ph?

[djLeviatan]

i was just curious about what makes testers, eg. Marquis, react: is it the pH of the substance?
Just fooling around with my basic chemistry book found that this test, Universal Tester i think, has the same color ranges that Marquis and reacts upon subtances pH, this means: "Universal"=Marquis?
please...someone?

 

[easy e]

pH measuring paper is not the same as marquis.
without getting too technical, it works as follows:
the sulphuric acid both acts as a oxidant and a dehydrant and it forms colored p-quinoidal products when condensating with formaldehyde.
the exact route is not known but this should more or less cover it.
reactions may be influenced by the presence, or absence of a free para place on the ring.

 

[djLeviatan]

thank you very much