ACIDS 



145 



(d) Firmly pressing the glass plate, invert a cylinder full of the gas and 

 place it upside down in a basin of water. Remove the plate when the mouth 

 of the jar is under water, and notice that water rushes up and completely 

 fills the jar. If the water does not completely fill the jar, it shows that the 

 air in the jar was not altogether displaced by the gas when you should have 

 filled it. 



(e) Place a piece of blue litmus paper in an empty gas jar, and tilt a jar 

 of the gas over it. Note the effect. 



iv. To make a solution of hydrochloric acid. Modify the apparatus in 

 Fig. 98 by removing the drying bottle, and attach the delivery tube direct 

 to the flask. To the end of the delivery 

 tube attach, by means of a short piece 

 of rubber tubing, a funnel. Place this 

 dipping into distilled water in a beaker, 

 as shown in Fig. 99. Care must be 

 taken that the funnel is so arranged 

 that, if the water is sucked back, it 

 will not be able to fill it. 



If there is still enough salt and sul- 

 phuric acid in the flask, again warm it 

 gently and allow the evolved gas to 

 bubble into the water. Notice that it 

 is completely dissolved. The solution 

 of hydrochloric acid gas formed in this 

 way is the " hydrochloric acid " of 

 commerce. 



Hydrochloric acid gas. When 

 common salt is heated with strong Fia 99 -~ Ma ^ffiri C S tion f hydr ' 

 sulphuric acid a gas is given off 



which forms steamy fumes in the air. The gas readily dissolves in 

 water, and the solution constitutes the hydrochloric acid of commerce. 

 The solution was, because of its preparation from salt, originally known 

 as " Spirits of Salt." Another common name given to it is "Muriatic 

 Acid." The "salt gas" itself is called hydrochloric acid gas. It is 

 colourless, will not allow things to burn in it, nor will it burn itself. 

 As i? seen by its action on blue litmus paper, it is strongly acid. It is 

 heavier than air, and can consequently be collected by downward 

 displacement. 



69. PROPERTIES OF HYDROCHLORIC ACID SOLUTION. 



i. Taste. Make a very dilute solution of hydrochloric acid and taste it. 



ii. Effect of heat on the solution. Take about one c.c. of concentrated 

 hydrochloric acid in a test-tube, and boil it. Try to expel the gas. Do you 

 succeed t Repeat, using a very dilute solution. 



iii. Action of the solution on substances. Try the action of the solu- 

 tion on each of the following : (a) litmus, (6) chalk, (c) lime, (d) wood, and 

 on the metals zinc, iron, copper and magnesium. 

 J.o.s. K 



