From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: rec.pyrotechnics
Subject: Re: Carbide
Date: 9 Mar 1997 06:30:27 GMT

In article <19970309001400.TAA14842@ladder01.news.aol.com>, kn03@aol.com
(KN03) says:

>pfrazier@netcom.ca wrote:
>
>>Sorry to sound dumb, but what is Carbide?
>
>It refers to calcium carbide, a compound which decomposes and forms
>acetylene gas, and calcium hydroxide, upon contact with water.  It was
>once widely used for lighting, hence the name "limelight".  It's fun to
>play with.

"Limelight" is the light emited by a piece (cylinder) of calcium 
oxide (quicklime) when it is heated to incandescent temperatures 
by a very hot flame such as that produced by a mixture of oxygen 
and hydrogen.

Jerry (Ico)

From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Newsgroups: sci.chem
Subject: Re: Lime Light
Date: Sat, 30 Jan 1999 18:42:36 GMT

"Ivan W Miller" <REITZ_PANTHER@prodigy.net> wrote:

>Does anyone know what reation was used in the old theater "lime
>lights"?

Essentially, it was a calcium oxide element heated to incandescence
by an almost invisible hydrogen-oxygen flame, although some lamps
used coal gas-oxygen flames.

The limelight was developed by Thomas Drummond between 1823-5 for
surveying, with detection distance of around 66 miles. That's why
it's also known as a "Drummond" or "calcium" light. In the early
days the hydrogen was produced from granulated zinc and sulfuric
acid, and the oxygen produced from heating manganese dioxide
( sometimes with potassium chlorate ). The gases were bubbled
through water into large fabric or leather bags that were squashed
to expell the gases into the flame. Don't try this at home without
carefully investigating the actual lamp design, as the high flame
speed of hydrogen-oxygen mixtures is likely to result in flashbacks.

The preparation and storage of the calcium oxide cylinders are
critical, as any reactions with moisture and CO2 in the air renders
the lime useless, and ordinary lumps of calcium oxide just shatter.
Originally, they were stored in hermetic tins, or dip-sealled in
paraffin wax. As the calcium oxide is eroded, the lamp adjustment
slowly moved the flame to a new part of the cylinder.

There is an excellent discussion of the limelight, along with
a detailed preparation procedure for making the lime cores ( from
more readily available calcium carbonate cores ) in
" A Reacquaintance with the Limelight "
  M.B.Hocking and M.L.Lambert
  J.Chem.Ed v.64 n.4 p.306-310 (1987)
The journal should be available at most educational institutions
with a chemistry department.

  Bruce Hamilton