426 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Carbon, Boron, and Silicon. 



They are denoted by a pyramid in the center of the first dia- 

 gram (fig. 1).* The three boundaries of one face of a pyramid 

 will respectively represent these three elements. 



Silicon or Siliciumfuses at about 1450 degrees Centigrade — the 

 melting point of steel. Boroii is reduced only at a still higher 

 heat. Carbon when perfectly isolated and surrounded by sub- 

 stances with which it has no affinity, remains solid and infusible 

 under the highest heat thus far applied. 



As the antipodes of these hai'd elements we have three gases 

 which under the lowest temperature and highest pressure yet ap- 

 plied to them, have not been reduced to the solid or even to the 

 liquid state. 



They are oxygen, nitrogen, and hydrogen. 



The three lines in figure 1, fartherest from the centre, represent 

 these attenuated elements. To the class of gases also belong 

 ■fluorine and chlorine, which are represented by the lower lines in 

 fio-ure 2. Thus the five gases are designated by the five boundary 

 lines of that diagram. Fluorine is the only element which has 

 not been obtained in a separate state; but considerations which 

 need not here be given, justify the assumption that fluorine, when 

 isolated, is a colorless gas. 



Chlorine is a transparent greenish-yellow gas at ordinary tem- 

 peratures. When subjected to a pressure of about sixtj' pounds 

 to the square inch, it becomes a yellow liquid; yet when cooled 

 to 140 deo^rees Centigrade it still remains unfrozen. 



Between the three hard elements and the five gases, are found 

 five non-metallic elements, which readily pass from the solid to 

 the o-aseous state on being heated, viz., bromine, iodine, sulphur, 

 selenium and phosphorus. If the French view is adopted we must 

 include as metalloids, arsenic and tellurium. These seven elements 

 are shown in fio-ure 3, which is so arranged as to represent the 

 solid state of the element b}' a thick line nearest the center ; then 

 the liquid, and lastly the gaseous state near the outside of the 

 diagram. It will be observed that bromine is not represented by 

 a thick line because at ordinary temperature it is a liquid. Bro- 

 mine becomes a solid at 12°5C. and boils at 63°C. 



*The fio-nros and symbols illustrating this article have be«n entered according to Act of 

 Congresg,°in the year 1867, by S. D. Tillman, in the Clerk's office of the District Court 

 of the United States for the Southern District of New York. 



