On the Colouring-'Principh of Lapis Lazuli. 319 



treated in a crucible. A fulfure being formed, it was de- 

 compofed by the muriatic acid, which feized on the lini« 

 and the iron, while the filex remained mixed with the fuper- 

 abundant carbon. 



D. The liquors arifing from the three operations were 

 united, and then divided into two equal portions. From 

 the lirlt we feparated iron, which was found to weigh 1-05 

 grammes ; and I affurcd myfelf that it contained no other 

 earth but lime. We drew from the fecond 8 decagrammes 

 of lime. The whole liquor, therefore, contained, according 

 to the proportions determined by Klaproth, 



Oxydofiron - - 2-1 grammes. 

 Lime - - - 16 



Sulphuric acid - - T<^t 



Y.. It remained to examine the portion of earth left by the 

 acid, and which was found mixed with the fuperahundant 

 carbon. Here the operations began to prefent thofe unex- 

 peded phenomena, which, deviating from the ordinary 

 courfe, inform the attentive chemift that he is advancing 

 towards a difcovery. This refiduum was firft calcined ia aa 

 open veffel to confume the carbon, but the filex remaineJ 

 black: it weighed 1-65. It was treated with pot-afii in a 

 crucible of platina, and gave a fufed mafs of a fuperb blus 

 colour. Water poured over it aflumed the fame colour, 

 The nitric acid made it entirely dlfappear. The filex, fepa- 

 rated by evaporating to di^nefs, weighed no more than o-85 

 grammes. 



F. It now became of importance to know the effedl of 

 different re-agents on the nitric acid which had been poured 

 over the mafs fufed in the crucible, with a view to difcover 

 the fubftance that had given it thefe properties. The fol^ 

 lowing are the refults of thefe trials : 



I, With the prufllat of pot-a(h this liquor gave a precipi- 

 tate of a yellowifli-green colour, which the addition of 

 acids inftead of converting into blue, made immediately dif- 

 appear. 



a. With the gallic acid there was no precipitate. 



3. With fulphuratcd hydrogen there was no precipitate, 



a£ 



