OXALIC ACID 467 Fatal Dose. — The average fatal dose is four drachms. The smallest recorded fatal dose is one drachm of the solid acid which proved fatal to a boy, sixteen years old. Recoveries have taken place on prompt adminis- tration of remedies after an ounce and two ounces had been swallowed. Fatal Period. — The shortest recorded periods are three minutes and ten minutes. The usual period is one tc^wo hours. Death may be delayed for several days. j^B Treatment — Give chalk, calcinSRiagnesia, whiting or plaster from a wall in a small quantity of water or milk with a view to neutralizing the acid and forming insoluble calcium oxalate. A saccharated solution of lime is considered the best form of treatment. Alkalies or their carbonates must not be administered as they unite with oxalic acid, and form soluble poisonous salts. Large draughts of water should also be avoided as they dissolve the! poison, and thus increase its rapid absorption. After the acid is neutralized in the stomach, vomiting may be promoted by emetics, or the stomach may be washed out very cautiously, and the bowels may be relieved by an eriema or by a purgative, preferably castor oil. Calcium gluconate 10 per cent or calcium chloride 5 per cent may be given. intravenously. The usual symptomatic treatment must then be followed- Infusion23 of an isotonic or hypertonic solution of glucose has been recom- mended, as retention of urea seems to be the principal disturbance, Coutt ascribes to this1 the cramps and convulsions often observed in such cases. Post-mortem Appearances. — If oxalic acid has been taken in a concen- trated form, the marked signs of corrosion are found in the mouth, throat, oesophagus and stomach. Their mucous membranes are white and shrivelled, I and are easily detached from the underlying tissues. They may sometimes be found black in colour from altered blood. The inner surface of the oesophagus is corrugated and shows longitudinal erosions. The stomach contains a dark brown, grumous liquid, acid in reaction. The blood vessels are seen as dark brown or black streaks over its internal surface. Perfora- tion of the stomach is rare, though the walls are often softened and easily torn. The stomach may be pale and not corroded if death has occurred immediately after taking the poison. The intestines generally escape, but the upper part of the duodenum may be affected. The kidneys are congested and loaded with oxalates. If the acid is very diluted there will be signs of local irritation? viz. redness, congestion and inflammation of the mucous membrane. If the effects are only narcotic there will be congestion of the lungs, liver, kidneys and brain, without any local appearances. In the case 24 of a Parsi who committed suicide with oxalic acid, the mucous mem-! branes of the mouth and oesophagus were whitened, soft and easily stripped off. The mucous membrane of the stomach was corroded, and its whole thickness was perforated in one place. The interior of the stomach and its contents were blackened. The intes- tines were grey and gangrenous looking. Chemical Analysis. — To separate oxalic acid the organic mixture may be dialysed, or may be boiled and filtered. To the filtrate is added acetate of lead, when a precipitate of lead oxalate is formed. The precipitate is washed with water and in the watery solution a current of hydrogen sulphide is passed for about half an hour, so that a black precipitate of lead sulphide is thrown down. The black precipitate is now filtered, the filtrate is heated' to remove any excess of hydrogen sulphide and is evaporated to dryness, when the crystals of oxalic acid are found which can be tested by 23. Revista Medico, Latino-Americana, Bt^einos: Aires, July 1925, p. HIS * Jbttr, Amefj Med. Assoc,, Oct. 10, 1925, p. 1170, 24. Bombay Chemical Analyser's Annual Report* J923* p. 3.