536 



M. E. Breunlin on the Constitution of 



Nos. III. and IV. are kinds of a clear pale blue; the others, I., 

 II. and v., are of the finest sorts ; it may hence be assumed, 

 that, in chemically pure blue, 1 equivalent of pentasulphidc of 

 sodium corresponds to 4 equivalents of soda in the silicate ; 

 and in the purest green, 1 equivalent of bisulphide of sodium 

 corresponds to 2 equivalents of soda in the silicate, or in other 

 words, — 



In blue, 2 equivs. nepheline with 1 Na S^ 

 In green, 1 equiv. nepheline with 1 Na S^. 



The formuliE for the pure compounds are accordingly, — 



Blue2((2NaO)Si03 + 2(AP03Si03)) + lNaS'* 



1 ((2NaO)Si03 + 2(AP 03 Si03)) + INa S^. 



In order to compare the values of the constituents of the pure 

 compound as found by analysis, with the per-ccntages as calcu- 

 lated from the formula, the impurities, oxide of iron, clay, and 

 gypsum, were rejected, and the weights of the bodies constituting 

 the pure compound calculated for 100. For the blue ultramarine 

 the foUowin"; constitution is obtained : — 



