The purpose of litmus paper in any solution is to determine the pH value, it is that is why called as the pH indicator. In the gravimetric method, litmus paper serves the same purpose and helps the observers detect the exact pH value. In case the paper turn red, the conditions are acidic, however it remains blue under alkaline or basic reactions. In case of neutral the litmus paper remains purple.
The reaction solution is tested with litmus paper in gravimetric method to determine pH value of the solution.
Explanation
Gravimetric method is quantitative method used to determine the weight of substance dissolved in a solvent chemically.
The substance is reacted chemically with the solvent and then the resultant substance is filtered to get the component followed by the measure of the weight of the desired substance.
The litmus paper is used to check the pH value of reaction solution.
The color change in the litmus paper decides the nature of the reaction solution.
The reaction solution is acid in nature, if the litmus paper turn in red color and the solution is base in nature if the litmus paper converts into blue color.
