Potatoes, like the majority of vegetables, are a low-acid food with a pH value of 6.1.
Each brand of pH test strips may have slightly different color schemes.
Litmus paper comes in two colors. Red litmus paper turns blue when exposed to a base. Blue litmus paper turns red in the presence of an acid. Litmus paper is of limited use since it only tells you whether you are dealing with an acid or base and gives no indication about strength.
Universal indicator paper would show a very light yellow. Hydrion paper would show a 'dirty' yellow.
it turns acidic or very basic
Mauve on the pH paper Merck art. 9565.
When dipped in lemon juice, pH paper typically turns red or pink. This indicates that the lemon juice is acidic.
It would remain red, red litmus paper only reacts to blue in the presence of a base. Lemon juice is acidic and thus wouldn't turn the paper a color. If blue litmus paper was used in the lemon juice it would turn red. Consequently dipping blue litmus paper in a base won't change the color because it does not react with bases, only acids.
Blue litmus paper will likely remain blue when dipped in spinach as spinach is not acidic enough to cause a color change to red.
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blue
it turns acidic or very basic
Mauve on the pH paper Merck art. 9565.
Potato juice is typically neutral or slightly acidic, so if you test it with litmus paper, blue litmus paper will remain blue, and red litmus paper will remain red. This indicates that potato juice does not change the color of either type of litmus paper, reflecting its neutral pH.
Lemon juice contains citric acid so blue litmus paper dipped in lemon juice will turn red indicating that it is acidic.
When dipped in lemon juice, pH paper typically turns red or pink. This indicates that the lemon juice is acidic.
blue
Red
Lemon juice is an acid and blue litmus paper turns red when dipped in an acidic liquid.
It would remain red, red litmus paper only reacts to blue in the presence of a base. Lemon juice is acidic and thus wouldn't turn the paper a color. If blue litmus paper was used in the lemon juice it would turn red. Consequently dipping blue litmus paper in a base won't change the color because it does not react with bases, only acids.
It will become red !