258 Chemical Powers of Ammoniacal Salts. 



over the flame of a spirit lamp, and in contact with the pulverised 

 mineral ; nitrate of ammonia, in powder, is then to be added from 

 time to time, until the solution is effected. In most cases, the nitre 

 may be omitted with advantage, as it is impossible to remove any ex- 

 cess by heat. 



The following experiment is very indicative of intense chemical ac- 

 tion. 



When the nitro-rauriafe (composed of equal parts) is fused be- 

 tween two watch glasses, the under glass becomes corroded near- 

 ly to one half of its thickness and the effect even extends to the 

 cover. The heat of a spirit lamp is quite sufficient for this purpose. 

 Here, without water or even perfect fusion, the alkali is entirely re- 

 moved and the silex left, forming a snow-white, opaque surface, so 

 soft as to admit of being cut through with the point of a needle or 

 knife ; green glass is not so easily affected, owing to its greater hard- 

 ness and the absence of lead. The fused nitrate alone, if confined 

 between watch glasses, also produces slight corrosion, but the effect 

 is so remarkable when the nitro-muriate is employed, that a per- 

 son, operating upon an unknown mineral and ignorant of this prop- 

 erty, would be induced to attribute the result to the presence of flu- 

 oric acid. Indeed, vi^hen we consider that the effect appears to de- 

 pend upon the liberation of nitro-muriatic acid or, perhaps, even to 

 highly concentrated nitric acid alone, it does not seem improbable 

 that similar cases have often occurred by the common modes of 

 analysing, and this opinion is further strengthened by the fact that 

 some minerals, as the chondrodite, appear to have furnished fluoric 

 acid to one operation and not to another. 



Fused nitrate of ammonia alone has some very peculiar proper- 

 ties, which may here be noticed. In the following experiments it 

 operates with the energy of nitric acid itself. 



It instantly attacks crystallized ferrocyanate of potassa, liberating 

 the acid and then rapidly effecting its decomposition, so that nothing 

 remains but the iron, of the ferrocyanic acid, in the state of peroxide. 



Chromate or bi-chromate of potassa undergoes decomposition so 

 suddenly as to produce an explosive effect. If a little water be mix- 

 ed with these salts and heat applied, chromic acid is merely libera- 

 ted and imparts its fine ruby red. color to the mass, but, without this 

 fluid, the mineral acid is immediately converted into the brown or deu- 

 toxide. 



Hydriodate of potassa also suffers instantaneous decomposition ; 

 it becomes brown and free iodine escapes abundantly. 



