The reason why the oxalate ion appears to be more toxic than the acid oxalate ion and oxalic acid (Figure 69.1) to at least ruminants is intriguing. The intracellular body pH is around 7 and for oxalic acid the pK 11.27 and the pK 24.28 exists that the double negative ion (of which a 0.1M solution in water has a neutral pH) will bind with Mg2 and Ca2 more readily and forthwith than the acid oxalate ion (0.1M solution in water pH 2.7) and oxalic acid (0.1M solution in water, pH 1.3 (Budavari, 1996)). In the rumen (pH 6.5) both these should, however, be rapidly be changed to the oxalate ion. The fact that the cations (Na,Kand NH4) of the soluble oxalates may differ, should not be a factor either as they will be fully ionized in the rumen.