ACIDS 143 



67. PROPERTIES OF SULPHURIC ACID. 



i. Density. Take a test-tube about one-third full of distilled water, and 

 carefully trickle about 1 c.c. of strong sulphuric acid down the side. Note 

 the effect. Does the acid sink ? 



ii. Solubility. Shake up the liquid in the last test. Does the acid dis- 

 solve in water ? Feel the outside of the test-tube. Is there any change 

 in temperature ? 



iii Taste. Take about half a cubic centimetre of the dilute solution 

 prepared in the last experiment and further dilute it. Observe the taste. 



iv. Action of dilute sulphuric acid on substances. Try the effect of 

 the dilute acid on the following substances and record your observations : 

 (a) litmus, (b) chaljc, (c) lime, (d) washing soda, (e) and the metals zinc, 

 iron, copper, magnesium. If a gas is given off, test the gas with moist 

 litmus and apply a flame to it. 



v. Action of strong sulphuric acid on substances. Try the effect of strong 

 sulphuric acid on each of the following : (a) wood, (6) salt, (c) nitre, (d) sal 

 ammoniac, (e) copper. If no action is observed, heat gently and carefully. 



Properties of sulphuric acid. Familiarly known as oil of vitriol, 

 sulphuric acid is one of the most important and useful of chemical 

 compounds. It is a heavy, oily liquid, which, when strongly heated, 

 boils at 335 C., and gives off a quantity of choking, pungent white 

 fumes. It mixes with water in all proportions, and produces during 

 the solution so much heat that the temperature may rise above 100 C. 

 the boiling point of pure water so that care has to be taken when 

 sulphuric acid and water are mixed. Sulphuric acid absorbs moisture 

 very readily, and, owing to this affinity for water, it chars organic- 

 matter, such as sugar and wood. When the strong acid is brought 

 into contact with sugar it abstracts water from the sugar, and a black 

 mass of carbon remains. Like most other strong acids, it burns the 

 skin and destroys cloth, so that care must be always taken in using it. 



This property of taking up water so greedily makes sulphuric acid a 

 valuable agent for drying gases. The dilute acid has a sour taste 

 and when added to washing soda effervescence takes place and a gas 

 is given off. The dilute acid dissolves the metals zinc, iron and mag- 

 nesium, and at the same time an inflammable gas is given off. No 

 action is observed with copper. The strong acid acts on salt and 

 on sal ammoniac. In each case clouds of fumes are given off which 

 immediately turn litmus paper pink. Copper dissolves in boiling 

 sulphuric acid, giving off a gas with an odour of burning sulphur. 



