The commissioner may from time to time appoint labor referees for particular disputes under sections 179.18 to 179.25. Such appointment shall be for the duration only of the particular dispute. Such labor referees shall be paid a per diem allowance not to exceed that established for arbitrators in section 179A.16, subdivision 8, while so engaged, and their necessary expenses. When approved by the commissioner, the commissioner shall cause to be paid, from the appropriation to the commissioner, the amount due to the labor referees for services and expenses.