Colored flames

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Since the first plastic cellulosic was produced in 1868, there has been an evergrowing demand for specially compounded plastics. Using a post-reactor technique, plastics can be compounded by alloying or blending polymers in addition to using additives such as colorants, flame retardants, heat or light stabilizers, lubricants, fillers, and/or reinforcements (Fig. 6-6). With reinforcements the resulting reinforced compounds are usually referred to as reinforced plastics (RPs). 

Additives (antioxidants, antiozonants, softeners, tacfdfiers, peptisers, scorch inhibitors, colorants, flame retardants, blowing agents, process aids, etc.)... 

The element revealed itself through spectacular violet-colored flames and several red spectral lines. The metal melts at 38 °C, is very soft, and extremely reactive (burns in air and reacts violently with water). Rubidium is stored under mineral oil. It is suitable as a scavenger (oxygen capture) in vacuum tubes, where it is deposited on the glass as a mirror. It can also be found in photocells and phosphors for screens (for example, for air-traffic controllers. Not physiologically important. The radioactive rubidium-87 is useful for age determination in geochronology (half-life ca. 50 billion years). 

They produce distinctive colored flames when burned lithium = crimson sodium = yellow potassium = violet rubidium = purple cesium = blue and the color of francium s flame is not known. Many of francium s characteristics have not been determined owing to the fact that it is rare and all of its many radioactive isotopes have short half-lives. 

Hydraulic fluids usually exhibit a consistent response of smoke color, flame color, autoignition temperature, and a whitish residue. 

When barium chlorate burns with fuel components, the oxygen acts as an oxidizer, and the burning is accompanied by the light emission of a green-colored flame. 

The gaseous products, NO2 and NO, also act as oxidizers when fuel components are present. When strontium nitrate burns with fuel components, a red-colored flame is formed. 

Kosanke, K. L, and Kosanke, B.)., The Chemistry of Colored Flame, Pyrotechnic Chemistry, Journal of Pyrotechnics, Inc., Whitewater, CO (2004), Chapter 9. 

Because of its higher melting point and less-exothermic decomposition, potassium perchlorate produces mixtures that are less sensitive to heat, friction, and impact than those made withKClO] [2]. Potassium perchlorate can be used to produce colored flames (such as red when combined with strontium nitrate), noise (with aluminum, in "flash and sound" mixtures), and light (in photoflash mixtures with magnesium). 

Mixtures of ammonium perchlorate with fuels can produce high temperatures when ignited, and the hydrogen chloride (HCl) liberated during the reaction can aid in the production of colors. These two factors make ammonium perchlorate a good oxidizer for colored flame compositions (see Chapter 7). 

Ammonium perchlorate (NH ClO ) This is a good oxidizer, and can be used to make excellent propellants and colored flames. However, it is a self-contained oxidizer-fuel system (much like ammonium nitrate). The mixing of NH f (fuel) and ClOa (oxidizer) occurs at the ionic level. The potential for an explosion cannot be ignored. Conclusion if this material is used, it must be treated with respect and minimum quantities of bulk powder should be prepared. 

The numerous requirements for a good oxidizer were discussed in detail in Chapter 3. An oxidizer for a colored flame composition must meet all of those requirements, and in addition must either emit the proper wavelength light to yield the desired color or not emit any light that interferes with the color produced by other components. 

To use potassium nitrate in colored flame mixtures, it is necessary to include magnesium as a fuel to raise the flame temperature. A source of chlorine is also needed for formation of volatile BaCl (green), or SrCl (red) emitters. The presence of chlorine in the flame also aids by hindering the formation of magnesium oxide and strontium or barium oxide, all of which will hurt the color quality. Shidlovskiy suggests a minimum of 15% chlorine donor in a color composition when magnesinm metal is nsed as a fuel [5]. 

Applications involving colored flame compositions will reqnire either a long-burning composition or a mixture that bums rapidly to give a burst of color. 

K. L. Kosanke, "The Physics, Chemistry and Perception of Colored Flames," Pyrotechnica VII, Pyrotechnica Publications, Austin, Texas, 1981. 

Photoflash" mixtures, 145-148 Photon, energy of, 46 Potassium chlorate acid with, 57 discovery of, 4 hazards of, 59, 109, 134 in colored flame mixtures, 156, 161... 

With good fuels (charcoal or active metals), potassium nitrate will burn well. Its use in colored flame compositions is limited, primarily due to low reaction temperatures. Magnesium may be added to these mixtures to raise the temperature (and hence the light intensity), but the color value is diminished by "black body" emission from solid MgO. 

Potassium chlorate was used in the first successful colored-flame compositions in the mid-1800 s and it remains in wide use today in colored smoke, firecrackers, toy pistol caps, matches, and color-producing fireworks. 

The production of a vividly-colored flame is a much more challenging problem than creating white light. A delicate balance of factors is required to obtain a satisfactory effect... 

If a binder is required in a colored flame mixture, the minimum possible percentage should be used. Carbon-containing compounds may be oxidized to the atomic carbon level... 

B. E. Douda, "Theory of Colored Flame Production," RDTN No. 71, U.S. Naval Ammunition Depot, Crane, Indiana, 1964. 

Most explosive and pyrotechnic reactions produce significant quantities of smoke, and this visible phenomenon may or may not be desirable. Smoke can obscure colored flames, and therefore attempts are made to keep the production of smoke to a minimum in such mixtures. However, a variety of smoke-producing compositions are purposefully manufactured for use in daytime signalling and troop and equipment obscuration, as well as for amusement and entertainment purposes. 

Potassium, — The yellow-colored flame produced by sodium bisulphate, when observed through cobalt glass, should exhibit only a transient violet color. 

Colored flames are produced by strontium compounds (red) barium compounds (green copper carbonate, sulfate, and oxide (blue) sodium... 

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