[43] Die Lehre von den chem. Fermenten. Heidelberg, 1882. [44] Quoted from Gamgee’s Physiological Chemistry of the Animal Body, vol. 2, p. 7. [45] Chittenden and Meara. A study of the primary products resulting from the action of superheated water on coagulated egg-albumin. Journal of Physiol., vol. 15, p. 501. We can find many illustrations among chemical phenomena where one body, even though present in small quantity, acts as a go-between and makes possible an almost indefinite exchange of matter and energy. Take as an illustration, the part played by water in determining the explosion of oxygen and carbon-monoxide gas. Some years ago, Dixon[46] called attention to the fact that a mixture of these two gases when perfectly dry would not explode even by contact with red hot platinum wire. The presence, however, of a small amount of aqueous vapor would at once cause an explosion to occur. In confirmation of this observation, Traube[47] has reported that a flame of carbon-monoxide gas introduced into a perfectly dry atmosphere is at once extinguished. In a moist atmosphere, on the other hand, the flame will continue to burn indefinitely, that is as long as the CO gas is supplied. In these cases, the water, which is so necessary for the appearance of the reaction, and which furnishes a striking illustration of the action of a contact or catalytic substance is not purely passive. To be sure, only a minimal amount is necessary for the combustion of an indefinite amount of carbonic oxide, but the water enters into the reaction itself. It is to be noticed that carbonic oxide and water alone, even at high temperatures, will not react, but in the presence of oxygen the water is decomposed with formation of hydrogen-peroxide, thus: CO + 2 H_{2}O + O_{2} = CO(OH)_{2} + H_{2}O_{2}. [46] Chemical News, vol. 46, p. 151. [47] Bericht. d. Deutsch. chem. Gesellsch., Band 18, p. 1890. The hydrogen-peroxide thus formed combines with carbonic oxide to form carbonic acid, which in turn is decomposed into the anhydride CO_{2}, with regeneration of water, the latter being available for further action of the same order: H_{2}O_{2} + CO = CO(OH)_{2} 2 CO(OH)_{2} = 2 CO_{2} + 2 H_{2}O.