Science Buddies: "Ask an Expert"

Hi Science Buddies,

I am currently working on an experiment that involves preparing 3% w/v chitosan in 1% v/v acetic acid solution. Concurrently, I am preparing a solution of 50mM of silver nitrate and dissolving it in 40 mL of distilled water. After both solutions have dissolved, I will mix them and carry out a reduction reaction by heating in a microwave oven at full power (500 W for 6.4 minutes).
However, after I let the chitosan dissolve for three days, (which is what the protocol entails) it has not fully dissolved. In fact, most of the chitosan is still undissolved in the solution. I was wondering if there was another, simple (no high-tech scientific equipment; remembering I am a high school student) way to create or dissolve the chitosan solution.

Thank you,
Annie

Annie,
It could be that the solution of 3% w/v of chitosan in 1% v/v of acetic acid is weak and so the resulting undissolved chitosan. You might want to check the pH and try using a higher strength solution. You might also want to add a magnetic stirrer to stir the solution (to allow the chitosan to be mixed). There are also other acids you can try such as L-ascorbic acid and lactic acid.

Thank you for your prompt response. I will try to obtain a magnetic stirrer. I read about that in an article, and now that you mention it I think I will try to purchase one.
In terms of units, how much more acetic acid should I add? I'm thinking 4 mL would suffice, since I added 4 mL at the beginning. If you think it should be greater than or less than this amount, please let me know.
Thank you again.

I will suggest starting with one variable at a time. You might want to start with the stirring. Optionally for stirring, you can try making the solution in a bigger flask (to avoid spilling) and putting it on a shaker (gentle shaking and making sure it will not move). How much acetic acid to use will depend on how much chitosan you use and the solubility. You may start with four mL since it is what you used and then try a higher or lower volume and if it doesn't work, then maybe a stronger strength solution of acetic acid.

Good luck on your experiment!

Thank you so much!

You're welcome, Annie! Good luck on your experiment!