376 HISTORY OF SCIENCE. 



359 grains of oxide of iron, precisely like that produced by the com- 

 bustion of iron in oxygen gas ; and 100 grains of water had disappeared 

 from the retort I, etc. Thus 100 grains of water had been decomposed 

 into 85 grains of oxygen and 15 grains of an inflammable gas, for which 

 principle as it exists in water Lavoisier proposed the name hydrogen 

 (Greek, Map, water ; -ye?, produce) ; while hydrogen gas is the name to 

 be given to what he terms " its combination with caloric." It may be 

 mentioned that the relative proportions of oxygen and hydrogen in 

 water, as found by Lavoisier in this and other experiments, are erro- 

 neous by excess of hydrogen, the true proportions being eight parts 

 of oxygen to one of hydrogen. 



Lavoisier conducted the reverse or synthetical experiment so as 

 clearly enough to prove the production of water from the combination 

 of hydrogen and oxygen only; but the opposition and discussion 

 which arose on this experiment were not finally set at rest until La- 

 voisier's disciples, Fourcroy, Seguin, and Vauquelin repeated the ex- 

 periment in 1790 on a larger scale, by means of the apparatus shown 

 in Fig. 117, which had been used by Lavoisier. The oxygen gas 

 was contained in the gas-holder B; the hydrogen, in bulk double 

 the oxygen, filled the vessel B'. A is a strong glass globe which was 

 exhausted of the air at the commencement by means of the tube G. 

 The hydrogen was burnt at a jet (not shown in the figure) near a b, 

 which are metallic conductors arranged so that an electric spark might 

 be passed between them in order to inflame the hydrogen in the first 

 instance, c c are tubes for indicating the pressures of the gases, in 

 order that they may be kept equal, while the flow of gas is so regulated 

 that twice as much hydrogen as oxygen passes into the globe. In 

 this way it became possible to maintain the combustion of hydrogen 

 indefinitely ; and, in fact, the experiment was carried on for six days 

 continuously, day and night, from the i3th to the 22nd of May, 1790, 

 each of the three experimenters taking his turn. More than half a 

 pint of pure water was produced in the experiment, and when this was 

 withdrawn from the glass, there was of course no difficulty in proving 

 that the liquid was water and. nothing but water. Some of the identical 

 liquid is still preserved in the laboratory of the Museum of Natural His- 

 tory at Paris ; and a large part of the apparatus employed by Lavoisier 

 and others in experiments like these, memorable in the history of 

 science, may also yet be seen at the Conservatoire des Arts et Metiers. 



Lavoisier's great work in chemistry consisted in the overthrowing of 

 the erroneous phlogistic theory, and in the giving to the world true 

 ideas of combustion, of the constitution of the atmosphere, of the com- 

 bination of elements to form acids and bases, and of the union of these 

 to produce salts. In his memorable researches Lavoisier appeals to 

 the balance, as when he argues that the products of combustion being 

 heavier than the combustible body, the former cannot be the elements 

 of the latter. He also distinguishes degrees of oxidation, and often 



