The way I have done it (and it was sort of fun in a mad scientist way) was to mix up solid DL-malic acid and sodium hydroxide in the right amounts and add water as needed. This generates <a lot> of heat, but gets around the solubility minimum which is impossible to get out of:
I mixed 40.23 g of DL-malic acid powder (MW=134.1) with 24g of NaOH pellets (MW=40) in a large beaker with a stirrer bar. Put the beaker in a larger container of ice, and put that on a stirrer in the cold room. Add 80 mL H20 to the beaker containing the chemicals, stand back - lots of heat evolved. when everything has quietened down, make up to 100 mL with water (we filtered through a 0.22 um filter). Cheers, Janet -----Original Message----- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Edward A. Berry Sent: Friday, 9 June 2017 2:53 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] preparing DL-Malic acid stock solution (di)Sodium D,L-malate is available from Sigma-Aldrich (# CDS023113) and probably dissolves to give a 3M solution which is slightly alkaline. If pK2 is 5.1, then an insignificant amt of malic acid should bring the pH down to 7 (If you have to add a significant amount, just add more water to dilute to a final conc of 3M Malate + Malic acid) On 06/08/2017 12:32 PM, Diana Tomchick wrote: > 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 > > > > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > > UTSouthwestern > > Medical Center > > The future of medicine, today. >
