90 THE WONDERFUL CENTURY. CHAP. x. 



solid elements can be melted and many vaporized, lead- 

 ing to the conclusion that all matter can exist in the 

 three states solid, liquid, and gaseous, according to 

 the degree of heat to which it is exposed. 



The highly complex constitution of various organic 

 products albumin, fat, gums, resins, acids, oils, ethers, 

 etc. is the subject of organic chemistry, the study of 

 which has led to some of the most popularly interesting 

 discoveries. Coal-tar has furnished us with a wonderful 

 series of coloring matters, such as the aniline and other 

 dyes, while from the same material are produced benzol, 

 carbolic acid, naphtha, creosote, artificial quinine, and 

 saccharine, a substitute for sugar. The new explosives, 

 such as dynamite and nitro-glycerin, are produced from 

 animal or vegetable fatty matters; while some of the 

 greatest triumphs of the modern chemist are the artificial 

 production of natural substances, which were long sup- 

 posed to be due to organic processes alone. Such are 

 the dye indigo, citric acid, urea, and some others. 



The most recent great advance in the philosophy of 

 chemistry is exhibited in the views of the Russian 

 chemist, Mendeleef, as to the natural arrangement of 

 the elements, with certain deductions from it. The 

 whole of the best known elements form eight groups, 

 placed in vertical columns, depending on certain simi- 

 larities in their powers of chemical combination. These 

 are further arranged in twelve horizontal series, in which 

 the atomic weights are most nearly alike, while increas- 

 ing regularly from the first to the eighth group. In the 

 table thus formed there are certain gaps in the regular 

 order of increase of atomic weights, as if some elements 

 were wanting, while in other cases the place of an ele- 



