18 



SCIENTIFIC AMUSEMENTS. 



(3) potassium iodide ; (4) caustic soda (sodium hydroxide) ; (5) 

 sulphuretted hydrogen (hydrogen sulphide) ; (6) sodium phosphate. 

 Now add a few drops of solution of silver nitrate to each. A 



Fig. 12. Clamp. 



precipitate will be formed in each glass by double decomposition, 

 the colour being different in each case. In the first glass a white 

 precipitate will be formed, sodium chloride and silver nitrate pro- 

 ducing sodium nitrate which remains dissolved, and silver chloride 

 which precipitates. In the second glass a dark red 

 precipitate of silver chromate will be formed together 

 with potassium nitrate in solution. In the third glass 

 pale yelloiv silver iodide is precipitated, whilst potas- 

 sium nitrate is again formed in solution. In the 

 fifth glass black silver sulphide is precipitated and 

 hydrogen nitrate (nitric acid) produced in solution. 

 In the fourth glass brown silver hydroxide is precipi- 

 tated, and in the sixth yellow silver phosphate, sodium 

 nitrate in solution being also formed in each case. 



Expt. 13. To produce a Gas Smelling like Rotten 

 Eggs by Double Decomposition. Put into a test- 

 tube a few grains of powdered iron sulphide and pour 

 over them a little diluted hydrochloric acid (solution of hydrogen 

 chloride). Double decomposition will take place, resulting in the 

 evolution of the gas hydrogen sulphide (the solution of which 



such as "iodide of potassium " and "potassium iodide," and so on. Of the 

 two forms of expression, perhaps the latter is the preferable one. 



Fig.13. 

 Test Glass. 



