622 TELLURIUM. 



as a mineral. Chromate of lead is dimorphous, and corresponds 

 in the least usual of its forms with molybdate of lead : hence 

 molybdenum is connected with the magnesian metals, and 

 tungsten also with the same class, from the isomorphism of the 

 tungstates and molybdates. 



Sulphurets of molybdenum. The bisulphuret is the ore from 

 which the compounds of this metal are derived. It occurs in 

 many parts of Sweden, and might be procured in quantity if 

 any useful application of the metal were discovered. It is a 

 lead-grey mineral, having the metallic lustre, composed of flexible 

 laminae, soft to the touch, and making a streak upon paper, like 

 plumbago. Nitric acid oxidates it easily, without dissolving it. 

 Its density is from 4.138 to 4.569. A tersulphuret of molybde- 

 num is obtained in the same way as the corresponding com- 

 pound of tungsten, and affords crystallizable sulphur salts > 

 which are red. The sulphomolybdate of sulphuret of potassium 

 combines likewise with nitrate of potash. When a solution of 

 the former salt is boiled with tersulphuret of molybdenum in 

 excess, the latter is converted into bisulphuret of molybdenum, 

 and a quadri sulphuret of molybdenum dissolves in combination 

 with the sulphuret of potassium. The quadrisulphuret may be 

 precipitated by hydrochloric acid, and when dried is a cinnamon 

 brown powder. 



Chlorides of molybdenum. A protochloride is formed when 

 molybdous oxide is dissolved in hydrochloric acid ; the bichlo- 

 ride when molybdenum is heated in dry chlorine gas, as a dark- 

 red gas, which condenses in crystals, like those of iodine. It 

 forms a crystallizable double salt with sal ammoniac. The 

 chloromolybdic acid, or compound of terchloride of molybdenum 

 and molybdic acid, MoO 2 Cl or MoCl 3 + 2MoO 3 , is formed with 

 molybdic acid, when molybdic oxide is exposed to chlorine gas 

 at a red heat. It sublimes under a red heat, and condenses 

 in crystalline scales, which are white with a shade of yellow. 



SECTION VI. 

 TELLURIUM. 



Eq. 801.8 or 64.25; Te. 



Tellurium is a metal of rare occurrence, and appeared at one 

 time to be almost confined to certain gold mines in Transyl- 



