MANUAL OF NATURAL HISTORY. 615 



bases. Titanic acid if fused with an alkali 

 is soluble in dilute hydrochloric acid, in 

 which a solution of gall-nuts causes an orange 

 red colour. Symb. Ti 



8. FAMILY. Tungstenides. Minerals containing 

 principally compounds of Tungsten. Oc- 

 cur 1, as Oxide or "Tungstie acid," with 

 iron and manganese as " Wolfram/' trimetric, 

 H. = 5, sp. gr. = 7'3, dark brown ; 2, with 

 calcia (lime) as " Scheelite," in square octa- 

 hedrons, H. = 4-5, sp. gr. = 6, white. Wolfram 

 readily fuses before the blowpipe into a mag- 

 netic globule studded with crystalline points. 

 Symb. W. 



9. FAMILY. Molybdenides. Minerals principally 

 composed of compounds of Molybdenum. 

 Occur 1, as Oxide or " Molybdic-ochre," an 

 earthy yellow powder, yielding a yellow glass 

 with Microcosmic salt ; 2, as Molybdic-acid 

 with lead or " Wulfenite," in square octo- 

 hedrons, or very short prisms, H. = 2 -8, sp. 

 gr. = 6'5, yellow; 3, as bisulphuret or 

 " Molybdena," hexagonal, H. = 1 1*5, sp. 

 gr. = 4-5, feel unctuous, lustre metallic, 

 lead-gray. Symb. Mo. 



VI. ORDER. IRIDEXIDES. 



Minerals containing metals of the Iridium series. 

 1. FAMILY. Iridiides. Minerals containing Iri- 

 dium. Occur 1, alloyed with Osmium as 

 " Iridosmine," H. = 6-7, sp. gr. = 19-21, 



