1819.] extracted from Pyrites at Fahlun. 423 



crystallization, and then melts. The fused mass is yellow and 

 transparent; but on cooling, it becomes white. Its fracture is 

 crystalline. When exposed to nearly a white heat, it boils, and 

 a part of the acid is disengaged. At last the mass becomes 

 solid. It is then in the state of a subseleniate of zinc no longer 

 altered by heat. 



The biseleniate is very soluble in water. Its solution when 

 evaporated gives a transparent mass, full of small rents, and 

 similar to gum. 



1 3. Seleniate of Manganese. — The neutral salt is a white inso- 

 luble powder, which, when dried, forms a soft meal, like the 

 seleniate and carbonate of lime. It is very fusible, but preserves 

 its acid well in close vessels ; but if the air have free access, the 

 manganese unites with more oxygen, and the selenic acid is 

 disengaged. The seleniate of manganese in a state of fusion 

 possesses the property of destroying glass in a much higher 

 degree than the seleniates of lime and magnesia. The bubbles 

 which form in the glass are larger, they come to the surface, and 

 opening, leave holes. The interstices between these holes are 

 not liquefied, and the glass thus decomposed is not at all coloured 

 by the oxide of manganese. 



The biseleniate is very soluble. When evaporated, it gives a 

 crystallizable saline mass. A high temperature reduces it to the 

 neutral state. 



14. Perseleniate of Uranium. — The neutral salt is a lemon- 

 yellow powder, which, when heated, gives out its salt and a 

 portion of oxygen, leaving green oxide. Biperseleniate is formed 

 by the solution of the preceding salt in selenic acid. By evapo- 

 ration, a varnish of a pale-yellow colour, and transparent, is 

 obtained. When entirely dry, it is white, opaque, and crys- 

 talline. 



15. Perseleniate of Cerium. — Both the neutral salt and the 

 biperseleniate resemble exactly the same salts of the peroxide 

 of uranium. 



16. Protoseleniate of Cerium. — A white insoluble powder, 

 which dissolves in selenic acid, and forms a soluble biseleniate. 

 This is one of the few properties by which the protoxide of 

 cerium differs from yttria. 



17. Protoseleniate of Iron. — Selenic acid hardly attacks iron. 

 The metal assumes a copper colour, being covered by a thin 

 coating of selenium, and this puts an end to all action. 



If we mix a protosalt of iron with a neutral alkaline seleniate, 

 a white precipitate falls, which gradually assumes a grey colour, 

 and then a yellow, in proportion as the air acts upon it. After 

 being separated, washed, and dried, it is yellowish-white. If 

 we pour muriatic acid on seleniate of iron newly formed, and 

 especially if we apply a little heat, the acid is decomposed, leav- 

 ing selenium reduced, and not dissolved. By the action of the 

 acid, the protoxide of iron reduces a part of the selenic acid, 



