What is a Litmus Test?

A litmus test initially meant a simple technique to identify whether something to be acidic or basic. It climate morphed into an expression meaning a test that offers a basic yes or no answer. It transforms out the a genuine litmus check isn’t constantly so “black and also white”.

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Litmus Paper-Red or Blue?

When we think the litmus paper, the colour red and blue concerned mind. It transforms out there is likewise a gray area, or purple, to be more accurate. The shade of litmus is only solid red below pH 4.5 and solid blue over pH 8.3. Indigenous pH 4.5 come pH 8.3 the shade goes through shades that purple as you deserve to see in the top strip in the photo below.


The picture shows a strip whereby one finish was dipped in acid pH pH8.3. The lighter purple in the center is neutral pH 7. The bottom strip’s main section has actually no litmus in that all. (Image source: Wikipedia)

You deserve to test this for yourself further with few of the liquids in the graph below. Girlfriend will see that litmus paper can only give a critical yes or no for acid/base for few of them.


pH the Things about the House

You can show the nature of a litmus test utilizing the liquids listed below. You will watch for yourself that litmus record test have the right to only check the most acidic or basic ones yet not the persons closer to neutral pH 7


Litmus document Tests

Drop lemon juice top top red litmus paper, nothing happens. Autumn milk that magnesia top top blue litmus paper, again, naught happens. Switch the shade of the papers, repeat, and also observe the change.

An interesting feature of litmus is that the color readjust is reversible. Fall lemon juice ~ above the milk of magnesia spot and also milk that magnesia top top the lemon juice spot and see what happens.

Try this with different liquids. What happens if you make a spot v a weak basic & climate drop a strong acid top top it. Or, a strong base & then a weak acid? There are all sorts of possibilities.

If you have actually an imaginative streak, you have the right to evoke her inner Jackson Pollock and also create weird and wonderful patterns prefer those listed below on the 8×10″ (200x250mm) sheets that litmus paper.


2 huge sheets that litmus, 1 red & 1 blue room compared. The one top top the appropriate is red litmus sprayed through an alkaline solution. The one on the left is red litmus sprayed v acid.

Litmus test Chemistry

So why walk litmus behave this way? It’s since of 7-hydroxyphenoxazone. As soon as exposed to acids below pH 4.5, the molecule looks like the photo below and this offers litmus paper its red color. Together the pH the the test systems moves in the direction of alkaline, one of the hydrogen atom (white hemispheres) starts to break off (disassociate). In the photo below, it is the hydrogen at the bottom left.

As the pH viewpoints neutrality (pH 7) an ext and an ext of the indicator molecules shed this hydrogen atom. In ~ pH7, half the litmus molecules will certainly still have actually this hydrogen in place and also the other fifty percent won’t. This mixture to produce shades of purple in the mid-range. As soon as the equipment goes to alkaline pH 8.3 or higher, all the hydrogen will have disassociated and also the litmus indicator is currently blue.


Video: utilizing Litmus paper for basic Identification of acids & Bases

Litmus file vs pH Strips

Since litmus file gives indeterminate results roughly neutral pH 7 one needs to consider alternate tests in this range. A pH meter is one option but this is reasonably expensive and also not recommended for science fair or homeschooling use.

pH check strips use various chemical indicators. Some have actually just one indicator that reacts in a narrow range such as pH 3-6. Other test strips usage several indicators which deserve to work v a wider range the pH levels. Friend can also choose between strictly basic pH 7-14 strips or acid pH 0-7 strips. Or, use ones the cover a really wide selection of mountain & basic such together the pH 1 to 14, or simply the ones on either next of neutral prefer the pH 4.5-10 check strips.


Try these combination packs the pH & litmus check strips. We have put with each other 3 various bundles that include a vial every of 100 blue and 100 red litmus papers and also some various pH strips.

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pH/Litmus Choices

You have the right to do exciting experiments v these litmus document and pH strip mix packs; view the list in the 3rd of pH/litmus paper.