Pen. Code, § 382

Every person who adulterates or dilutes any article of food, drink, drug, medicine, spirituous or malt liquor, or wine, or any article useful in compounding them, with the fraudulent intent to offer the same, or cause or permit it to be offered for sale as unadulterated or undiluted; and every person who fraudulently sells, or keeps or offers for sale the same, as unadulterated or undiluted, or who, in response to an inquiry for any article of food, drink, drug, medicine, spirituous or malt liquor, or wine, sells or offers for sale, a different article, or an article of a different character or manufacture, without first informing such purchaser of such difference, is guilty of a misdemeanor; provided, that no retail dealer shall be convicted under the provisions of this section if he shall prove a written guaranty of purity obtained from the person from whom he purchased such adulterated or diluted goods.