The word “purchaser,” as used in this chapter, embraces every person to whom any estate or interest in real estate is conveyed for a valuable consideration and every assignee of a mortgage, lease, or other conditional estate. The word “conveyance,” as so used, includes every instrument in writing whereby any interest in real estate is created, aliened, mortgaged, or assigned or by which the title thereto may be affected in law or in equity, except wills, leases for a term not exceeding three years, and powers of attorney.