TLTUAMARINE. l3Q 



(ItfTieuU than that of astone of an analogous composition 

 Mould be, though it is very readily attacked both by acids 

 and alkalis. The disunion of its principles is not com- 

 plete till after the most decided action of ejich of the 

 reagents employed. 



The quality of the ultramarine we nsed, which we Component 

 cannot consider as perfectly pure, and the variation that P^^^*' 

 must occur in the proportions of its constituent principles, 

 induced us to study their nature rather than their quan- 

 tities. To the knowledge of each of these principles we 

 devoted a separate portion of ultramarine; and it is from 

 these results united, that we conclude a hundred parts of 

 ultramarine to be composed nearly of 



Silex 35 8 



Alumine ......34 .8 



Soda ...:...:. 23 2 



Sulphur 3 1 



Carbonated lime ..... 3 1 



100 



We always experienced a loss of about five per cent,; Loss. 

 sometimes more. 



The carbonated lime we discovered is not essential to Carbonate of 

 the composition of ultramarine, any more than the irori, ^^"^^■ 

 which we did not meet with in ultramarine of the first 

 quality procured from a lazulite little charged w ith sul- 

 phurated iron. It is not the same with sulphur, whicli Sulphur, 

 alwajs occurs. 



The following is the mode in which we ascertained the Processes of 

 nature of the four substances, that appear to us essential analyzadon. 

 to ultramarine. 



Thirty granjmes [an ounce] of fine ultramine, heated 

 with sulphuric acid, left ^ residuum weighing 14 grammes. 

 The liquor on evaporation exhibited a few crystals of 

 alum*, and a great deal of sulphate of soda in long Alumine an4 

 jieedles. «o^^- 



* It Is probable that the alcaU, which occasioned the crystalliz- 

 ation of this sulphate of alumine, was potash proceeding from the 

 ultramarine: we do not affirm this, however, 4>ecause we had n«t 

 secured the salt from the anjmoniacal vapours, that might havp 

 existed in the laboratory. 



T 2 AU 



