In the qualitative identification of polymers, why should we do combustion test and dissolution test at the same time?

Practice has proved that most common polymers can be identified by comprehensive utilization of combustion test and dissolution test.

The test method is as follows: in the combustion test, a small amount of samples (about 65,438+000 mg) are put on a metal plate and burned with a small fire, and the combustion conditions of the samples are observed, including the difficulty of combustion, the shape change of the samples, the color of the flame and the situation after the samples leave the flame, and the smell of their decomposition products is also smelled. Another small sample (about 1 0 0 mg) was placed in a small test tube, and the bottom of the test tube was heated with a big fire. When the sample is decomposed by heat and gas is released, put a small piece of litmus test paper or pH test paper wetted with water at the mouth of the test tube to check the pH of the decomposed product. If parallel experiments are carried out with some known polymers, some polymers can be identified by referring to their common characteristics.