The item “commodities” when used in an appropriation Act, means and includes expenditures in connection with current operation for the purchase of articles of a consumable nature which show a material change or appreciable depreciation with first usage and equipment having a unit value not in any instance exceeding $100, but does not include any expenditure for library books, any expenditure for replacement fixtures or repair parts in connection with the repair and maintenance of property or equipment or expenditures included in “permanent improvements” as defined in Section 21, “operation of automotive equipment” as defined in Section 24.2, and “telecommunications services” as defined in Section 24.3.