Dear friend Boeun Choi

Indium nitrate hydrate is said to be water soluble, but it does not dissolve well both in deionized water and organic solvents above 20 mM. One possible reason for this is that the indium nitrate hydrate is not pure (4.4 Solubility - Chemistry....). Another possibility is that the indium nitrate hydrate is not being dissolved properly. You can try dissolving it in hot water or by adding a small amount of acid (Indium(III) nitrate 99.9 trace metals...).

I hope this helps! Let me know if you have any more questions.

Source:

(1) Indium(III) nitrate 99.9 trace metals 207398-97-8 - Sigma-Aldrich. https://www.sigmaaldrich.com/US/en/product/ALDRICH/326135.

(2) Solvent properties of water (article) | Khan Academy. https://www.khanacademy.org/science/biology/water-acids-and-bases/hydrogen-bonding-in-water/a/water-as-a-solvent.

(3) What Happens When Salt Is Added to Water? | Sciencing. https://sciencing.com/happens-salt-added-water-5208174.html.

(4) How can i dissolve Sodium Nitrate in organic solvents?? - ResearchGate. https://www.researchgate.net/post/How-can-i-dissolve-Sodium-Nitrate-in-organic-solvents.

(5) 4.4 Solubility - Chemistry LibreTexts. https://chem.libretexts.org/Courses/Purdue/Purdue:_Chem_26505:_Organic_Chemistry_I_%28Lipton%29/Chapter_4._Intermolecular_Forces_and_Physical_Properties/4.4_Solubility.

Hi Boeun Choi

In(3+) is quite easily hydrolyzed, with a first hydrolysis pKa at 4.4, which means that in DI water the particles' surface will quickly become covered with less soluble compounds (hydroxide or hydroxynitrate) that will inhibit further dissolution.

You need a slightly acidic solution - maybe 0.01-0.1 M HNO3 (nitric acid so you don't add a different anion). Solubility of indium nitrate in water is high, so the common ion effect is not a concern. (However, you can of course use other acids that will give you a pH around or below 2.)

Kaushik Shandilya Emanuel Cooper Thank you for your answers :)