25S Mr. J. D. Smith on the supposed }ic-:jd Metal Donimn. 



Arseniate of potash when added to A. gave a white flocky 

 precipitate" ; to B. slight white, which on the addition of a 

 drop of ammonia became a dense white pi'ecipitate ; with C. it 

 acted in the same manner as with B. 



Chromate of potash gave with A. a "copious yellow preci- 

 pitate ;" with B. and C. a gelatinous yellow precipitate. 

 Sulphate of soda : A. gave none, B. and C. none. 

 Tartrate of potash with A. produced a " slight white preci- 

 pitate" ; with B. the merest trace of a precipitate, and the 

 same with C. 



Tincture of galls gave no precipitate with A., but deve- 

 loped in B. a bluish black tint, and the same, only not so deep, 

 in C. 



Ferrocyanate of potash is not mentioned as having been 

 tried with A. ; with B. it produced a deep blue colour, and with 

 C. the same colour, but of a lighter shade. 



I may here remark, that when the dark green precipitates 

 produced by hydrosulphate of ammonia from the solutions 

 of Davidsonite, and of alumina and oxide of iron, were ex- 

 posed to the air for about 12 hours, they were both con- 

 verted into a brownish white gelatinous substance. 



The remaining solution of Davidsonite, and an equal quan- 

 tity of the alumina and iron, were then respectively treated 

 with excess of potash, which in both cases redissolved the 

 precipitate at first produced, except a small portion of a 

 reddish brown gelatinous substance, which when dissolved in 

 hydrochloric acid, and tested with ferrocyanate of potash, 

 and tincture of galls, in each instance afforded abundant in- 

 dication of oxide of iron. 



The alkaline solutions having been respectively neutralized 

 and the precipitates redissolved in hydrochloric acid, were 

 boiled down in flasks to about 1| fluid ounce; and both of these 

 solutions afforded, with the tests already noticed, precipitates 

 precisely similar to those they gave previously to the addition 

 of the caustic potash, with the exceptions of ferrocyanate of 

 potash and tincture of galls, neither of which produced the 

 slightest discoloration; the colour also of the precipitates pro- 

 duced by hydrosulphate of ammonia was an extremely light 

 shade of green, very different from that produced before the 

 addition of potash*. 



From these experiments it would appear, that the sub- 

 stance combined with silica in Davidsonite, and alumina 

 mixed with a minute quantity of oxide of iron, are identical, 



• The solution of potash employed became tinted on the addition of 

 hydrosulphuric acid. 



