Why is it good to use blue and red litmus for the same solution?

Under acidic conditions, the solution is red, and under alkaline conditions, the solution is blue. Chemical reactions other than acid-base can also cause a color change to litmus paper. For instance, chlorine gas turns blue litmus paper white – the litmus dye is bleached, because of presence of hypochlorite ions.

metric time was an attempt to create a standard unit of time based off of 10, but it never took off an is not included in the metric system (si)