154 INTRODUCTION TO GENERAL SCIENCE 



Materials: Hydrochloric acid, 1-4; common salt, silver 

 nitrate solution, 5 per cent; sulphuric acid, 1-6; copper sul- 

 phate solution, 10 per cent; barium chloride solution, 5 per 

 cent; ammonium sulphide, 10 per cent; lead nitrate solution, 

 5 per cent. 



a. Dissolve some salt in a little water and taste it. Filter 

 and taste. Did the salt pass through the filter paper ? Put 

 the salt solution in the evaporating dish, on the asbestos mat, 

 and boil slowly to dryness. How does the amount of salt 

 compare with the original amount ? If sand and sugar became 

 mixed, how could you separate them? 



b. Take a teaspoonful of silver nitrate solution and filter 

 it. Does anything remain on the filter paper ? Now add 

 a few drops of hydrochloric acid, and filter. The acid has 

 changed the silver nitrate, which is soluble, into the insoluble 

 silver chloride. There is no more silver in the solution. 

 Repeat, using a solution of salt in the place of hydrochloric 

 acid. Silver nitrate, then, is a test for a chloride. 



c. Try the .effect of the solution of barium chloride upon 

 solutions of copper sulphate, and sulphuric acid. Note that 

 the addition of hydrochloric acid produces no effect. If barium 

 chloride produces a white precipitate in any liquid, in the 

 presence of hydrochloric acid, it indicates that there was a 

 sulphate present. 



d. Try the effect of ammonium sulphide upon a solution 

 of lead nitrate. Try the effect of lead nitrate upon a solution 

 of ammonium sulphide. Each is a test for the other. A 

 solution of lead nitrate is a test for the presence of any sul- 

 phide. . 



