HYDROCHLORIC ACID TYPE. 7 



ship, constitutes the great chemical advance of the last dozen 

 years or so ; and, at the present time, a proper understanding of 

 these types enables us to give at once a more or less satisfactory 

 interpretation of even the most recondite discoveries of modern 

 organic chemistry. 



(6.) I need scarcely remind you that among the infinite 

 number of bodies known to chemists, some of them, so far as 

 our present knowledge goes, appear to consist of one kind of 

 matter only. For instance, while cinnabar may be proved to consist 

 of two different kinds of matter, known as sulphur and mercury 

 respectively, out of mercury we can obtain nothing but mercury, 

 and out of sulphur nothing but sulphur. Bodies of this de- 

 scription, therefore, which the chemist has not succeeded in re- 

 solving into two or more different kinds of matter, are assumed 

 to consist of one kind of matter only, and are accordingly termed 

 simple bodies or elements. These elements amount to about sixty 

 in number, and are possessed of very diverse properties. About 

 four-fifths of them are metallic, as mercury, and silver, and gold, 

 and copper, and lead, and iron. The remainder are non-metallic, 

 as oxygen, and chlorine, and bromine, and sulphur, and phos- 

 phorus, and charcoal. The great majority of them exist natu- 

 rally in the solid state. Only two are liquid, namely, bromine 

 and mercury ; while four of them are gaseous, namely, hydrogen, 

 chlorine, oxygen, and nitrogen. Now it is the combinations of 

 these four gaseous elements with one another, or rathtr, I should 

 say, the combinations of hydrogen with the other three gaseous 

 elements, which constitute our primary chemical types chloride 

 of hydrogen or hydrochloric acid, oxide of hydrogen or water, 

 and nitride of hydrogen or ammonia which we will now con- 

 sider seriatim. 



(7.) If we expose a mixture of chlorine and hydrogen gases to 

 diffused daylight, they gradually combine with each other to pro- 

 duce a compound gas called hydrochloric acid the gas which 

 is contained in this sealed tube, and which I dare say I shall 

 be able to render evident to you by breaking off the point of 

 tube under water. The existence of hydrochloric acid gas within 



