All persons in the employment of the government of the District of Columbia having, as a result of such employment, custody of or chargeable with property, other than real estate, belonging to the District of Columbia, shall, at such times and in such form as the Mayor of the District of Columbia shall require, make returns to said Mayor of all such property remaining in their possession, and the condition thereof, and, with reference to all property that may have come into their custody that shall have been consumed in use, a statement showing the quantity thereof and the purpose for which used.