Sodium Chloride aqueous solution for viscosity adjustment of anionic systems

MaydayMayday Member
edited March 15 in Formulating
I have started working with gellan gum thickened with sodium chloride as a gelling agent because it has a very attractive clarity similar to carbomer. However, I noticed that solid crystals of kosher salt cause agglomerates to form—the local concentration near the crystals is high enough to gel as it dissolves, before it can disperse.
I'm thinking incorporating salt gradually with a dropper of known concentration will make it possible to do gradual viscosity adjustment in the lab, rather than having to do a "salt curve" of sorts with gellan gum alone.
What minimum percentage of sodium chloride in distilled water would be self-preserving without other additives? Are there any hazards to watch out for, such as the growth of salt-tolerant extremophiles? Is this a common practice, or am I doing something strange?
Additionally, is food-grade kosher salt generally fine for cosmetic formulation? This article states that the Diamond Crystal Kosher Salt I'm using has a sodium chloride purity of 99.83%. What is the likely composition of the remaining 0.17%? Potassium Chloride?
I've currently got a 35% kosher salt solution (26.9g salt, 50g water) on my magnetic stirrer hot plate. This is theoretically below the solubility limit of sodium chloride in water at 0°C, but is not dissolving adequately.
⚠️ I have a lot of ideas, but not much experience! Please keep this in mind when reading my suggestions. ⚠️

Comments

  • I make 20% solution first for my cleansing products and store some of them.

    How did you dissolve 30% NACL in water and in how much time? 
    I once made a 20kg batch of 30% NACL in water and after 5-10 minutes of mixing it still didn't dissolve completely. 
  • MaydayMayday Member
    edited March 16
    At least 6 hours of stirring on the magnetic stirrer. Added 10% initially which dissolved quickly, then added the rest up to 35%.
    Looking at the solubility on PubChem again, I misinterpreted the values. It's 36.0g NaCl to 100g H20. That's actually 26.47% NaCl out of 136g total. I have an additional 8.9g NaCl beyond saturation point.
    Will try a 25% solution and see if that dissolves properly. If not, 20% will be fine.
    ⚠️ I have a lot of ideas, but not much experience! Please keep this in mind when reading my suggestions. ⚠️
  • That is good to know. I will try 25% too. 

    20% dissolve in 3-4 minutes
  • MaydayMayday Member
    25% fully dissolved at 6m30s with low speed vortex on magnetic stirrer. Most of it was already dissolved by 5m.
    ⚠️ I have a lot of ideas, but not much experience! Please keep this in mind when reading my suggestions. ⚠️
  • Mayday said:
    25% fully dissolved at 6m30s with low speed vortex on magnetic stirrer. Most of it was already dissolved by 5m.
    Thanks for sharing
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