A CENTURY OF CHEMISTRY. 79 



do when the barrel of gunpowder explodes, but the 

 total amount of matter is the same in the end as it 

 was in the beginning. 



The doctrine of the Conservation of Matter states, 

 as Ostwald puts it, that ^ the total mass of the sub- 

 stances taking part in any chemical process remains 

 constant." And since masses of bodies are at any one 

 place proportional to theii* weights, the doctrine 

 may read that in any chemical process the weight 

 remains constant. If we change the contents of a 

 sealed vessel by heating, or by mixtures brought about 

 through shaking, or otherwise, we find that the 

 weight at the end equals the weight at the begin- 

 ning.* 



Although the recognition of the conservation of 

 matter was brought about by the work of many, 

 it may be particularly associated with Lavoisier. 

 For one of his earliest investigations, on the sup- 

 posed conversion of water into earth, he constructed 

 what was at the time the most accurate balance in 

 existence, and he reaped the usual reward of the 

 accurate measurer. When he passed water vapour 

 over red-hot iron turnings and collected the resulting 

 hydrogen, he weighed everything — the water, the iron 

 before and after, and the hydrogen. It was by 

 such typical experiments that " with the balance in 

 his hand, he vindicated the universality of the prin- 

 ciple of the conservation of matter." f 



The establishment of the general fact of the con- 

 servation of matter was of much more than theoreti- 

 cal interest; it was not only a foundation-stone, hut a 



*W. Ostwald, Outlines of General Chemistry, trans, by 

 James Walker, 1890, Chap. I. 



t A. Ladenburg, History of Chemistry, trans, by L. Dob- 

 bin, 1900, p. 21. 



