2co SCIENTIFIC APPARATUS. 



reduced to metals by heating with charcoal, a gas is evolved 

 which is identical with that produced by burning charcoal in 

 the air : in fact, the charcoal had combined with the prin- 

 ciple that had previously been abstracted from the air during 

 the process of calcination. The new antiphlogistic or Lavoisierian 

 chemistry met with many opponents, and it did not explain the 

 fact, that when metals are dissolved in sulphuric or muriatic acid, 

 a gas which was then supposed to be phlogiston is evolved. He 

 determined to try to discover what was produced by the com- 

 bustion of inflammable air, when he was informed that Cavendish 

 had found that the product was water. He repeated the experi- 

 ment on a larger scale, and found approximately that water is 

 formed by the combination of two volumes of inflammable air 

 with one volume of oxygen. He then showed that when steam 

 is passed over red-hot iron, the same inflammable air is produced, 

 and the iron becomes converted into a calx, which can afterwards 

 be reduced like other calces by means of the inflammable air, 

 water being again formed. The materials for a complete explana- 

 tion of known facts were then at hand. Hydrogen is evolved 

 from metals during solution in acids because water is decomposed, 

 a calx being formed which is dissolved by the acid ; and this 

 explanation has been accepted until comparatively recently, it 

 now being believed that the hydrogen is evolved by the decom- 

 position of the acid and not of the water. Lavoisier, noticing 

 that acids are formed when the products of the combustion of 

 carbon, sulphur, and phosphorus are dissolved in water, supposed 

 that oxygen is an essential constituent of all acids, and gave it the 

 name it now bears, signifying the acid producer. Subsequent 

 researches have shown that there are acids destitute of oxygen, 

 and that hydrogen is the element which is always present. The 

 chemical nomenclature was altered so as to accord with this 

 theory, and the system published in 1787 formed the foundation 

 of the one at present in use. 



About the same period analytical chemistry was making pro- 



