Re: Lead dioxide smoke

To my knowledge these smokes were patented in the 1930s. Ellern lists 3
compositions under "Inorganic Colored Smokes." Yellow is made with 66 potassium
dichromate, 20 bismuth tetroxide, and 14 magnesium powder. Orange is 35
potassium dichromate, 50 lead dioxide, and 15 magnesium. Brown is 35 lead
dioxide, 50 cupric oxide, and 15 magnesium powder. According to Ellern's
footnote 328, these are covered under US Pats. Nos. 1,920,254 (1933); 1,975,099
(1934); 1,975,785 (1934); and 2,091,977 (1937).

I have not seen any published or manuscript formulae for compositions of this
type earlier than these patents. If you have a "late 19th-century" citation, I'd
be very curious to know what it is. It wouldn't be the first time someone
patented an idea that in fact had long history in prior art (cf. Ralph Degn's
patent on titanium whistles!).

Ellern describes these compositions as yielding "smoke puffs." Lead dioxide is a
vigorous oxidizer, and in my experience (using fine magnesium powder) the orange
smoke when confined in a report case makes a respectable bang accompanied by a
flash and a nice puff of smoke which is, I suspect, finely divided red lead, the
product of an incomplete reduction of the lead dioxide. I'd sooner call it an
"orange smoke report." Such a composition could be used with nice effect in
Maltese-style daytime shells of timed rings of small reports.

I have not tried the other two compositions, but expect they would be similar in
their performance. They all function by a sort of Goldschmidt reaction; the
yellow smoke given by the yellow composition would largely be bismuth trioxide,
from incomplete reduction of the tetroxide; while the brown would be produced by
a mixture of red lead (as in the orange smoke) and elemental copper from the
reduction of cupric oxide. Note the similarity of the brown smoke to 'dragon's
egg' compositions.




In article <1146236049.896362.216600@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, John Reilly
says...

Anyone have experience with lead dioxide smokes? Evidently it was used
in the late 19th century as a military signal smoke (yellow brown);
probably similar to realgar smokes but easier to get.

John



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