 oxalic acid and its salts are used in industry as bleaching agent
and in calico printing
 Its household use for bleaching has made it a dangerous
substance
 Solutions containing oxalic acid cause falling off hair when
poured on the head
 Oxalic acid is sometimes used to erase writing in attempts at
forgency
Prepared by
Dr. Amina Rao
K.M.S Medical College ,Sialkot
Difference between organic and
inorganic acids
Organic acids differ from inorganic acids in two
major respects:
1) They are weaker in action
2) They are usually absorbed into circulation and
so have both local and remote action
organic acid
• Important poisons are oxalic, carbolic, acetic and
salicylic acids.
• They have powerful rapid action
• They act as strong irritants locally and also
possess a powerful remote action after absorption
Oxalic acid
Oxalic acid is a corrosive acid.
Oxalic acid is a constituent of many house hold
products. It is found in many disinfectants, household
bleach, metal cleaning liquids, antirust products and
furniture polishes.
Oxalic acid is found in several green leafy vegetables
such as spinach, rhubarb, Brussels sprouts, broccoli,
carrots , cabbage lettuce etc. It also occur in fruits
such as berries , concord grapes, figs, and plums
etc. along with in some seeds, nuts and grains.
physical appearance
oxalic acid is crystalline substance resemble in
appearance with magnesium sulphate and zinc
sulphate. It can be differentiated as
features
taste
oxalic acid
Sour and acidic
mgso4
Bitter and
nauseating
nce
znso4
Bitter and
metallic
reaction
Strongly acid
neutral
Slightly
acid
Heat
sublimes
Not so
Not so
Sodium
carbonate
Effervescence but no
ppt
No
effervescence
but white ppt
No
effervescence
but white ppt
Ink or
iron stain
bleaches
Not so
Not so
Signs and symptoms
The character and severity of symptoms depend upon the
amount and conc. Of acid taken.
 it has two distinct effects
1. Local effect
2. Remote effect
e.g. shock, hypocalcemia and renal
damage
A. Local effect:

It readily corrodes the mucous membrane Of the
alimentary tract but rarely the skin.
REMOTE EFFECT
 A large concentrated dose would kill with in a couple
of hours by shock or hypocalcaemia (lowering of
calcium levels in the blood).
 A large dilute dose would cause kidney failure
 Large doses causes rapid death from
shock(narcotic effect).
• There is a sour taste in the mouth and burning sensation
in throat and stomach.
• This is followed by persistent vomiting. Vomit is black in
color (coffee ground)due to altered blood
If in a case of short duration, the intestinal tract is not
affected but when life is prolonged
There is pain and tenderness over the
abdomen, purging and tenesmus may
appear after absorption, collapse may
occur.

 Oxalic acid in circulation react with free Ca in plasma to form
Ca oxalates crystals causing dec. in free Ca in plasma inducing
hypocalcaemia. Numbness and tingling indicate the effects of
hypocalcaemia on the nervous system.
Spasmodic twitching of the muscles of the face and extremities
and even convulsions may be followed.

oxalic acid has a nephrotoxic
action and irritation of kidneys
may be found
 There may be oliguria and urine contains albumin,
blood and Ca oxalate crystals.
 Presence of oxalic acid crystals in the urine is termed as
oxaluria
Precipitation of calcium oxalate in the
renal system (proximal tubules of the
kidney) may lead to local necrosis of the
tubular epithelium, producing kidney
dysfunction and electrolyte imbalance. In
renal tubular injury the path physiological
factors at the cellular level are considered to
be energy depletion, cell swelling, calcium
influx, intracellular acidosis and enzyme
activation .
 Obstruction of the renal tubules by the
crystals is also a mechanism of renal damage
 Fatal Dose
The average fatal dose of the poison is about
15-20gmsthe smallest recorded fetal dose is
5 gms
 Fatal
Period
Death usually occurs within an hour.
The longest recorded period is 5 days.
Treatment
1 Gastric Lavage
wash the stomach using limewater. A soft
stomach tube can be passed with care. Warm
water should not be used as it dissolve more
acid.
2. Antidote
Antidote is any Ca preparation which converts
the poison into insoluble Ca oxalates.
A suspension of 30gms of chalk in water or
milk will neutralize about 20gms of oxalic
acid.
Alkalis such as soda, potash and ammonia should not be
given as their oxalates are insoluble
 Ca Gluconate may be given by mouth
Or 10ml of a 10% solution intravenously
 In severe cases, parathormone extract
Should be given
 The rest of the treatment is symptomatic.
example
A 50 years old woman swollen about 30gms of oxalic acid in
beer. In half an hour, she complained of burning pain in
stomach and was found rolling about. Chalk and water was
freely given and she recovered
Postmortem
appearance
• The mucous membrane of the tongue, mouth, throat
is commonly white as if bleached but is sometimes
reddened by irritation. Lips and chin don’t show
staining
 EFFECTS ON STOMACH
o The stomach contains a dark brown gelatinous liquid
due to the formation of acid haematin.
o The mucous membrane is corroded and detached in
varying degrees depending upon the conc. Of acid
 Perforation however is rare. The blood vessels in submucosa
layer may be seem distinctly as dark lines due to acid
haematin. The outer coat of the stomach may be inflamed.
 If the effect are only narcotic, there will be congestion of
lung, liver, kidney and brain without any local changes
where death has been delayed. Inflammation will be found
on the upper portion of the small intestine and the kidney.
Medicolegal aspects
 Accidental poisoning is due to being mistaken for MgSO4 or
sodium bicarbonate
 Oxalates occur in the leaves of rhubarb and have caused
poisoning when the leaves are used as safe vegetables
 Oxalic acid is sometimes taken with suicidal intention but
rarely used for homicide on account of its sour taste and rapid
action
 oxalic acid and its salts are used in industry as bleaching agent
and in calico printing
 Its household use for bleaching has made it a dangerous
substance
 Solutions containing oxalic acid cause falling off hair when
poured on the head
 Oxalic acid is sometimes used to erase writing in attempts at
forgery