236 Scientific tJotices — Mineralogy, [MahCh^ 



What is called molybdous acid, that is to say, the blue oxide 

 of molybdsena, is not a particular acid. It cannot be combined 

 with alkalies, which, on the contrary, decompose it, by pre- 

 cipitating the hydrate of the yellow oxide, and combining with 

 the molybdic acid. It may be produced most readily in dis- 

 solving the bimolybdate of ammonia, and adding to it a solution 

 of a salt with a base of the deutoxide. It produces a precipitate 

 of a fine deep blue, which is very soluble in water, and is only 

 deposited because the water contains salts. We may wash it 

 with a solution of sal ammoniac, afterwards removing the salt by 

 a little cold water. It gives with warm water a blue solution, 

 highly saturated, which may be easily preserved at the ordinary 

 temperature of the atmosphere. In the dry form it resembles 

 indigo, and retains its solubility in water. 



Prof. Berzelius has found, that the deutoxide of molybdsena is 

 composed of one atom of molybdsena and two atoms of oxygen. 

 The molybdic acid contains three atoms. The blue oxide is a by- 



toolybdate of the deutoxide of molybdsena, that is. Mo. + 4 Mo. 

 There is still another combination between the oxide and the acid 

 which is produced when the blue liquid is digested with metallic 

 molybdsena. It is green, equally soluble in water, and precipitable 

 irt sal ammoniac. M. Berzelius supposes its composition to be 



Mo. + 2 Mo. Tungstic acid likewise combines with the deu- 

 toxide of molybdsena, and the combination is very soluble in 

 water, and of a superb purple colour. It is also precipitated by 

 sal ammoniac. 



The molybdic acid performs the part of a base towards the 

 stronger acids. M. Berzelius has examined them in this point 

 of view, and has described some of the salts which it forms. 



M. Berzelius has discovered a new sulphuret of molybdsena, 

 proportional to the molybdic acid. It is of a ruby colour, trans- 

 parent, and crystallized. It combines with the metallic proto- 

 sulphurets, and forms with them particular salts, of which a 

 great number are soluble in water. 



Molybdsena combines with chlorine in three proportions. The 

 first is red, and a little volatile. The second is black, «rery 

 fusible, very volatile, and crystallizes in a black mass, of a 

 brilliant colour, like iodine, which it resembles even in the 

 colour of its gas, which, however, is more red than violet. The 

 third is colourless, and crystallizes in scales. These three 

 chlorides correspond to the muriates of the protoxide, of the 

 deutoxide, and of the peroxide, that is to say, of the acid. 

 Iodine does not combine in the dry way with molybdsena, but 

 the hydriodic acid dissolves the protoxide and the deutoxide. 

 The molybdic acid decomposes it, and separates the iodine 

 from it. 



