Table 3.
Common magnesium supplements and their solubilities. Table includes pKa values for the terminal carboxylic proton (pKa1) and the amino proton (pKa2). Backbone protons are displayed as pKa3. The asterisk (*) represents the pKa of the first and second protons to be lost from the diacid sulfuric acid and the subsequent anion bisulfate, and the double asterisk (**) represents the pKa of the proton farthest from the backbone alcohol of the dicarboxylic acid malic acid.
| Form (Oxide/Salt/Chelate) |
Acid/Base Chemistry | Solubility (g/100 mL H2O) |
MW g/mol (%Mg) | Reference |
|---|---|---|---|---|
| Magnesium oxide | Alkaline | 0.010 | 40.30 (60.3) | [75] |
| Magnesium citrate | Acidic (pKa1 = 3.13) | 20 | 214.41 (11.3) | [37] |
| Magnesium chloride | Neutral | 56.0 | 95.21 (25.5) | [76] |
| Magnesium sulfate | Acidic (pKa1 = 3.0; pKa2 = 1.99 *) |
35.7 | 120.37 (20.1) | [75] |
| Magnesium orotate | Acidic (pKa1 = 2.83) | Slightly soluble | 334.48 (7.2) | [66] |
| Magnesium taurate | Acidic (pKa1 = 1.50) | Slightly soluble | 272.57 (8.9) | [77] |
| Magnesium aspartate | Acidic (pKa1 = 1.88; pKa2 = 9.60; pKa3 = 3.65) |
4.0 | 288.49 (8.5) | [78] |
| Magnesium threonate | Acidic (pKa1 = 3.4) | Soluble | 294.50 (8.3) | [79] |
| Magnesium malate | Acidic (pKa1 = 3.46; pKa2 = 5.10 **) |
Slightly soluble | 156.37 (15.5) | [80,81] |
| Magnesium hydroxide | Alkaline | 0.00069 | 58.32 (41.7) | [75] |
| Magnesium carbonate | Weakly alkaline | 0.18 | 84.31 (28.8) | [37] |