As the pKa1 of malic acid is 3.4, it may be that the partially neutralized malic acid salt is less soluble than the acid or the fully neutralized salt.
The pKa2 of malic acid is 5.1. Contact the people at Hampton Research https://www.hamptonresearch.com/contact_us.aspx and ask them. They sell it as a 3.0 M solution, pH neutralized to 7.0. It is possible that you need to fully neutralize it before it turns clear, or that you may also need to gently heat it. Diana ************************************************** Diana R. Tomchick Professor Departments of Biophysics and Biochemistry University of Texas Southwestern Medical Center 5323 Harry Hines Blvd. Rm. ND10.214A Dallas, TX 75390-8816 diana.tomch...@utsouthwestern.edu<mailto:diana.tomch...@utsouthwestern.edu> (214) 645-6383 (phone) (214) 645-6353 (fax) On Jun 8, 2017, at 9:54 AM, Sebastiano Pasqualato <sebastiano.pasqual...@gmail.com<mailto:sebastiano.pasqual...@gmail.com>> wrote: Dear all, we’ve recently having trouble preparing a 3 M stock solution of DL-Malic Acid, pH 7 (which we had, so it’s doable!). When we reach pH 3 - 4 the solution turns milky white and does not goes back to a clear solution even when the pH is raised. Does anybody have any advice on how to get a clear solution? Has anyone gone through the same? Thanks in advance, ciao, Sebastiano -- Sebastiano Pasqualato, PhD Crystallography Unit Department of Experimental Oncology European Institute of Oncology IFOM-IEO Campus via Adamello, 16 20139 - Milano Italy tel +39 02 9437 5167 fax +39 02 9437 5990 web http://is.gd/IEOXtalUnit ________________________________ UT Southwestern Medical Center The future of medicine, today.
