Introduction
In the first three lessons of this tutorial we examined the water
content, phase state, and particle/vapour partitioning of single salt
solutions, and mixtures containing both a salt and an acid. In the
next three lessons we will study the behaviour of a two salt mixture.
In this lesson we look at the water content at various relative humidities.
Preparation
Before starting, ensure that this browser window occupies only the
left half of your screen. You should leave enough
space for another browser window where you can
enter data into
E-AIM and read the results. If your screen is too small for
two windows, print out this tutorial and use this window to enter data and
read
E-AIM's results. In these lessons we assume that you will
have two browser windows open.
Select this
link to open a second browser window containing the data
input page for "simple" calculations using Model III
(http://www.aim.env.uea.ac.uk/aim/model3/model3a.php). Arrange
the windows on your screen so that both are visible and the left window
contains this text.
The Lesson
This consists of the two sets of calculations described in the links below,
which should be done in the order listed.
You have completed Lesson 4, and learned that:
- The water content of particles increases as more compounds are added,
and the total amount of soluble material increases.
- At relative humidities very close to 100% the water uptake of
an NH4NO3/NaNO3 mixture
is approximately equal to the water uptake of the same number of moles
of NH4NO3 alone. This relationship
breaks down at lower relative humidities where the solutions are more
concentrated.
- The Zdanovskii-Stokes-Robinson equation predicts the water uptake of
a mixed solution from the values for each of the individual solutes
at the same water activity as the mixture. This relationship works
well at low relative humidities.
Now proceed to Lesson 5, which examines how
solids form in mixed aqueous aerosols.