Litmus paper is a type of material that helps people who work with machines. The litmus paper tells them if its acid or neutral. You would get the litmus paper and would dip it in the liquid and it will tell you if it's acid or neutral. How? The paper changes colour then you match the colour to the number .The numbers are from 1 to 14.
What the numbers mean:
0 to 2 =strongly acid HAZARD
3 to 5= Moderately MILD HAZARD
6= Mildly acid No real danger
7.0=Neutral .Non hazard
8 to 9 =Mildly Alkaline . No real danger.
10-12 Strongly alkaline with a mild hazard.
12-14 Caustic and strongly alkaline.