Chemistry

Hydrogenionic Product -pH (continued)


How to measure pH in practice?

The apparatus used to measure pH is the pH meter or parameter. They are devices that measure the electrical conductivity of the solution and have a scale already graduated in pH values.

Place the electrode into the desired pH solution and read the parameter.

Also used are several acid-base indicators (organic substances that change color in contact with acidic and basic substances), such as phenolphthalein, bromothymol blue and methyl orange.  

Here's the color that key indicators can get when they come in contact with an acid or base:

INDICATOR

ACID

BASE

NEUTRAL

Phenolphthalein

COLORLESS

ROSE

COLORLESS

LITMUS

ROSE

BLUE

-

Phenolphthalein in basic medium

Generally, the pH turning of these indicators occurs in different pH ranges.

It is also widely used the universal indicators, which are a mixture of various indicator substances. It is a scale with pH and color values. The color of these indicators varies gradually, showing the pH of the solution. It is widely used in chemical laboratories.

Another indicator widely used in laboratories is the litmus paper, which is a litmus impregnated filter paper. It is improper to indicate an exact pH value. Shows only if the solution is acidic or basic. If the paper turns red, the solution is acidic. If the paper turns blue, the solution is basic.