Microbiology

1. DEPARTMENT OF FORENSIC MEDICINE AND TOXICOLOGY
SEMINAR
ON
OXALIC ACID POISONING
GUIDED BY -DR.SUNITA WAGH .
PRESENTED BY - Ankita Rajesh Kharat

2. OXALIC ACID
❑ PROPERTIES
➢Oxalic acid is a corrosive acid .
➢It is a crystalline substance, , resembling in appearance Magnesium
sulphate[mgSO4] and zinc sulphate [ZnSO4].

3. OXALIC ACID CAN BE DIFFERENTIATED FROM MGSO4
AND ZNSO4 BY FOLLOWING FEATURES :-
Oxalic acid Magnesium
sulphate
Zinc sulphate
1. Taste Sour and acidic Bitter and
nauseating
Bitter and
metallic slightly
acidic
2. Reaction Strongly acidic Neutral Slightly acidic
3. Heat Sublimes Not so Not so
4. Sodium carbonate Effervescence but
no precipitate
No effervescence
but a white
precipitate
No effervescence
but a white
precipitate
5. Ink or ion stains Bleaches Not so Not so

4. ❑ SIGNS AND SYMPTOMS
Remote effects .
• Local action – it readily corrodes the mucous membrane of the alimentary tract but
rarely the skin .
• Remote action - large dose causes rapid death from shock .
• There is sour taste in mouth and burning in the throat and
stomach , Followed by persistent vomiting .
• The vomit is black in color ‘coffee ground’ due to altered
blood.
• If the case is of short duration , the intestinal tract is not affected ,but
duration is prolonged there is pain and tenderness over the abdomen and
tenesmus may appear.
• After absorption , signs of collapse soon appear.

5. Numbness and tingling indicate the effects of hypocalcaemia on the nervous system .
Spasmodic twitching of muscles of the face and extremities and even convulsions may follow.
Where death is not rapid , evidence of irritation may be found as oxalic acid has a
nephrotoxic action .
There may be oliguria , and the urine contains albumin , blood, and calcium oxalate crystals .
Fataldose
The average fatal dose is about 15to 20 gm .
the smallest recorded fatal dose is 5 gm.
Fatal period
Death usually occurs in an hour.
longest recorded period is 5 days.

6. TREATMENT
o A soft stomach tube can be passed with care and the stomach washed out using lime water .
o warm water should not be used for stomach wash as it may dissolve more acid.
o Antidote is any CA preparation which convert the poison into insoluble CA oxalates .
o a suspension of 30 gm. of chalk in water or milk will neutralize about 20 gm. of oxalic acid.
o alkalis such as soda , potash and ammonia should not be given as their oxalates are soluble.
o Calcium gluconate may be given by mouth or 10 ml of a 10% solution intravenously.
o In severe cases , parathyroid extract should be given .
o Urinary output should be checked to detect the possibility of renal damage and fluid intake
controlled as found necessary .
o The rest of the treatment is symptomatic .

7. POSTMORTEM APPEARANCES
o Lips and chin do not show staining .
o The mucus membrane of the tongue , mouth , throat and gullet is commonly white as if
bleached but is sometimes reddened by irritation.
o the stomach contains a dark brown gelatinous liquid due to the formation of acid haematin .
o the mucous membrane is corroded and detached .
o Perforation is rare.
o Outer coat of stomach is inflamed .
o Congestion of lungs , liver, kidneys and brain , without any local changes .
o Where death is delayed , inflammation will be found in the upper portion of the small
intestine and the kidneys .

8. MEDICO LEGAL ASPECTS
o Oxalic acid and its salts are used in industry as bleaching agents , and in calico printing .
o Its household use for bleaching has made it a dangerous substance.
o Accidental poisoning is due to its being mistaken for magnesium sulphate or sodium
bicarbonate .
o oxalates occur in the leaves of Rhubarb and have caused poisoning when the leaves are
used as safe vegetables .
o Oxalic acid is sometimes taken as suicidal intention but rarely used for homicide on account
of its sour taste and rapid action .
o Oxalic acid is sometimes used to erase writing in attempts at forgery.

9. THANK YOU.