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Science and Technology of Energetic Materials

Vol.73, No.5 (2012)

Research paper

Thermal properties of chemicals in fireworks measured with microcalorimetry
Ikumi Matsui and Shuji Hatanaka
p.142-146

Abstract

The blinker firework star called “kirakira-boshi” is composed of metals and antimony trisulfide (Sb2S3). In the manufacturing process, water is mixed with the composition. Using Mg and/or Magnesium-Aluminum alloy (MgAl) as the metal component can be a problem since their reactions are exothermic. We first analyzed distilled water and the water samples used in the manufacturing process using HPLC, and then we analyzed the water samples dispersed with Sb2S3. The results show that each water sample contains different anion groups.
We also performed microcalorimetric studies on the Mg-H2O and Mg-Sb2S3-H2O systems using the C-80 calorimeter of membrane mixing vessel at different temperature levels. An immediate exothermic reaction was observed when water was dropped on the Mg-H2O system, but stopped soon after because the reaction was limited to the surface of the powder. On the other hand, when water was dropped on the Mg-Sb2S3-H2O system, the reaction continued for a long time, producing Mg (OH)2 and H2S.
Potassium dichromate (K2Cr2O7) is usually used to inhibit the reaction of a pyrotechnic containing Mg and water. In the case of the Mg-Sb2S3-H2O system at 35℃, K2Cr2O7 did not inhibit the reaction. An exothermic reaction was observed after a 6-hour induction period, which can be dangerous in an uncontrolled situation.

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Keywords

fireworks, magnesium (Mg), antimony trisulfide (Sb2S3), potassium dichromate (K2Cr2O7), microcalorimetry, blinker stars, exothermic reactions

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