Newsgroups: sci.chem
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Boiling stones
Date: Tue, 25 Feb 1997 15:29:50 GMT

cjb@red.seas.upenn.edu (Chris Brinkerhoff) wrote:

>What are boiling stones made of?

In my days in industry, they were made from broken
cups and saucers from the cafetaria. These days, the
ones from chemical supply houses are made from fused
alumina. Many chemists in a hurry forget to add the 
few chips, and see the spheres skating rapidly across the
superheated liquid surface, and drop just one chip
down the condenser or thermometer hole in the vain hope 
that no geyser will appear. 

Another very common error is to forget to add fresh chips
whenever the solution has cooled and is to be reheated,
especially when distilling larger volumes of solvent.
The chip surfaces get covered with residues, and are
ineffective, so a few chips need to be added each time.   

    Bruce Hamilton

From: "\"Uncle Al\" Schwartz" <UncleAl0@ix.netcom.com>
Newsgroups: sci.chem
Subject: Re: Boiling stones
Date: Mon, 24 Feb 1997 18:05:00 -0800

Chris Brinkerhoff wrote:
> 
> What are boiling stones made of?
> I was just wondering, thanks.
> Chris

The best boiling stones are 1/8" to 1/4" carborundum abrasive grit -
cheap, inert, and loaded with nucleation sites.  There are fluorocarbon
stones, calcium sulfate stones, and other stuff.  The question is, will
they stay crunchy even in milk?

-- 
Alan "Uncle Al" Schwartz
UncleAl0@ix.netcom.com ("zero" before @)
http://www.ultra.net.au/~wisby/uncleal.htm
 (Toxic URL! Unsafe for children, Democrats, and most mammals)
"Quis custodiet ipsos custodes?"  The Net!