Memoir upon Ulira-mar'me. 363 



AH these crystals, and the liquor remaining, yielded, by 

 means of ammonia, 6-85 of dry alumine, and melted in the 

 fire 9*60 of sulphate of soda. 



We have seen, by other experiments, that the alumine and 

 soda were generally in greater quantity than that indicated 

 by the action of the sulphuric acid. 



On passing muriatic acid gas through water in which 20 

 grammes of ultra-marine was incessantly agitated for some 

 time, we dissolved 18-48. The remainder, being 1*52, had 

 all the characters of silex. We obtained from the solution 4'6 

 of dry alumine; muriate of soda, containing about four 

 grammes of alkali ; and lastly, sulphate of barytes, contain- 

 ing six decigrammes of sulphur, supposing it composed of 

 J %dths of sulphuric acid, and the latter of -j^dths of sul- 

 phur. 



If with alcohol we treat the result of the fusion of twenty 

 grammes of potash with five grammes of ultra-marine, the 

 weight of the latter is diminished one gramme, and the al- 

 cohol contains but very little silex and alumine; this loss is 

 evidently owing to the soda of the ultra-marine, which aban- 

 dons the other principles, because their combination was 

 broken by the potash in the fire. 



Upon treating of ultra-marine by carbonated soda, we 

 got from 10 grammes 3*3 of silex, which had all its proper 

 qualities in a less equivocal degree than it had formerly pre- 

 sented, when arising from ultra-marine treated by the acids 

 or caustic alkalis. We thought at first that it contained 

 some foreign substance, but we could not discover any. 

 In order to characterize this silex properly we employed the 

 usual methods ; among others, volatilization by the fluoric 

 acid, which left it deposited like a jelly in the water which 

 it had passed through. 



Thus ultra-marine yields on being decomposed, silex, 

 alumine, soda, and sulphur. 



Let it be recollected that this precious substance, such as 

 the present process of extracting it affords, contains oily 

 particles ; that soda is one of its elements ; and it may be 

 added, that the water, which was .-nade use of to separate the 

 ultra-marine from the mastic with which it was incorporated 



in 



