OXALIC ACID.—Oxalic acid is a caus tic and corrosive poison obtained from cellulose. It occurs as transparent monoclinic crystals (resembling Epsom salts), having a strong acid taste. It is soluble in and in alcohol, and slowly soluble in ether. Of all the irri tant vegetable poisons, oxalic acid is the most important. As it resembles Epsom salts (magnesium sulphate), it may be readily mistaken for it, and as it may be easily procured either as oxalic acid or as salt of sorrel or essential salt of lemon (potassium binoxalate) to remove ink stains or iron-rust, to scour metals, to clean wood, or for use in photography, it is not infrequently taken by accident or with suicidal intent. Common sor rel (oxalis acetosella), containing oxalic acid in combination with potash (potas sium binoxalate), is sometimes used in infusion as a cooling drink or as an ingredient of salads; but such use is not to be commended, as danger lurks therein. A fatal case of poisoning by the use of sorrel has been reported (Hosp. Gaz., June, 'SO).
Oxalate of cerium is the only official preparation of oxalic acid; its descrip tion will be found under CERIU3I.
Poisoning by Oxalic Acid.—When ox alic acid in substance or in strong solu tion is swallowed there is felt a hot, burning, acid taste during its passage downward, followed by pallor, clammy perspiration, violent prostration, intense abdominal pain, usually with vomiting. If the poison be diluted, the vomiting may last a long while. In some cases, however, vomiting is absent; in others it is incessant until death.
The mucous membrane of the mouth, tongue, and throat is whitened, appear ing as though it were bleached. The nervous system appears to be also re motely affected, as, in cases of recovery from oxalic-acid poisoning, spasmodic twitchiugs of the facial muscles, tempo rary loss of voice, numbness, and ting ling of the legs have been observed (Henry C. Chapman). It generally does its work quickly and the corrosive symp toms are replaced by those of fatal lapse. When diluted sufficiently, so as to show no corrosive action, the acid is still highly poisonous, acting as a para lyzer of the heart (Foster). The mini mum fatal dose, according to Taylor, is one drachm. Death may take place very quickly or may be delayed for several days.
Post-mortem examination of case of oxalic poisoning shows oesophagus and duodenum to be parts most affected; the stomach is much less implicated; the oesophagus is corroded in its whole length, the duodenum in places. The corrosions are white or dirty gray, opaque, or bile-stained or brown, from ha'.matin; they are confined to the mu
cosa. The epithelium lining the stom ach is abnormally transparent, with evidence of venous congestion; hremor rhages into or on to the surface of the mucosa are of frequent occurrence. Pre cipitates of crystals or amorphous gran ules of oxalate of lime from white or milky patches on the mucous membrane. Kidneys are hyperaemic, and show cloudy swelling and deposits of crystals of ox alates in the contorted and straight tubules. Like the mineral acids, coagu lation of the blood is produced, but as the blood-casts in the submucous vessels of the oesophagus and stomach always contain crystals of oxalate of lime, diag nosis is easy. Hans 'Reich° (Friedr. Bl. f. ger. Med., vol. xlviii, pts. 3 and 4, '97).
Treatment of Poisoning by Oxalic Acid.—To be efficacious, the treatment should be prompt and assiduous. After evacuating the stomach by emetics and siphon or stomach-pump, chalk (calcium carbonate), magnesia, and plaster-scrap ings from the wall should be given, well stirred in water. Alkalies and their car bonates should not be given, however, under any circumstances, as the salts formed would be as poisonous as the oxalic acid.
Case of oxalic-acid poisoning in a boy, aged 15 years. Seen 12 minutes after the poison had been swallowed, patient was unconscious, markedly pallid and clammy, and extremities cold. Radial pulse could not be felt. Pupils were fairly dilated. Jaw was fixed in tetanic spasm, and froth exuded from between the teeth.
One-tenth grain of apomorphine was injected hypodermically; a stomach siphon-tube was introduced after the jaws had been pressed apart, and a pint of warm water was placed in the stom ach, but immediately expelled. Vomit ing continued, and consciousness re turned. The boy now was given 'I, ounce of powdered chalk. suspended in water, and this also was shortly ejected. Recovery proceeded under stimulation. The quantity of poison taken was up ward of drachms. F. J. Lorimer Hart (Lancet, Oct. I, '98).
Therapeutics. — Poulet proposed the use of this drug in asthma, capillary bronchitis, and tuberculous bronchitis. In some cases where oxalic acid was given in doses F. IV. Talley observed that it caused nausea, gia, and an eruption resembling urti caria. Talbot Jones has reported four cases in which acute articular rheuma tism was apparently produced by longed contact with a solution contain ing oxalic acid.
Generally speaking, however, oxalic acid is more interesting on account of its effects as a toxic agent than as a remedial one.