Drebbel built a submarine which was manned by 12 oarsmen, made of wood and waterproofed by a coat of greases leather. It successfully traveled along the River Thames from Westminster to Greenwich, at a dept of 15 ft. The trip, and the method used to keep the oarsmen alive, was subsequently verified by Robert Boyle . Occurrence Oxygen occurs in the free state as a gas, to the extent of 21 per cent by volume or 23 per cent by weight in the atmosphere. Combined Oxygen also occurs in water, in vegetable and animal tissues, in nearly all rocks and in many minerals.
Oxygen occurs to a larger extent in the earth's crust than any other element.
Extraction Preparation Because oxygen is a component of air, it has been studies extensively over the centuries and there is a large number of different methods for its preparation. The most convenient method for preparing oxygen in the laboratory involves either the catalytic decomposition of solid potassium chlorate or the catalytic decomposition of hydrogen peroxide. Preparation of oxygen Using potassium chlorate Potassium chlorate decomposes at a low temperature if previously mixed with manganese dioxide which is a catalyst for the decomposition. The decomposition of hydrogen peroxide using manganese dioxide as a catalyst also results in the production of oxygen gas. The electrolysis of acidified water is carried out in a Hofmann Voltameter .