Effect of pH on Extractability of Calcium and Oxalate from Alfalfa Leaflets

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Abstract
Calcium and oxalic acid were measured in extracts from alfalfa leaflets. HCl (1-0.6 N) resulted in extracts with pH from .7-3.2, respectively. Extracted Ca decreased to 81% of the total at pH 1.3 and then gradually to 65% at pH 3.2. Oxalic acid extraction at pH 1.3 was 33% of that at pH .7 and near nil at pH 3.2. Extracted calcium at or below pH 2.3 was associated predominantly with equivalent extracted oxalic acid. Scanning electron microscopic examination of low-temperature ashed extracted residues demonstrated calcium oxalate crystals in the pH 1.3 residue but not in pH 1.1 residue. Energy dispersive x-ray analysis showed that Ca and P were not associated necessarily in the low-temperature ash. The pH of the bovine digestive tract is discussed.