196 Chemistry. [Lecture 30. 



of charcoal in powder, it is converted into a sul- 

 phuret of barytes. The nature of this process 

 you will easily comprehend. The oxygen of the 

 sulphuric acid combines with the charcoal, and 

 goes off in carbonic acid gas, leaving the sulphur 

 behind with the baryta. The compound is dis- 

 solved in water, and nitric acid being poured 

 upon it, the sulphur is precipitated. The nitric 

 acid is afterwards driven off by heat, and oxide 

 of baryta remains. 



Baryta does not combine with oxygen, azote, 

 the alkalies, or metals ; but it unites and forms 

 compounds with sulphur, phosphorus, and the 

 mineral acids. It is used, though sparingly, in 

 medicine, and some of its compounds as tests in 

 chemistry. 



Baryta has been discovered by Davy to be 

 an oxide of a metal, of a dark grey colour, and 

 twice as heavy as water. This metal is named 

 Barium. 



VI. STRONTIAN is an earth, the oxide of stron- 

 tium, lately discovered, and takes its name from 

 the strontian lead-mine in Argyleshire, where it 

 was first found. It is always found combined 

 with the carbonic or sulphuric acid. It is of a 

 greyish-white colour ; its taste acrid and alkaline ; 

 it converts vegetable blues to green, and has the 

 singular property of tingeing flame of a beautiful 

 red, or rather purple colour. It has not as yet 

 been applied to any use in the arts. 



VII. YTTRIA is also an earth, lately discovered 



