Section 25. A corporation may, by a vote of three fourths of its general stockholders at a meeting duly called for the purpose, issue special stock, the total amount of which outstanding at any time shall not exceed two fifths of the actual capital paid in on the general and special stock, and shall be subject to redemption at par after a fixed time which shall be expressed in the certificates. Holders of special stock shall be entitled to receive, and the corporation shall be bound to pay thereon, a fixed half yearly sum or dividend, which shall be expressed in the certificates, not exceeding four per cent, and they shall not be liable for the debts of the corporation beyond their stock.