Blue, Red, and Purple Litmus Paper Differences

There are three colors of the litmus test paper, which are red, blue, and purple. Litmus paper is a pH indicator made of filter paper soaked in litmus solution. Litmus is a mixture of dyes that changes color depending on the acid or base it is exposed to. They have different emphases on the detection direction when testing the sample solution. Litmus paper can only be blue, red, or purple.

Sometimes people refer to all pH paper as “litmus paper”. But this is not the correct statement. Many other indicators are used as dyes for pH paper, which produce other specific colors when in contact with the corresponding analyte. But what we mainly introduce today are the three litmus test papers mentioned above. Let’s check out:

What Are These Three Kinds of Litmus Test Paper?

Litmus liquid turns red in acidic solution, blue in alkaline solution, and does not change color in neutral solution. This chemical property allows red litmus paper to be used to test alkaline solutions. When the test paper is placed in the alkaline solution and taken out for inspection, an obvious color change will be observed: turning blue.

The blue litmus test paper will turn red when the reaction occurs, which is a signal strip used to detect the presence of acidic substances.

The dyes used in the blue and red litmus paper are included in the purple litmus paper, so they can detect both acidity and alkalinity. It will produce a color similar to that of the red and blue litmus test paper according to the acidity and alkalinity, that is, it turns red when encountering acid, and blue when encountering alkali. The stronger the acidity and alkalinity, the darker the color.

Blue, Red, and Purple Paper Differences

The difference in color is the most intuitive and obvious point. In addition to the obvious distinction of their own colors, they also behave differently after reacting with the detected objects.

It can also be said that they have different detection substances, and when the corresponding solutions are detected, the detection results presented are not the same. The red litmus strip turns blue when it detects an alkali, and the blue litmus strip turns red when it detects an acid. The purple litmus strip can detect both acid and alkali, and it can change to the corresponding color when it encounters the corresponding detected substance. And with pH=7 as the definition, the lower the value, the brighter the red, and the higher the pH, the darker the blue.

Here is a fun fact: the litmus strip that changes from red to blue after testing the solution can be used as blue litmus test paper. In turn, it can also be used as a blue test strip after the red turns blue. This method can be used when you are in a hurry, and it can also reduce some waste.
But it’s a contingency plan that shouldn’t be used excessively. Because some of the previous residues may interfere with the new test results. The new test paper is more accurate and reliable, it is a very cheap and environmentally friendly thing, and it is a little helper that can be used with peace of mind. If you need to buy Litmus Test Paper, you can see Hawach determination test strip. Universal pH strips and healthy pH strips are also full-prepared for you.