Macherey-Nagel qualitative indicator paper for whether a sample is acid, in 3 presentations covering different measuring ranges.
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A qualitative indicator paper that shows whether a sample is acid, by turning from blue to red. It gives a yes or a no, not a value.
Litmus does not measure pH; it answers one question — acid or not — and answers it unambiguously. That is often the whole question: has the acid rinse reached this point, is this drum what the label says, did the neutralisation work.
A qualitative paper does one thing and does it without ambiguity. There is no scale to interpolate and no lighting to argue about: the colour changes or it does not.
That makes it the right tool when the decision is binary — proceed or do not — and the wrong tool when anyone needs to know how far past the threshold the sample is. For a value, use an indicator paper with a scale or a meter.
Blue paper detects acids; a sample that leaves it blue may be neutral or alkaline, and red paper is needed to tell those apart.
Supplied in 3 presentations covering different measuring ranges. The range is chosen by model: 5.0.