Charley, while it may be true that the presence of arsenic in a chlorate
composition leads to the liberation of free chlorine in burning, I've never
seen a reference to this in the literature.
On the other hand, Bernie Douda indicates in RDTN No. 71 ("Theory of Colored
Flame Production," NAD-Crane, 1964) that copper acetate survives at flame
temperature and emits in the blue range. (NOTE: In posts several days later it is added that "Acetate is mentioned
on page 14 of the PDF, 26 of the original, in connection w/ sodium-strontium-barium."--Mr. Emous, Anon.) It is possible that copper acetate
is one of the intermediate products of the decomposition of Paris green
(copper acetoarsenite) and that it accounts for the relative success of blue
compositions containing Paris green and potassium chlorate, but no chlorine
donor. Further support for this hypothesis is provided by the inferior
performance of Scheele's green (copper arsenite) when compared to that of
Paris green, as noted by several authorities.
Pyrotechnic color production was extensively investigated in the middle
nineteenth century. I doubt that Chertier, Tessier, and Websky - one or
another of them - failed to investigate just about any composition that had
promise and could be made with materials available to them. It is noteworthy
that some of the earliest blue compositions of the chlorate era utilized
copper acetate. It is sometimes unclear whether the neutral or the basic
acetate was meant by the trivial descriptions "verdigris" or "Grünspan."
However, the problem either salt poses for the pyrotechnist is the presence
of water of hydration. Note the similarities of their structures, and the
way the arsenite radical effectively substitutes for the water of hydration:
Basic copper acetate (blue verdigris): Cu(C2H3O2)2.CuO.6H2O
Cupric acetate (neutral verdigris): Cu(C2H3O2)2.H2O
Paris green: Cu(C2H3O2)2.3Cu(AsO2)2
Quoted post by Mike Swisher from PML archive
Posted Mon Feb 2 14:10:36 EST 2009
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