Hi Ian,
I think the burn test part of your question has been answered far better than i could advise you, so ill move right on to pH.
pH speaking scientifically is a measure of the concentration of protons (H+) in an aqueous medium. "the logarithm of the reciprocal of hydrogen-ion concentration in gram atoms per litre" [1] which in ley-mans terms is a measure of how acidic/alkali any given water based solution is.
So what use is it? Well anything that is dissovled in water has the potential to affect the pH of water. Indeed, pure distilled and degassed water has a pH of 7, but as soon as you introduce a soluble liquid/solid to the water this may change. [2]
The pH scale runs from 0-7-14.
0-6.9 = Acidic. Whereby the closer you get to zero the more acidic the solution is. e.g pH 2 = more acidic than pH 6.
7.1-14 = Alkaline or Basic. Again the further you get from 7 the more alkai the soultion is.
Its not a linear scale, its a logarithmic scale and this means: for example pH8 is 10 times less alkali than pH9. It increases in factors of ten, therefore pH10 is 100 times more alkali than pH8 etc etc. So pH14 is 10million times more alkai than pH8.
Who cares, im a carpet cleaner!: Well the implications of all of this is that fibres, in particular wool will degrade if you dont use the correct pH of solution to begin with. Basically, this means that if you dont selct the correct cleaning product (and therefore pH) you will be the proud owner of a new carpet. Moreover, you should never leave a carpet with a highly acidic or alkali residue on it no matter what its made of.
So pH is you friend. Not only will it guide you in what product to use in any given situation but also, It will tell you how well you have rinsed the carpet as you can check the pH of your rinse waste and see if its close to pH7(neutral). If not, you can add the approipriate acid/alkali and rerinse.
I hope this is of some help to you, but seriously if you dont understand the implications of both fibre identification and pH you should seek some training options. I think all of the major training programmes will cover them as they are the fundamentals of cleaning science.
Cheers
Graeme
ACS
[1] :
http://en.wikipedia.org/wiki/PH[2] :
http://www.miamisci.org/ph/ {play with the explore option}