For biomass quantification in biofilms I want to prepare a crystal violet (CV) solution. Protocols for this state to prepare a 0.1% CV solution, diluted with a 1% ammonium oxalate solution (aqueous), as also suggested by Hucker (1921). This is similar to classic Gram-staining solutions (Huckers Gram-stain; https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/documents/925/051/115940-en.pdf).

However, I have trouble to prepare the ammonium oxalate solution 1 %, aqueous. Mixing 1.0 g di-Ammonium oxalate monohydrate with 99ml dest. water, results in a solution with fully undissolved white crystals. The ammonium oxalate seems to not getting into solution at all. Also, increasing the temperature has no effect.

Is there any trick, to bring the Ammonium oxalate monohydrate into solution, or has anyone faced a similar problem?

Chemical used is di-Ammonium oxalate monohydrate 99.0-101.0% ACS

(Supplier: Thermo Scientific).

https://no.vwr.com/store/product/en/2346779/di-ammonium-oxalate-monohydrate-99-0-101-0-acs