532 M. E. Bieuuliu on the Constitution of 



quantity, has an injurious action on the colour. It was long 

 known that silica, soda, and alumina gave, under no circum- 

 stances, a blue colour ; but from the investigations of the che- 

 mists above mentioned, as well as from the fact that ultramarine 

 treated with strong acids lost its colour luidcr evolution of sul- 

 phuretted hydrogen, it was evident that sulphur was the most 

 essential constituent. 



This has long been partially recognized, and it was assumed 

 that the sulphur was in combination with iron. 



Briinner considers that the sulphur is united with the soda, 

 partly as monosulphide of sodium, and partly as sulphate of 

 soda. His view is grounded on this experiment. 



He took an ultramarine basis, which was of a greenish-blue 

 colour, and ignited it several times with carbonate of soda and 

 sulphur, by which the mass became darker ; he then mixed it 

 with finely divided sulphur, and heated it in the air. The mass 

 increased in weight. The uuburnt mass contained 5'198 per 

 cent, sulphur. By burning, it increased in weight 10"16 per 

 cent., and contained after the burning 12'81 per cent, sulphur. 

 The increase of weight consisted of 7"618 per cent, sulphur 

 + 2'542 per cent, oxygen = 10' IG per cent. 



The analysis of the unburned ultramarine gave — 



100-000 

 But since 100 parts in burning became 110*16, in which 12*81 

 sulphur are contained, the rest of the constituents remaining the 

 same, the ultramarine after burning must consist of — 



100-000 



Briimrer calculated and found that 20*157 parts of sulphate of 

 soda corresponded to 9*039 per cent, oxygen : he subtracted the 

 quantities of sodium and sulphur contained therein from 11*639 



