Acids - Corrosive(Caustic) Poisons

ACIDS

Acids are hydrogen containing substances that on dissociation in water produce hydronium ions. They are potent desiccants with the ability to produce coagulation necrosis of tissues on contact.* There is however eschar (slough) formation which has a self-limiting effect, minimising the extent of further damage. When a strong acid (especially inorganic) is dissolved in a solvent, an exothermic reaction ensues resulting in the emanation of heat which is referred to as the heat ofsolution.** This thermochemical reaction is postulated to bethe cause for eschar formation. It is interesting to note that while generally speaking, the lower the pH of an acid the higher is its corrosive effect, it is not the pH alone which is the determinant of severity. For instance, lemon juice which has a very low pH of 2 is not corrosive in nature at all. More important determinants include molarity, concentration, and complexing affinity for hydroxyl ions.

Ingestion of acid causes more damage to the stomach than the oesophagus because the squamous epithelium of the latter is more resistant to acids, while it is just the opposite in the case of alkali ingestion where the columnar epithelium of the stomach is more resistant. However the current concept is that the minimal oesophageal damage in acid ingestion is more probably because of rapid oesophageal transit and limited penetrating ability, rather than from any special protective properties of the columnar epithelium. Acid burns of the stomach most commonly involve the antrum and pylorus.

Inorganic Acids

Most of the information mentioned in the foregoing section actually pertains to inorganic or mineral acids, while corro-sion is not really a prominent feature of organic acids. But on account of better absorption, organic acids display prominent systemic effects.