Your example shows that you are not familiar with atmopheric aerosols.

ammonium chloride is a minor substance and is not internally mixed with the much larger sodium chloride. So what do you really want to know?

THEN: go to the on-line ISORROPIA-model to directly calculate what you ask! here. Next time: do your homework first before you ask questions

Yes, Sir I am new to this field. Sorry for bothering with this bad example. I put the question in a wrong way...I actually asked about MIXED LABORATORY GENERATED aerosols.

I try EXPERIMENTAL or analytical environmental chemistry and am not familiar with the mathematical models. It would take time for me to understand the nuances, because they are not too simple I guess. But, I suppose it's to our advantage that we can interact with experts like you to understand the subject, even if it is through making immature questions.

I am trying to determine DRH & ERH values EXPERIMENTALLY for varying mixing ratios of strong electrolytes (mixed laboratory generated aerosols). There is a eutonic point (MDRH), independent of mixing ratio and a second DRH when the particle completely dissolves depending on the mole fraction of salts. The Deliquescence is two step and follows equilibrium thermodynamics.

However, is it possible that the during dehydration the efflorescence is single step and no Mutual ERH is observed? Hence, the expected core-shell morphology may also not be observed? Can the kinetic process of efflorescence make this deviation from thermodynamic predictions occur and can the lowest ERH be observed for a mixing ratio other than the eutonic if there is a common cation in the mixture. You can forget about the NH4Cl-NaCl example here.

However, I will try ISSOROPIA on-line as you suggested.

I also refer you to the extensive work of prof Scot T. Martin at Harvard, doing just what you are after. We also experimented with mixtures of the most abundant mixture of components, that is, ammonium nitrate / sulphate

Thank you Sir,

I have been reading Prof. Martin's review in Chem Reviews (2000). It will take me some time to understand all of your work. Your on-line guidance and small hints will be encouragement enough for me to go on trying. Since, so much has already been covered I have a long way to go.

Good luck and nice of you to respond so politely

I think AIM2 is useful for this purpose and it's very instructive and flexible. We used it recently to assign the difference between gravimetric and ion measurements to liquid water associated with sulfuric acid at the laboratory equilibration (35% RH) conditions.

Clegg, S.L.; Wexler, A.S. (2012). Extended AIM Aerosol Thermodynamics Model. prepared by University of East Anglia, Norwich, UK, http://www.aim.env.uea.ac.uk/aim/aim.php.

Thank you Sir,

Yes, In my limited knowledge I feel AIM-II is suited for multi-component modelling. But, I don' think it accounts for certain ions, like K+ in the varying chemical composition mode. There might be exceptions in the model here.

Also, these models are based more on thermodynamics, which helps predict deliquescence effectively, but the kinetic (nucleation rate driven) process of efflorescence being dependent on many parameters are difficult to model. Perhaps that's why in the Book by Seinfeld and Pandis (Atmospheric Physics and chem..from Air Pollution to Climate Change) it is mentioned that it is better to derive Efflorescence Relative Humidity (ERH) experimentally.

In my limited knowledge I feel the supersaturation in two-component salt systems are derived from their bulk solubility (Pitzer...ZSR models) phase diagrams which are usually calculated from thermodynamic equilibrium. Do these solubility calculations have approximations for short range ionic interactions and the common-ion effect in the AIM or other models?

My question is that that during dehydration (reducing RH and hysteresis effect) in the confined volume of the droplets, if there is a common anion (e.g Cl-) is it possible that the solubility of the two salts deviate from the thermodynamic predictions and the degree of supersaturation in each salt also change?

I suggested ISORROPIA, but, indeed as dr Watson, I have a very good experience with AIM and it has more components

As John Watson suggested, the E-AIM model is a good option. Another model which is accurate for aqueous electrolyte solutions from dilute to highly concentrated conditions at room temperature, is the AIOMFAC model, available online: http://www.aiomfac.caltech.edu/ .

The AIOMFAC model covers 12 different inorganic ions and most of their interactions in aqueous solutions.

Yes, Sir

I have already come across your Model AIOMFAC, and trying to use it as well as AIM. I have also been following the work being done at ETH Zurich for Organic-inorganic mixtures. Thank you for your answer.

I would like to know that since the solute activities and hence supersaturations in inorganic ternary mixtures (with water) are generally extrapolated from relatively dilute solutions are there possibilities of deviations in experimental observations during dehydration of such ternary droplets.

Hi Dr. Gupta,

Concerning extrapolations of models to the highly concentrated composition range based on thermodynamic data in the dilute range: this is an important point to consider when you compare new experiments in the supersaturated region to model results. The choice of model may be critical.

Both the AIM model and the AIOMFAC model are among the best choices for that highly concentrated region since these models were designed to perform reasonably well in that composition range. The two models have also been parameterized based on measurements of supersaturated solution droplets (from electrodynamic balance experiments), therefore, the experimental database for these two models was not limited to dilute aqueous solutions and ternary mixture data was considered as well (see, e.g. Zuend et al., 2008, Atmos. Chem. Phys.).

Dear Dr. Zuend,

Thank you for the details. I will go through your paper. Hoping to have some fruitful discussions with you in future.

The problem is that we are doing the experiments on substrates using Optical Microscopy...so we can't get the exact volume/mass to compare with the models. We can only get the relative 2D area (top-view).