Clarke and Steiger — Action of Ammonium Chloride. 35 



rado, originally described by Koenig as arfvedsonite, but 

 identified by Lacroix as near riebeckite, happened to be avail- 

 able. It was treated with ammonium chloride in the usual 

 way, and no presence of liberated gas was noticed when the 

 tube was opened. On leaching the product with water, fer- 

 rous chloride went into solution, and ferric hydroxide with 

 some manganic hydroxide were deposited. In the leached 

 mass 6*90 per cent of soluble silica was found, and in the 

 wash water from the leaching there were 6*76 per cent of soda. 

 According to Koenig's analysis the mineral contains 8*33 per 

 cent of soda, so that a large portion of the total amount had 

 been extracted. There was also, evidently, a considerable 

 breaking down of the molecule, but no definite ammonium 

 derivative had been formed. This is shown by the following 

 analysis of the leached residue, which is contrasted with 

 Koenig's published analysis* of the original mineral, in order 

 to indicate the amount of change. In the third column of 

 figures we give the amount of each constituent which could be 

 dissolved out from the residue by treatment with hydrochloric 

 acid. 



Riebeckite (Koenig). Residue (Steiger). Soluble portion. 



Si0 2 49-83 67-54 



Ti0 2 __. 1-43 



Zr0 2 -75 



Fe 2 3 14-87 21-28 15-74 



FeO . 18-86 4-94 4'94 



MnO _. 1-75 -64 *64 



MgO -41 " none 



CaO trace 



Na 2 8-33 ) 



K 2 6 1-44 \ 104 



NH. -53 -53 



H 2 ._. -20 (ign.) 3-33 



CI . trace 



97-87 99-30 



The residue is evidently a mixture of free silica and ferric 

 hydrate with probably at least two silicates, one soluble, the 

 other insoluble in hydrochloric acid. The reaction itself is 

 noteworthy because of the fact that the original mineral is but 

 slightly attacked when boiled with strong hydrochloric acid. 

 The other minerals so far studied by us are all easily decom- 

 posable by acids, while this one is quite refractory. The 

 energetic character of the ammonium chloride reaction is thus 

 strongly emphasized. 



* Dana's System of Mineralogy, 6th ed., p. 400. 



