264 Berzehus on a new Mineral Boch/, 8fC. [Oct. 



we make the same experiment with an earthy seleniate, the 

 selenium is disengaged in proportion as it is deoxidated. The 

 metallic seleniates are reduced by the action of charcoal into 

 seleniurets, and the selenium remains combined with the metal. 

 Selenic acid does not communicate to the seleniates any 

 peculiar taste. The alkaline seleniates have a weak saline taste, 

 while the earthy and metalline seleniates have the taste peculiar 

 to the base, just as happens in their combinations with other 

 acids. 



1. Seleniate of Pol ash. — The neutral salt is soluble in water in 

 almost every proportion. When the liquid is evaporated, it 

 becomes covered with a saline pellicle, composed of small crys- 

 talline grains, the form of which I have not been able to deter- 

 mine. These grains are likewise deposited at the bottom. The 

 salt does not crystallize on cooling, but requires a constant 

 evaporation. When evaporated to dryness, it leaves a rough 

 mass, which attracts moisture from the atmosphere. When 

 heated to redness, it melts, and becomes yellow. On cooling, 

 it recovers its white colour. It is insoluble in alcohol. 



The biseleuiale crystallizes, though with difficulty, when its 

 solution has been concentrated to the consistence of a syrup, and 

 then allowed to cool. The salt is deposited in feather-shaped 

 crystals,, which at last fill the whole matter which appears 

 entirely solidified. This salt is deliquescent. Alcohol dissolves it 

 in small quantity. * It is decomposed by heat, letting go the 

 half of its acid ; though the fire must be continued a long time 

 to obtain a complete decomposition. 



The quadriseteiiiate does not crystallize, and when evaporated 

 to dryness, becomes liquid again in a short time by absorbing 

 moisture from the air. 



2. Seleniate of Soda. — The neutral salt is very soluble in 

 water. It has the taste of borax. If we continue the evapora- 

 tion after reducing it to the consistence of a syrup, the solution 

 begins to deposit small crystalline grains, and it becomes covered 

 with a saline pellicle, of a white enamel colour. It does not 

 crystallize by cooling. When evaporated to dryness, it does not 

 absorb moisture from the atmosphere. Alcohol does not 

 absorb it. 



The biseleniate crystallizes, if a solution concentrated to the 

 consistenee of a syrup be allowed to cool slowly. The crystals 

 are acicular, partly grouped in stars, and partly in grains com- 

 posed of concentric rays. It does not effloresce ; but, when 

 heated, it loses its water of crystallization, and then melts and 

 forms a yellow liquid matter. On cooling, it becomes white and 

 crystalline, and acquires a radiated fracture. When heated to 

 redness, the selenic acid evaporates in the form of a white smoke, 

 and neutral seleniate remains. 



The qiiadriseleniate crystallizes in needles when evaporated 

 spontaneously. It is not altered by exposure to the air. 



