154 An Account of a Metear. 



tifige of green, a circumstance which v/as, doubtIcssi» 

 connected with the dark appearance of the magnesia, 

 when first heated. It shall be resumed presently. — It 

 should be observed, that in some of the experiments 

 with sulphuric acid on this supposed magnesia, a white 

 matter, in small quantity, remained undissolved at the 

 bottom of the vessel. — it could hardly be siiex, and pre- 

 liminary experiments led me to conclude that no lime 

 was present.— Was it accidental, or, was there a small 

 portion of akimine ? This white matter, when heated 

 with sulphuric acid and sulphat of potash, did not aiford 

 crystals of alum, on evaporation. I have not yet had 

 leisure fully to decide this point, but intend to resume 

 it. The stone has a very slight argillaceous smell, when 

 breathed upon. 



8. — The remaining solution still retained its greenish 

 colour. Previous trials had decided, that neither copper 

 nor iron was present in the solution. Nickel was there- 

 fore sought for, and the observations of Howard and 

 Vauquelin, in their analyses of the stone of Benares, led 

 me to expect it in triple combination with the ammoni- 

 acal nitrat and muriat, which had been formed in the 

 liquor by a previous step of the process.- According to 

 the experience of Howard, I found the hidro sulphuret, 

 and the prussiat of ammonia, the only agents among 

 those which I tried, that would precipitate the nickel. 

 The prussiat of ammonia gave a white precipitate, in- 

 clining to purple ; the hidro sulphuret of ammonia, a 

 voluminous black precipitate. The hidro sulphuret was 

 used, and the precipitate was separated by the filter ; the 

 filter was dried, and it was with great difficulty that about 

 three fourths of a grain were collected ; the portion ad- 

 hering to the filter was estimated at a grain \. that which 

 had been collected was ignited in a platinum crucible, 

 and became green ; it was, without doubt, the oxid of 

 nickel, and with every allowance for loss and other cir- 

 cumstances, the whole cannot be estimated at more than 

 1,5 grain. In this estimate is included a portion of nickel 

 which adhered to the magnesia, vv'hen it was precipitat- 

 ed; which caused it to turn black, when first heated — 

 which gave the sulphat of magnesia formed from it a 



