Memoir upon Ultra-marine. 36i 



3th, Exposed to the action of the electrical pile, the oxy- 

 genating side discolours it completely ; the hydrogenating 

 side occasions no change. 



6th, Oxygen gas alters the colour of ultra-marine exposed 

 to a red heat, it makes it turn to a dirty green ; there is an 

 augmentation in weight of one per cent., probably owing 

 to sulphuric acid which is formed and fixed. 



7th, Hydrogen gas, in the same circumstances as oxygen, 

 changes completely the colour of ultra-marine ; it gives it a 

 reddish colour, and takes off Us sulphur ; no water seems to 

 be formed, although there is a loss of weight exceeding a 

 little that of the sulphur. 



8th, Sulphur in fusion does not discolour it, and after 

 volatilization the ultra-marine is as beautiful as ever. 



9th, Liquid sulphurated hydrogen has no action upon it 

 at all. 



10th, Neither has lime water. 



11th, Barytes water discolours it when heated, and is 

 afterwards found to contain silex and alumine. 



12th, The sulphuric, nitric, muriatic, and oxymuriatic acids 

 suddenly discolour ultra-marine: the three former, when 

 concentrated, form with it a very thick jelly; the latter 

 acid dissolves it almost entirely. 



If the sulphuric and muriatic acids are diluted in water, 

 there is a liberation of sulphurated hydrogen ; the action of 

 the nitric acid produces nitrous gas and sulphuric acid. 



13th, The acetous acid acts like the above acids, but much 

 more feebly. 



14th, Potash and soda in solution, heated with ultra-ma- 

 rine, diminish its weight ; they then contain alumine. The 

 colour is not altered. 



If pure potash is heated strongly with ultra-marine, its 

 colour is destroyed ; the result of the fusion is reddish, and 

 acts almost as if the ultra-marine was argil, or a stone com- 

 posed of silex and alumine. 



15th, Ammonia has no action at all upon this substance. 

 1 6th, Upon heating oil with ultra-marine, the weight of 

 the latter is found to be diminished after washing it m an 



alkaline solution. 



17th, The 



