Ans. d. 100 to 200 mg (Ref: Parikh 6/e p9.9; Reddy 33/e p535)Fatal dose of arsenic in adults is 100 to 200 mg.Arsenic PoisoningArsenious oxide (Sankhya or somaikhar) also known as arsenic trioxide (AS2O3) is MC form of arsenic usedQ.Other Arsenic Salts* Copper arsenite (Scheele's green)* Arsenic trisulphide (yellow orpiment or hartal)* Copper acetoarseniteQ (Paris green or emerald green)* Arsenic trichloride (butter of arsenic)* Arsenic disulphide (red realgar or manseel)Fatal dose:100-200 mgQ is fatal doseArsenophagist: Take arsenic regularly as aphrodisiac or tonic can tolerate up to 300 mg dose.Fatal period:Fatal period is 2-3 hours in narcotic form and 12 hours-2 days in gastrointestinal formQ.Patient may die from subacute poisoning in 7-10 days due to heart failure or from chronic poisoning in weeks due to liver or kidney damageQ.Clinical Features:Acute poisoning:Usually manifest within 15-30 minutes after the dose, but may be delayed if arsenic is taken with food; Nausea, burning pain in the esophagus, stomach and epigastrium, severe, persistent vomitingQ.Stools are tinged with blood, watery like the rice water stools of cholera, and contain shreds of mucus membrane and fragments of the poison in three or four hoursQ.Intense thirst is a constant featureQ.Skin eruptions may appear in late stages.Collapse sets in, with cold clammy skin, pale anxious face, sunken eyes, dilated pupils, rapid feeble pulse, and sighing respirations.Convulsions or coma may precede death.Subacute poisoning:In some cases where the patient survives the initial acute attack, the poisoning becomes subacute, the symptoms persisting in lesser degree for some time.The patient becomes progressively weak and may die of heart failure and weakness in 7-10 days.When a large dose of arsenic is taken:Poison is quickly absorbed, the symptoms of gastroenteritis may be absentSymptoms of narcotic poisoning, such as vertigo, headache, spasms, followed by stupor and vascular collapse may be present.Death occurs in 2-3 hours.Tests:Excretion of >100 mg in 24 hours urineQAtomic absorption spectroscopy detectionMarsh's and Reinschs testQ are obsoleteDisadvantages:Delays putrefactionQ and can be found in bones, hair and nails for several yearsQCan be detected in completely decomposed bodies, charred bones or ashesQ.