No person, firm, corporation, or agent or employee of any person, firm, or corporation shall manufacture for sale or offer or expose for sale any flaxseed or linseed oil unless the same shall answer all the chemical tests for purity recognized in the United States Pharmacopoeia or offer or expose for sale any flaxseed or linseed oil as "boiled linseed oil" unless in its manufacture the same shall have been put to a temperature of 225 degrees Fahrenheit.