35 Pa. Stat. § 931
On and after the first day of January, one thousand nine hundred and twenty-four, it is unlawful for any person or copartnership or corporation to sell, at wholesale or retail, within this Commonwealth, any caustic acids or caustic alkalies, or preparations containing such acids or alkalies, intended for household use, or mineral or chemical salts for agricultural purposes, without affixing to the bottle, box, vessel, sack, or package containing the same, a label printed or plainly written, containing the name of the article, the name and place of business of the manufacturer, seller, or distributor of such household acids, alkalies, or preparations thereof, and in addition the word "Poison," which shall conspicuously appear thereon in capital letters, not less than twenty-four point size, or which shall be affixed thereto as a sticker conspicuously placed: Provided, That in the case of mineral or chemical salts, including nitrate of soda, sulphate of ammonia, muriate of potash, sulphate of potash, intended or sold for agricultural purposes, the sacks, packages, or other containers, or attached cards or labels, shall have printed thereon, as hereinbefore provided, the words "Poisonous to live stock."
35 P.S. § 931