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I will repeat this experiment with the casein stabilized 320ppm.
Yes, perhaps it is possible that the particles are protected after drying and go back into solution.
But of course it is very time-consuming to evaporate 250ml of liquid to get 80mg Ag in dry Colloidal Silver.
But, the total dry weight are over 1g, as the entire sodium casinate and the reducing agent (glucose) are also contained in it.
If the sodium casinate had the same properties as the sodium protalbinate (keyword: isoelectric point), it would lose its solubility at low pH values and drag the nanoparticles with it, in order to then concentrate them by pouring off the supernatant, purify them and neutralize them again with sodium hydroxide and bring it back into solution.
This means it can be easy cleaned without a centrifuge and then dried in high concentration.
In addition to sodium protalbinate, I was able to achieve this years ago with egg white powder (from the bodybuilding shop). I used 250ml ready-made electrochemically produced colloidal gold 40 ppm, then mixed it with 15 mg of egg white powder and was able to concentrate it with acid precipitation, clean it, neutralize it.
I didn't dry it at the time, but it was 5ml of highly concentrated CG (~2000ppm) which, when diluted to 100ml (~100ppm), gave a beautiful ruby red color and only had an electrical conductivity of 100 µS/cm, so relatively pure and free of reduction residues.
But I have to say this 40 ppm electrolytically produced colloidal gold was reduced with citrate and tanin.