BORON. 309 



volume of chlorine under the influence of the sun's rays, and 

 forms phosgene gas or chlorocarbonic acid. It is also absorbed 

 by potassium gently heated, and that metal is employed to sepa- 

 rate carbonic oxide from a mixture of hydrogen and gaseous 

 hydrocarbarets, as in the analysis of coal gas. But carbonic 

 oxide is supposed to exist in a greater number of compounds, 

 and to be the radical of a series, of which the following sub- 

 stances are imagined to be members : 



CARBONIC OXIDE SERIES. 



Carbonic oxide. .... CO 



Carbonic acid. .... CO + O 



Chlorocarbonic acid. . . . CO-fCl 



Oxalic acid ...... 2CO + O 



Oxamide ...... 2CO + NH 2 



Oxicarburet of potassium. . . 7CO+3K 



Croconic acid. . . . . 5CO + H 



Mellitic acid. .... 4CO + H 



In these compounds carbonic oxide is represented as playing 

 the part of a simple substance, and forming a variety of pro- 

 ducts by uniting with oxygen, chlorine, hydrogen and other 

 elements. 



Oxalic, mellitic and croconic acids are sometimes enumerated 

 as oxides of carbon, along with carbonic acid and carbonic oxide, 

 but as the former bodies always exist in a state of combination 

 and cannot be isolated, they have not an equal claim to the 

 same early consideration as the latter compounds. 



SECTION V. 

 BORON. 



Eg. 136.25, or 10.91 ; B; density of vapour (hypothetical) 

 751; 



Boron is an element having some analogy to carbon, but 

 sparingly diffused in nature. It is never found, except in com- 

 bination with oxygen as boracic acid, of which the salt of soda 

 has long been brought to Europe from India in a crude state, 

 under the name of tinkal and termed borax when purified. The 

 impure borax or tinkal forms a saline incrustation in the beds of 

 certain small lakes in an upper province of Thibet, which dry up 



