[1] Instructions are given for testing a single substrate. However, you should test multiple substrates simultaneously, but no more than you and your partner can comfortably handle and monitor. Do not start a test unless you are sure you can give the test mixture immediate and adequate attention. BACK TO PROCEDURE

[2] If a precipitate results from a substitution reaction, the amount should increase with time. The appearance of a trace of precipitate that does not increase with time, or after heating, is a suspect result. BACK TO PROCEDURE

[3] Be sure to record all observations that will help you detect reactivity patterns. The time for initial precipitate formation may not be enough. For example, suppose you conduct two tests. The first solution becomes cloudy immediately and becomes more cloudy so that bits of precipitate eventually settle to the bottom of the tube after 5 minutes, while the second solution forms a precipitate immediately that settles in a layer in the bottom of tube in less than 30 seconds. While the time for initial formation of precipitate (0 seconds) is identical in both tests, the second test clearly involves a faster reaction (faster buildup of precipitate) and should be described as such. BACK TO PROCEDURE