128 M, Merzelius on I'litoric Acid. [Feb. 



•bluish green coloured regular six-sided prisms; but the liquid is 

 converted into a dry mass so soon after it begins to crystallize, 

 that, unless we operate upon large quantities, it is difficult to 

 obtain the salt in perfect crystals. A second crystallization 

 renders the salt paler coloured and more regularly formed. I 

 have remarked that all the coloured salts belonging to this class 

 have a deeper colour than usual when crystallized from a solu- 

 tion containing an excess of acid; but this difference in appear- 

 ance does not seem to be accompanied by a corresponding 

 difference in their composition. 



Si Heated Fluate of Oxide of Iron. — A semitransparent, pale 

 flesh coloured mass. It dissolves in water, and the solution is 

 faintly coloured. 



Silicaled Jiuate of oxide of cobalt and of oxide of nickel are 

 easily soluble in water, and crystallize in forms which are 

 exactly similar to those of the salts of manganese and iron. The 

 crystals are rhomboids, but pass into regular six-sided prisms, 

 whenever they are in a situation to elongate themselves. The 

 salt of cobalt is red ; that of nickel green. 



Silicated Jiuate of oxide of copper is easily soluble in water, 

 and shoots by spontaneous evaporation in transparent blue 

 coloured crystals, which are more determinately rhomboidal than 

 the preceding, but which have still a decided tendency to 

 become six-sided prisms. The crystals effloresce externally 

 and become opaque when exposed to the air, and their colour at 

 the same time changes to a light blue. 



The remarkable coincidence between the crystalline forms of 

 the greater number of the salts formed by the preceding isomor- 

 phous metallic oxides, led me to suspect that they might all 

 contain a similar number of atoms of water of crystallization. I 

 examined, therefore, the salts of oxidule of manganese and of 

 the oxides of zinc, cobalt, nickel, and copper, and found that 

 they all contain a quantity of water of crystallization whose oxy- 

 gen is seven times that of the base. The fatiscerated salt of 

 oxide of copper still retains a quantity of water whose oxygen is 

 five times that of the oxide of copper. 



Silicated Jiuate of oxidule of copper has a red colour, and 

 closely resembles the corresponding simple fluate both in exter- 

 nal appearance, and in the decomposition which it sustains 

 through the combined action of air and moisture. In a high 

 temperature it melts, and loses its fluate of silica. 



Silicated Fluate of Oxide of Lead. — A transparent gummy- 

 looking mass, soluble in water, and possessing the peculiar 

 taste of the salts of lead. 



Silicated f note of oxide of cadmium is extremely soluble in 

 water, and crystallizes in long colourless prisms, which contain 

 •water of crystallization. 



Silicated Jiuate of oxidule (f tin, like the preceding, is very 



