Note 515 — Chapter XIII · OF POISONING WITH ARSENIC.
Reading edition
The only probable source of such impregnation is pyritic sulphur, which is frequently used abroad, and has of late been occasionally employed in this country, for making sulphuric acid. As pyrites commonly contains arsenic, the acid becomes adulterated with oxide of arsenic, and may communicate the same impregnation to various other reagents which are prepared by means of sulphuric acid. The oxide may easily be detected in that acid by a stream of hydrosulphuric acid gas, after moderate dilution with water; for pure acid is rendered milky; but an arsenical acid yields a yellow precipitate of sulphuret of arsenic.