618 MANUAL OF NATUKAL HISTORY. 



small compact masses, H. 1*5, sp. gr. 3 7, 

 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. OKBEH. — Anthkakexides. 



Minerals containing elementary substances of the 

 carbon series. 



1. Family. — Anthrahides. Minerals composed of, 

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



