In each instance where the duties of the sheriff of any county require him, in his official capacity, to incur traveling and hotel expenses, training, or any duty requiring the need of a warrant, for himself or his deputies, he may, prior to the incurring thereof, make demand on the county auditor for a warrant on the county treasurer and shall receive a sum not to exceed the amount set aside under the provisions of section 31-1802, Idaho Code, to be used for the purpose of defraying the whole or a part of said traveling and hotel expenses, training, or any duty requiring the need of a warrant. At the time demand is made on the county auditor for said warrant it shall be the duty of the sheriff to file with the auditor a statement specifying the general purpose for which the sum to be withdrawn is to be used.