### E-AIM Tutorial

 Lesson 6: Gas/aerosol Partitioning in Mixed Salt Aerosols

### Introduction

In Lesson 5, we examined solid/aqueous phase equilibrium in solutions containing two salts. Here we study the gas phase partitioning in a system containing the ions Na+, NH4+, H+, and NO3.

### 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 run the E-AIM model. 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 "comprehensive" calculations using Model III (http://www.aim.env.uea.ac.uk/aim/model3/model3b.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 three sets of calculations described in the links below, which should be done in the order listed.

### Conclusion

You have completed Lesson 6, and learned that:
• Non-volatile compounds such as sodium nitrate force the existence of a particulate phase under all conditions. This may be liquid or solid according to the relative humidity.
• The particle phase may be solid or aqueous or a mixture of the two depending on the chemical composition of the system, and whether volatile compounds (here HNO3 and NH3) are allowed to partition into the gas phase.
• Where there is equilibration between gas, liquid, and solid phases the behaviour of the system can be complex even at a fixed relative humidity. In part (c) of the lesson the equilibrium particulate phase ranged through solid, solid + liquid, liquid only, and to no particulate phase just by substituting the cation NH4+ for Na+.

Now proceed to Lesson 7, which examines how the properties of single electrolyte solutions depend upon temperature.