1823.] the same Crystalline Form as Pyroxene. 229 



Silica 63*21 containing oxygen 31*79 



Lime 5*18 1*45 



Magnesia 26*26 10*16 



Protoxide of iron 4*36 0*99 



Oxide of manganese . . 0*82 



99*83 



It is clear that a great surplus of silica exists in this mineral, 

 and that it is not a bisilicate. This exception to the common 

 rule which existed in every other analysis was unexpected. 

 M. Rose repeated the analysis twice, but always obtained the 

 same result. Fragments of it, when distilled in a small appara, 

 tus, gave out water, which did not change any of the test papers. 

 M. Rose endeavoured to find fluoric acid in this sahlite by melting 

 it with carbonate of soda, dissolving the mass in water, evaporating 

 the liquid to a small bulk, separating it from the silica, supersatu- 

 rating it with muriatic acid, mixing it with excess of ammonia, 

 and adding muriate of lime, after which the vessel was carefully 

 closed. No precipitate of filiate of lime appeared, not even after 

 several days ; and only a trace of silica was deposited.* 



A considerable quantity of another sahlite was distilled in a 

 porcelain retort; the loss amounted to 3*17 per cent. Water 

 was distilled, and at last fumes passed through the aperture 

 of the receiver, which smelt like a mixture of sulphurous 

 and sulphuretted hydrogen. The water in the receiver was 

 slightly sour ; when saturated with ammonia, and slowly eva- 

 porated in a stove, it left only a small trace of salt of ammonia, 

 which, when heated, evaporated like muriate of ammonia, and 

 before the blowpipe with silica and soda, gave a brown button. 

 By another distillation, when the receiver was kept very cold, 

 a fluid was obtained, which, in the beginning, was turbid, smelt 

 of sulphur, and on being saturated with ammonia, visible traces of 

 sulphur were thrown down. When the sulphur had been sepa- 

 rated, this solution was evaporated ; the same salt remained as 

 before, the brown colour which it communicated before the 

 blowpipe to the glass of silica and soda, proved to be sul- 

 phate of ammonia. This sulphurous acid evidently derives 

 its origin from the sulphuret of lead which occurs dissemi- 

 nated in the sahlite. The very insignificant quantity shows that 

 it cannot be the produce of one of the constituent parts of the 

 sahlite (the water of a perfectly pure sahlite, of which the analysis 

 lnis been communicated above, did not contain any trace of 

 it). Besides the sulphurous smell, an empyreumatic one 

 was observed in the water, which is peculiar to the water 



When the liquid which had been separated from the silica was evaporated to a 

 small hulk, and a mixture of sulphuric acid and alcohol poured on it, it burned with a 

 green flame, which, however, depended upon the muriatic ether, and not on boracic 

 acid. 



