372 



Common Science 





FIG. 187. Making the test. 



run all through it. Then while it is still melted, shake the 

 bead out of the loop on to a clean plate. If it is dark colored 

 and cloudy, try again, getting a still smaller grain of the 

 chemical. You should get a bead that is transparent, but 

 clearly colored, like an emerald, topaz, or sapphire. 



Repeat with each of the six chemicals, so that you have a 

 set of six different-colored beads. 



This is a regular chemical test for certain elements 

 when they are combined with oxygen. The cobalt 

 will always change the borax bead to the blue you got ; 

 the chromium will make the bead emerald green or, in 

 certain kinds of flame, ruby red ; etc. If you wanted to 

 know whether or not certain substances contained co- 

 balt combined with oxygen, you could really find out by 

 taking a grain on a borax bead and seeing if it turned 

 blue. 



