The litmus test is a chemically treated litmus infusion
paper. It is used to determine the degree of acidity or alkalinity of the medium. Before the paper was impregnated with litmus, it was used separately as an indicator and a chemical reagent. The Spanish alchemist Arnaldu de Vilanova first used litmus as an indicator in about 1300. This substance is of natural origin, it is obtained from lichens.
The litmus test is an acid-base indicator, which turns red in an acidic environment and blue in an alkaline environment . Depending on the color intensity, using a special scale, determine the pH of the medium. A hydrogen index or pH is a quantitative measure of the ratio of H + and OH- ions in water, which were formed during the dissociation of water. At room temperature in a neutral solution, pH = 7, in acidic pH <7, alkaline pH> 7.
Litmus paper in practice is used in a rather easy way: you need to take it in one
end and lower the other into the liquid medium. No need to dip paper deep into the liquid. The result appears immediately: the edge lowered into the medium either changes its color or not. Then this paper is compared with the standard values, which are printed in the form of a scale on the tube or package in which the indicator was located. The litmus test is considered a universal indicator, as using it, you can determine the degree of both acidity and alkalinity of the medium.
This indicator can be made at home, while spending a minimum of money and time. To do this, you need red, blue or purple cabbage, filter or plain white paper. Grate the cabbage on a fine grater, boil for 30-35 minutes, and then gently strain and squeeze. Cabbage itself will not be needed in the future, and in the resulting broth you need to put strips cut out of paper. After the paper has been soaked, remove and dry it. You need to store such paper in a dry container, away from sunlight. When using such a home-made indicator, it must be taken into account that it gives a slightly larger measurement error than the factory one.
Litmus test due to ease of use and versatility in
With regard to determining pH, it was widely used not only during chemical experiments in educational institutions and clinical laboratories, but also in everyday life. So, anyone with ease using a litmus paper can determine the hydrogen index of any biological fluid, solutions, mixtures - saliva, urine, breast milk, water, soap, etc. The parameters of pH-biological fluids must be independently controlled for certain diseases. Also, litmus paper is actively used by flower growers at home to determine the degree of acidity and alkalinity of the soil. You can use it to determine the pH of cosmetics, in particular those that are used for skin care, because ideally, they should be neutral.