What does it mean to sell flour with a heart that sells white powder?

With the heart of selling white powder, holding the money to sell flour generally refers to thankless work, more work and less gain.

White powder is the general term for heroin and morphine. It is a semi-synthetic drug with morphine alkaloid as the starting point of synthesis, commonly known as ground number, white powder and white flour. It is a fine product in the opium drug series. It generally includes heroin base (diacetylmorphine), heroin salt (including hydrochloride, nitrate, tartrate and citrate, but generally refers to hydrochloride) and heroin salt hydrate.