A distiller desiring to withdraw alcohol from bond for de-naturing purposes under the provisions of this act shall, at his own expense, provide a de-naturing bonded warehouse, to be situated on and constituting a part of the distillery premises. It shall be separated from the distillery and the distillery bonded warehouse and all other buildings, and no windows or doors or other openings shall be permitted in the walls of the de-naturing bonded warehouse leading into the distillery, the distillery bonded warehouse or other room or building, except as hereinafter provided. It must be constructed in the same manner as distillery bonded warehouses are now constructed, with view to the safe and secure storage of the alcohol removed thereto for de-naturing purposes and the de-naturing agents to be stored therein. It must be approved by the Commission of Internal Revenue. It shall be provided with closed mixing tanks of sufficient capacity. The capacity in wine gallons of each tank must be ascertained and marked thereon in legible letters, and each tank must be supplied with a graduated glass gauge whereon the contents will be at all times correctly indicated. All openings must be so arranged that they can be securely locked. Suitable office accommodation for the officer on duty must be provided. SEC. 3. The de-naturing bonded warehouse shall be used for de-naturing alcohol, and for no other purpose, and nothing shall be stored or kept therein except the alcohol to be de-natured, the materials used as de-naturants, the de-natured product, and the weighing and gauging instruments and other appliances necessary in the work of de-naturing, measuring, and gauging the alcohol and de-naturing materials. These bonded warehouses must be numbered serially in each collection district, and the words "De-naturing bonded warehouse No.--, district of--," must be in plain letters in a conspicuous place on the outside of the building. In case the distiller's bond has been executed before the erection of such warehouse the consent of the sureties to the establishment of the de-naturing warehouse must be secured and entry duly signed made on the bond." DE-NATURING MATERIAL ROOM. "SEC. 4. There shall be provided within the de-naturing bonded warehouse a room to be designated as the de-naturing material room. This room is to be used alone for the storage of de-naturing materials prior to the de-naturing process. It must be perfectly secure, and must be so constructed as to render it impossible for anyone to enter during the absence of the officer in charge without the same being detected.