CHAPTER XXIII. 



ACIDS. 



66. SULPHURIC ACID. 



i. Action of heat on green vitriol. Fit a hard glass test-tube with a 

 long right-angled delivery tube. Half fill the test-tube with powdered 

 green vitriol. Fix in a horizontal position in a 

 clamp attached to a retort stand. Let the end 

 of the delivery tube lead into a test-tube. 



Gentle heating. Heat very gently till no 

 further change is observed. It will be found 

 that the green vitriol turns a dirty white colour, 

 and that a clear liquid collects in the receiving 

 test-tube. Remove and identify the liquid. 



Strong heating. Put a second test-tube under 

 the delivery tube and continue heating at as 

 high a temperature as possible. It is noticed 

 that white fumes with a choking odour are 

 given off, and that they condense to an oily- 

 looking liquid in the receiving tube. Examine 

 the solid remaining in the tube. Is it soluble 

 in water ? 



Sulphuric acid. When green vitriol is 

 heated it is found that at first a colourless 

 liquid is obtained in the receiving vessel, 

 and if a sufficient quantity of this liquid is 

 collected it is found to have the same boiling 

 point and the same density as water, and to 

 have all the other properties of water, which it is. On strongly heating, 

 fumes are given off which have a very sharp odour and condense to 

 form an oily liquid, which on account of its appearance and origin used 

 to be known as " oil of vitriol." It is better known as? sulphuric acid. 

 The acid of commerce is not prepared in this way, as it would be too 

 expensive. It is got from sulphur dioxide. Very large quantities of 

 sulphuric acid are used in manufacturing processes. The chief use 

 of sulphuric acid in Ireland i?? for the manufacture of artificial fertilizers. 



142 



FIG. 97a. Heating green 

 vitriol. 



