NITRIC ACID AND NITROGEN COMPOUNDS 



be used for this experiment. If necessary, a brick or block may 

 be placed under the cylinder. The delivery tube should pass into 

 and nearly to the bottom of a test-tube which is immersed in cold 

 water in the cylinder. Put 15 cc. concen- 

 trated sulfuric acid (H 2 SO 4 ) and 10 

 grams of either sodium nitrate (NaNO 3 ) 

 or potassium nitrate (KNO 3 ) into the 

 flask and apply heat until about 4 or 5 cc. 

 of HNO 3 is distilled and collected in the 

 test-tube. Do not remove the flame un- 

 less the end of the delivery tube is above 

 the liquid in the test-tube, otherwise the 

 liquid will be drawn back into the flask. 



Make the following tests with HNO 3 . 

 ( i ) Remove a drop of the acid by means 

 of a glass tube, and apply it to either a 

 piece of woolen cloth or silk. Observe 

 the result. (2) Place a few drops of indigo 

 solution in a test-tube containing 5 cc. of 

 water, then add about 2 cc. of HNO 3 . Ob- 

 serve the result. (3) Place a small piece 

 of copper in the test-tube containing the 

 remainder of the acid. Observe the result. 

 If no reaction takes place, add a little 

 water. Do not pour the contents of the 

 flask into the sink or waste jars until 

 cool, otherwise the hot acid coming in contact with cold water 

 may cause spattering of the acid. 



Questions. ( i ) Why was H 2 SO 4 used in the preparation of this 

 compound? (2) What material supplied the NO 3 radical? (3) 

 Write the reaction which took place in the flask after heat was ap- 

 plied. (4) Is HNO 3 a solid, liquid, or gas? Why? (5) What caused 

 the red fumes to be given off when the copper was added to the 

 test-tube ? (6) Does HNO 3 give off H when a metal is added to it ? 

 Why? (7) Why did the HNO 3 bleach the indigo solution? (8) 

 Why is ordinary HNO 3 colored yellow? (9) Is HNO 3 an active or 

 inert chemical ? ( 10) What is a nitrate? 



Fig. 42. Preparation of 

 nitric acid. 



