424 Berzelius on a new Mineral Body, [Dec. 



and the muriatic acid dissolves the peroxide of iron with a 

 portion of the selenic acid not decomposed. This is the reason 

 why the muriatic solution assumes a yellow colour. 



The biseleniate is obtained when the preceding salt is dissolved 

 in selenic acid, or when we mix aprotosalt of iron with a soluble 

 biseleniate. The biseleniate of iron is but little soluble, and 

 begins very speedily to be decomposed. If we heat a solution 

 containing this biseleniate, it is decomposed, and yields a brown 

 precipitate. It is a mixture of perseleniate and reduced 

 selenium. 



18. Perseleniate of Iron. — The neutral salt precipitates by 

 double decomposition : a white powder falls, which becomes a 

 little yellowish on drying. The perseleniate when heated gives 

 out. first its water of combination, and becomes red. At a 

 higher temperature the acid sublimes, and may be entirely 

 driven off. 



If we dissolve iron in a boiling hot mixture of selenic acid 

 and nitromuriatic acid, taking care that all the nitric acid is not 

 decomposed, the liquid deposits during its cooling on the sides 

 of the vessel a pistachio green salt in leaf-form crystals. I have 

 reasons for considering it as a biperseleniate of iron. It does 

 not dissolve in water, but muriatic acid dissolves it, and assumes 

 an orange colour. Caustic potash added in excess gives a red 

 precipitate ; from which it follows that the green colour is not 

 owing to the presence of protoxide of iron. When this salt is 

 exposed to a high temperature, it gives out its water of crystal- 

 lization, and appears black, but becomes colcothar-red on 

 cooling. When the temperature is increased, selenic acid is 

 disengaged without any trace of reduced selenium, which would 

 not have been the case if it had contained protoxide of iron. 

 Nothing remains ultimately but red oxide of iron. 



If we digest either of the above-described seleniates with 

 caustic ammonia, that alkali separates a portion of the selenic 

 acid, and there remains a red subperseleniate, which, like the 

 Other subsalts of peroxide of iron, passes through the filter when 

 we attempt to wash it. This subsalt is decomposed by heat, 

 and leaves pure peroxide. From an analytical experiment to 

 which, however, I do not attach much confidence, this subsalt 

 is composed of 



Acid 52 



Peroxide 48 



100 



and the acid and base contain equal weights of oxygen. 



19. Seleniate of Cobalt. — The neutral salt is a rose-coloured 

 insoluble powder. The biseleniate gives, when evaporated, a 

 beautiful shining-red varnish. 



20. Seleniate of Nickel. — The neutral salt while still moist is 



