering which continued until the dye was evolution of smoke depends upon the constituents' benearly consumed, after which a few puffs of unpre- ing very finely pulverized and then thoroughly mixed. dictably colored smoke were given off. Various modi- The usual precaution against grinding potassium fications of the published formulas were tried as well as chlorate with combustible material should be emdifferent means of starting the oxidation. Satisfactory phasized if the preparation of these mixtures is assigned results for simple heat initiation were obtained by as a student project. Acknowledgment is made to the National Aniline lowering the amount of potassium chlorate, add'mg ammonium oxalate as a heat absorber, and increasing Division of Allied Chemical and Dye Corporation who the proportion of the dye. Ammonium chloride could supplied samples of dyes employed.
