Red flame compositions

The best flame emission in the red region of the visible spectrum is produced by molecular strontium monochloride, SrCl. This species, nnstable at room temperature, is generated in vapor phase in the pyrotechnic flame by a reaction between strontium and chlorine atoms. Strontium(II) chloride, SrCl2, would appear to be a logical precursor to SrCl, and it is readily available commercially, but it is much too hygroscopic to use in pyrotechnic mixtures. 

FIGURE 8.1 Emission spectrum of a red flare. Emission is concentrated in the 600 to 650 nm region. The primary emitting species are SrCl and SrOH molecules in the vapor state. 

To keep the SrCl from oxidizing in the flame, Shidlovskiy recommends using a composition containing a negative oxygen balance (excess fuel). Such a mixture will minimize the reaction 

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It is also astonishing how the rich blue of a cornflower (Centaurea cyanus) and the majestic red flame of the com poppy (Papaver rheas) each derive from the same chromophore - again based on an anthrocyanidin. The pH of cornflower and poppy sap does not vary with soil composition, which explains why we see neither red cornflowers nor blue com poppies. 

This material is rarely used as the only oxidizer in a composition, but is commonly combined with potassium perchlorate in red flame mixtures. It is a white crystalline solid with a melting point of approximately 570°C. It is somewhat hygroscopic, so moisture should be avoided when using this material. 

The diagram is quite convenient for designing colour flame compositions. For example, when a red colour represented by Pi is mixed with a green the new colour moves along the straight line P -Pilike P The coordinates have the following relations ... 

The composition is charged into a canister and closed with a lid which has an outlet hole. Uhen it is ignited, a small red flame jets out of the hole and produces black smoke from the top. The chemical reaction may take place as follows ... 

Strontium nitrate burns in combination with shellac in the ratio 10 2 producing a red flame, but it produces a large amount of solid ash When the composition is charged in a paper tube and burnt, the ash remains like a stick in the burning position and disturbs the flame to the point of... 

Tests should he performed to determine the effect of varying the gas composition on standard restricted-end deflagrations (RED) results. The present protocols do not require this, nor do they require varying the ignition location despite evidence that this affects flame arrester performance. 

Generally, flame retardants for engineering PET compositions are based on bromine-containing compounds (such as brominated polycarbonate, decabro-modiphenyl oxide, brominated acrylic, brominated polystyrene, etc.). Such compounds are available commercially (such as from the Ethyl Chemical Corporation, Great Lakes Chemical Corporation, Dead Sea Bromine Company, etc.) In addition, the flame-retardant package generally contains a synergist, typically sodium antimonate. PET may also be flame-retarded with diarylphosphonate, melamine cyanurate or red phosphorus. 

In practice, both red and green star compositions are formulated to have a negative oxygen balance i.e. there is an oxygen deficiency) since the presence of a reducing atmosphere in the flame inhibits the oxidation of MCI to MO (where M is Sr or Ba), thus enhancing the colour purity of the flame. 

Elemental composition K 40.23%, S 33.00%, C 12.36%, N 14.41%. Potassium can be measured in an aqueous solution by flame photometry, AA, or ICP/AES (see Potassium). Thiocyanate anion can be measured by Volhard titration against a standard solution of silver nitrate in the presence of ferric ammonium sulfate. The color of the solution turns red at the end point. 

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]. 

Many other dyestuffs may be used. Paranitraniline Yellow gives a canary yellow smoke, and Flaming Red B gives a crimson-colored smoke by comparison with which the smoke from Para-nitranilinc Red appears to be scarlet. None of the colored smoke compositions are adapted to indoor use. All the smokes are unpleasant and unwholesome. 

A similar kind of synergy was investigated by Cui et al.,90 who prepared by melt blending nano-modified ATH using oxalic acid, a red phosphorus masterbatch and high impact polystyrene (HIPS). Unfortunately, the use of variable amounts of HIPS in the compositions has limited the possibility to see evidence of synergistic effects. The authors have stressed the well-developed and robust character of the char layer formed after UL-94V flame test for the composition HIPS/modified ATH/ Red phosphorus (68/20/12). The use of FTIR confirmed also that both P-O-P and P-O-C groups were present in the char. 

F. Laoutid, L. Ferry, J.-M. Lopez Cuesta, and A. Crespy, Red phosphorus aluminium oxide compositions as flame retardant in recycled PET, Polym. Degrad. Stabil., 2003, 82 357-363. 

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