618 MANUAL OF NATURAL HISTORY. 



small compact masses, H. To, sp. gr. 37, 

 white ; 3, as Sulphuret or " Realgar," in 

 small granular masses, H. = 1*5 2, sp. gr. = 

 3 '7, red, also "Orpiment,"in lamellar masses, 

 H. = 1*5 2, sp. gr. 3 '4, lemon-yellow. Ar- 

 senical compounds before the blowpipe give 

 off a very peculiar odour resembling garlic. 

 Symb. As. 



8. FAMILY. Phosphorides. Minerals containing 



compounds of Phosphorus. Occurs combined 

 with metals forming " Phosphurets," or as 

 Phosphoric acid with metallic oxides forming 

 phosphates, as "Phosphate of Calcia," or 

 "Apatite/' also phosphates of magnesia, alu- 

 mina, iron, lead, copper, &c. Symb. P. 



9. FAMILY. Nitrogenides. Mineral substances 



containing nitrogen. Occurs 1, pure in the 

 waters of many springs, as at Bath, Chelten- 

 ham, &c., also given off from the soil in some 

 districts in the United States ; 2, combined 

 with oxygen as "Nitric acid," forming with 

 bases "Nitrates;" 3, mechanically mixed with 

 oxygen, forming atmospheric air, gaseous, 

 colourless, inodorous, sp. gr. ^-9722, other 

 characters principally negative. Symb. N. 



VII. ORDER. ANTHKAKEXIDES. 



Minerals containing elementary substances of the 

 carbon series. 



1. FAMILY. Anthrakides. Minerals composed of, 

 or containing, Carbon. Occur 1, pure as 1, 



