Oxides of Vanadium and Uranium. 143 



is partially soluble in hydrochloric acid, with evolution of a 

 gas, doubtless hydrogen. 



The following determinations were made with the prepara- 

 tions marked " A, " containing 90*0 per cent of vanadium and 

 8"5 per cent of oxygen. 



Experiment 1. — "A" 1-000, sulphur 1*000, sodium peroxide 

 15 grams. Heat effect 9003 c . Deducting 5270° for sulphur 

 and 30° for iron burned, and 71° for oxygen absorbed, leaves 

 3632 c for the heat effect of 1 gram of impure vanadium react- 

 ing with sodium peroxide. 



Experiment 2 . — Made as Exp. 1, only 1*200 gram of "A" 

 was taken. Result for 1 gram, 3721 c . 



The combustions were apparently complete since the fusions 

 left no unburned particles when dissolved in water. Tbe mean 

 of the results is 3677°. This number divided by 0*9, the 

 amount of vanadium in 1 gram, gives 4086° and for the heat 

 of reaction of 102 grams of vanadium, two gram atoms, with 

 sodium peroxide 416,800°. From this number is derived 

 2V+50=V 2 O 6 + 348,000°. If correction be made for the 

 oxygen in the metal used, taking the heat effect of one atom as 

 145,000 c , the result is 422,000°. Preparation " B " in one ex- 

 periment, making the same correction, gave 460,000°. The 

 average of the last two is 441,000°. 



Roscoe* states that vanadium monoxide, V 2 0, is formed by 

 the prolonged exposure of finely divided vanadium to the air, 

 but says nothing of its properties except that it is a brown 

 powder. He also states that vanadium is not attacked by 

 hydrochloric acid. The writer has found that all of the pre- 

 parations made by reducing an oxide with magnesium set free 

 hydrogen when treated with hydrochloric acid, yield a green 

 solution and leave a grey residue which does not dissolve on 

 long heating to 100° in concentrated acid in a sealed tube. 

 The evolution of hydrogen is apparently not due to the action 

 of metallic vanadium on the acid but to the monoxide or 

 dioxide reacting to form Y 2 C1 2 (unknown) or YC1 2 , either of 

 which would set free hydrogen from hydrochloric acid. 

 Roscoe statesf that when hydrochloric acid is added to a violet 

 solution of vanadium dichloride hydrogen is evolved and the 

 trichloride is formed. 



Vanadium Pentoxide. 



Vanadium pentoxide was made in the usual way by heating 

 ammonium vanadate. Thus prepared it is commonly regarded 

 as amorphous but under the microscope it appears to be 

 crystalline. It may be that the form of the crystals of 

 ammonium vanadate is not changed on heating and that the 



* A Treatise on Chemistry, Roscoe & Schorletnmer, 4th ed., ii, 902. 

 flbid., p. 909. 



