I'll have a stab at this, please correct me if I'm wrong!.
1. potassium nitrate , 3 oxygen atoms decomposes at 400 oc
2 potassium chlorate ,3 oxygen atoms again decomps at 400 oc, but contains chlorine.
3 potassium perchlorate, 4 oxygen atoms , decomps 600 oc, again contains chlorine
my understanding is whilst the perc as more oxygen, the oxygen from the chlorate is more readily available at a lower temp , giving a cooler flame ideal for blues
4. potassium chlorate, while one oxygen atom less than potassium perchlorate, has a higher percentage of chlorine
5. potassium chlorate, aside decomposing at a lower temperature, also is more chemically instable overall, which makes it more willingly to react with other chemicals.
The dangerous and infamous potassium chlorate+sulfur gives the utmost colour depth together with barium nitrate, for instance. Only barium chlorate beats it.
Edited by Pyroswede, 27 September 2010 - 09:45 PM.