Nitric acid rises to 1 at a temperature of 250 °C. Nitric acid can act as a base with respect to an acid such as sulfuric acid: The nitronium ion, , is the active reagent in aromatic nitration reactions. Since nitric acid has both acidic and basic properties, it can undergo an autoprotolysis reaction, similar to the self-ionization of water: Nitric acid reacts with most metals, but the details depend on the concentration of the acid and the nature of the metal. Dilute nitric acid behaves as a typical acid in its reaction with most metals. Magnesium, manganese, and zinc liberate H:
Methylmalonic acid Methylmalonic acid Methylmalonic acid (MMA) (conjugate base methylmalonate) is a dicarboxylic acid that is a "C"-methylated derivative of malonate. The coenzyme A linked form of methylmalonic acid, methylmalonyl-CoA, is converted into succinyl-CoA by methylmalonyl-CoA mutase, in a reaction that requires vitamin B as a cofactor. In this way, it enters the Krebs cycle, and is thus part of one of the anaplerotic reactions. Increased methylmalonic acid levels may indicate a vitamin B deficiency. However, it is sensitive (those with the disease almost always test positive) but not specific (those that do not have the disease do not always test negative).