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:
Acetoacetic acid widely used in the production of arylide yellows and diarylide dyes. Although the esters can be used in this reaction, diketene also reacts with alcohols and amines to the corresponding acetoacetic acid derivatives in a process called acetoacetylation. An example is the reaction with 2-aminoindane: Acetoacetic acid is measured in the urine of people with diabetes to test for ketoacidosis and for monitoring people on a ketogenic or low-carbohydrate diet, This is done using dipsticks coated in nitroprusside or similar reagents. Nitroprusside changes from pink to purple in the presence of acetoacetate, the conjugate base of acetoacetic acid, and the