Introduction
● Mineral acids are those that are derived from inorganic compound and its dissociation to produce hydrogen ions in water.
● Generally, mineral acids are very strong and highly corrosive in nature in concentrated form.
● They destroy the tissues when they are come into contact with highly corrosive acids.
● The internal administration of the concentrated acids produces intense burning pain from mouth to stomach, intense thirst.
● It is soluble in water.
● It is used in the formation of electrolytic cells.
● They also used for commercial purposes.
● It also act as irritants when it is in diluted form but as stimulants when well diluted.
● The common mineral acids are sulphuric acid, hydrochloric acid and nitric acid.
Mode of Action
● In concentrated form, minerals acids acts as corrosive and in dilute form, they act as irritant poison.
● These acids act mainly at local site of application with minimal remote or systemic action.
● Mineral acids are powerful desiccants. When these agents come in contact with body, they extract water from the tissue and liberate heat. The acid precipitates the protein and causes coagulation necrosis of the tissue in contact. They fix, destroy and erode the tissue.
● Then it Converts hemoglobin to hematin.
● There is formation of eschar, which has self-limiting effect, and formation of eschar minimizes the further damage of tissue. Thus, due to precipitation of proteins and formation of eschar, the acids do not penetrate tissue much deeper and causes less damage than alkalis.
● Acids cause more damage to the stomach than that of Oesophagus. Squamous epithelium of Oesophagus is more resistant to acids and Columnar epithelium of stomach is susceptible for acids and causes gastric outlet obstruction.
● The pyloric spasm induced by the presence of acid in stomach results in maximum damage to pylorus and pyloric antrum.
Pathophysiology
The following phases is identified after ingestion of mineral acids-
- Inflammatory stage
- Granulation stage
- Perforation stage
- Cicatrization stage
Sign of Symptoms
- Pain in mouth, throat and abdomen
- Dribbling of saliva
- Eructation
- Retching
- Vomiting
- Hematemesis
- Dysphagia
- Dysarthria
- Dyspnea
Acute Poisoning
- Massive gastric hemorrhage.
- Bronchopneumonia
- Perforation of stomach.
- Perforation peritonitis.
- Transient laryngeal edema.
- Infection/sepsis.
- Renal failure
- Shock.
Delayed (Chronic) Poisoning
- Gastric outlet obstruction/pyloric stenosis.
- Malnutrition.
Medico legal Aspects
- Accidental poisoning mar arise mistaken for medicine, industrial, etc
- May be thrown over face or body with malicious intention.
- Suicidal cases are rare.
Sulphuric Acids
Nature
- Also known as oil of vitriol.
- Pure sulphuric acid is heavy, oily, colourless, odourless and non-fuming liquid.
- It is Hygroscopic.
- It carbonizes organic substances.
- It is usually brown and dark in colour.
Fatal dose: 5 to 10 ml
Fatal period: 12 to 18 hours.
Uses
● It is used as a feedstock in the manufacture of a number of chemicals.
● It is used in storage batteries as an electrolyte.
● Sulfuric acid is also used in the leather, fur, food processing, wool, and uranium industries for gas drying.
● It is used as a laboratory reagent.
Mode of Action
- Produces coagulation necrosis of tissues on contact.
Sign and Symptoms
- Burning pain from the mouth to the stomach.
- Abdominal pain is often severe.
- Intense thirst.
- The vomitus is brownish or blackish in colour due to alter’ blood.
- Charred wall of the stomach may also seen.
- There is coincidental damage to the larynx during swallowing.
- Tongue and lips is usually swollen, and blackish or brownish in colour.
- Teeth become chalky white.
- Constipation is severe.
- The voice becomes hoarse and husky
- The eyes are sunken and the pupils usually dilated.
- Perforation in stomach also seen.
- Circulatory collapse.
- Spasm or oedema of glottis.
Post mortem Findings
● Corrosion of chin, angle of mouth, lips, oral mucosa, tongue, throat.
● Corrosion over hands may be noted.
● Teeth chalky white.
● The corroded area of skin or mucous membrane appear brownish or blackish (due to chemical charring of the affected tissue) .
● Perforation of stomach may be seen.
Detection and Forensic Examination
● Litmus test: The pH of the saliva can be tested with a litmus paper to determine whether the chemical ingested is an acid or an alkali (turns red in acid, and blue in alkaline solution).
● Fresh stains in clothing may be tested by adding a few drops of sodium carbonate. Production of effervescence (bubbles) is indicative of an acid stain.
● If vomitus or stomach contents are available, add 10% barium chloride. A heavy white precipitate forms which is insoluble on adding 1 ml nitric acid.
Medico Legal Aspects
- Vitriolage- Vitriolage means throwing of acid on the face or body of a person with a malicious intention to cause bodily harm or disfigurement or to cause blindness.
- Accidental poisoning may arise from mistaken identity since sulfuric acid resembles glycerine and castor oil.
- Homicidal and suicidal cases are rare.
Nitric acid
Nature
- Also known as Aqua fortis, Azotic acid, Engraver’s acid, Hydrogen nitrate.
- Nitric acid is Clear, colourless.
- It is yellowish fuming liquid due to xanthoproteic reaction.
- It has pungent odour.
Fatal dose: 10 to 15 ml
Fatal period: 12 to 24 hours.
Mode of Action
Nitric acid is a powerful oxidising agent and reacts with organic matter to produce trinitrophenol, liberating nitrogen monoxide (xanthoproteic reaction). Corrosion is less severe when compared to sulfuric acid.
Sign and Symptoms
- Corroded areas appear yellowish due to xanthoproteic reaction.
- Stains on clothing and teeth also appear yellowish.
- More severe eructation and abdominal distension due to gas formation.
- Perforation of GI tract may be seen.
- Inhalation of fumes can produce coughing, rhinorrhoea, lacrimation, dyspnoea, and pulmonary oedema.
Detection
● Litmus Test.
● Drop a small piece of copper into the stomach contents and heat it. Pungent, dark brown heavy fumes will emanate that indicates nitric acid is present in sufficient concentration.
Post mortem Findings
- Corrosion of skin, angle of mouth, lips, mucosa with yellowish discolouration.
- Stomach wall is soft and friable, ulcerated.
- Perforation is less common.
Hydrochloric Acid
Nature
- Also known as Muriatic acid and Spirit of salts.
- Hydrochloric acid is Colorless, odourless, volatile, fuming liquid.
- It may acquire yellowish tinge when exposed to air.
Fatal dose: 15 to 20 ml
Fatal period: 18 to 30 hours.
Uses
- It is used as Bleaching agent (less than 10% HCl).
- It is used in Dyeing industry.
- It is used for Metal refinery.
- It is also used as Flux for soldering.
- It is also used in Metal cleaner, drain cleaner.
- It is used as Laboratory reagent.
Sign and Symptoms
- It is less corrosive in its action than sulphuric acid.
- It readily destroys mucous membrane.
- The mucous membrane is at first grey or grey-white, and later becomes brown or black, due to the production of acid haematin.
- Intense irritation of throat and lungs.
- Conjunctivitis
- corneal ulcer
- pharyngitis
- Inflammation of gums and loosening of teeth.
Detection
● Litmus test.
● A solution of silver nitrate produces a heavy, curdy, white precipitate of silver chloride which indicates hydrochloric acid is present in sufficient concentration.
Post mortem Findings
- The skin or mucous membrane shows corrosion.
- The skin may be brownish discolored and parchment like.
- Coagulation of the surface of the tongue and the mucosa of pharynx and esophagus may be seen.
- Stomach is soft, edematous, congested, and desquamated or may be ulcerated.
- Perforations are less common.
- Inflammation and edema of respiratory passage.
Hydrofluoric Acid
● Hydrofluoric acid is a colourless, fuming liquid.
● It is a unique acid, in that most of its toxicity is due to the anion, fluoride, and not to the cation, hydrogen.
● When undiluted hydrofluoric acid is a strong acid and upon dilution, hydrofluoric acid is only weakly acidic at 0.1M.
Uses
● Used in Industry as 90% solution: petroleum refining, pharmaceutics, and germicides and 10% solution: tanning, glass and metal etching, and rust removal.
● It is used as Laboratory chemical.
● It also used in Window cleaning.
Fatal Dose
Unclear, but is probably in the range of 10 to 15 ml.
Mode of Action
● Hydrofluoric acid burns result in severe progressive tissue and bone destruction, and invades deeper tissue planes.
● The fluoride ion then proceeds to affect tissue integrity and metabolism in 3 ways such as Liquefactive necrosis, Decalcification and destruction of bone and Production of insoluble salts—calcium and magnesium fluoride.
Sign and Symptoms
- Severe burning pain in GIT tract.
- The fluoride ion may cause decalcification and corrosion of bone beneath the area of dermal burn.
- Throat irritation
- cough
- Dyspnoea
- Cyanosis
- Lung injury
- Noncardiogenic pulmonary oedema.
- Vomiting
- There is often haemorrhagic gastritis and frank haematemesis.
- Refractory ventricular fibrillation
- Cardiac arrest
References
- Dr. K.S. Narayan Reddy. The essential of forensic medicine and toxicology.34th edition.
- VV Pillay. Modern medical toxicology.4th edition.
- R.K.Sharma. Concise textbook of forensic medicine and toxicology. 3rd edition.
