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Re: Ice cream sodas



Another possible effect is the difference in solubility in water of carbon
dioxide and ice cream. An even more dramatic effect occurs when table salt
is added to soda. Though nucleation may also contribute to the resulting
fizz, I theorize that NaCl "displaces" the CO2 in solution because NaCl is
much more soluble in water than CO2. The CO2 then has nowhere to go but
up. Does anybody know the solubility constants of NaCl and CO2 off the top
of their head?

A possible experiment: 1) Add fine, washed sand to soda. Since sand does
not dissolve in water, effect is entirely nucleation. 2) Add a strong,
saline solution to soda. Since salt is already in solution, there are no
nucleation sites.

Glenn
============
Glenn A. Carlson, P.E.
Xannah ASE
St. Peters, MO
gcarlson@xannah.com
====================

Date: Mon, 5 Mar 2001 16:52:40 -0700
From: PETER CRAFT <CRAFTYPHANTOM@FREEMAIL.COM.AU>
Subject: Ice cream sodas

Forgive my ignorance, but the day some chemistry students were making ice
cream sodas (dropping ice cream into some cola) and noted that when the
ice cream hits the soft drink it rapidly "fizzes" up. They were curious
about the cause of this sudden gas evolution as the same thing did not
occur when blocks of ice were dropped into a drink. This, they reasoned,
excludes temperature as being the only mechanism involved when the ice
cream was added. After consulting my fellow teachers the best we could
summize was that the rapidly melting ice cream my provide sites of
nucleation. We were uncertain about this as we are more familiar with
nucleation as an explanation in the process of boiling. Could anyone set
us right?