The parties may by agreement determine the method of appointment of the arbitrator or arbitration panel. If the parties have agreed upon arbitration under this Article and have not otherwise agreed upon the number of arbitrators or the method for their appointment, the controversy shall be heard and decided by a single arbitrator designated in such manner as the Commissioner of Labor shall determine. Any person or agency selected by agreement or otherwise to appoint an arbitrator or arbitrators shall send by registered mail to each of the parties to the proposed proceeding notice of the demand for arbitration. The arbitrator or arbitration panel, as the case may be, shall have such powers and duties as are conferred by the voluntary agreement of the parties, and, if there is no agreement to the contrary, shall have power to decide the arbitrability as well as the merits of the dispute. (1945, c. 1045, s. 5; 1947, c. 379, ss. 1-3; 1951, c. 1103, s. 1.)