298 CARBON. 



nitric acid which has been described gives it without a trace of 

 sulphuric acid, when carefully conducted. 



Uses. Nitric acid is sometimes used in the fumigations re- 

 quired for contagious diseases, particularly in wards of hospi- 

 tals from which the patients are not removed, the fumes of this 

 acid being greatly less irritating than those of chlorine. For 

 the purpose of fumigation pounded nitre and concentrated sul- 

 phuric acid are used, being heated together in a cup. Nitric 

 acid is par excellence the solvent of metals, and has other most 

 numerous and varied applications not only in chemistry, but 

 likewise in the arts and manufactures. 



SECTION IV. 

 CARBON. 



Eg. 76.44 or 6.13; (75.6 or 6.05, Dr. Clark,) C; density of 

 vapour (hypothetical) 421.5. 



Carbon is found in great abundance in the mineral kingdom 

 united with other substances, as in coal of which it is the basis, 

 and in the acid of carbonates ; it is also the most considerable 

 element of the solid parts in both animals and vegetables. It 

 exists in nature or may be obtained by art, under a variety of 

 appearances, and possessed of very different physical proper- 

 ties. Carbon is a dimorphous body, occurring crystallized in 

 the diamond and graphite in wholly different forms, and when 

 artificially produced forming several amorphous varieties of 

 charcoal which are very unlike each other. 



Diamond. This valuable gem is found throughout the range of 

 the Ghauts in India, but chiefly at Golconda, in Borneo and 

 also in Brazil. It is always associated with transported mate- 

 rials, such as rolled gravel, and has never been found in situ, 

 so that its origin is doubtful, although it is now generally sup- 

 posed to have been produced by the slow decomposition of 

 vegetable matter. On removing the crust with which the crys- 

 tals are covered, they are exceedingly brilliant, refract light 

 powerfully, and are generally perfectly transparent, although 

 diamonds are sometimes black, blue and of a beautiful rose- 

 colour. The primitive form of diamond is the regular octohe- 

 dron, or two four- sided pyramids, of which the faces are equi- 

 lateral triangles, applied base to base. It is also often found in 



