Litmus is a dye of natural origin which is one of the most known acid-base indicators. Litmus everywhere is used – in medicine, the industry, chemical laboratories, in school experiments at chemistry lessons, even in advertizing you could see litmus.
Instruction
1. In practice several forms of litmus are used. It is water solution of substance, the strips of filter paper impregnated with litmus known as litmus paper, and litmus milk.
2. Originally litmus was prepared from an annual grassy plant of family the Spurge family hrozifor of a tinctorial, or litmus grass. Also for its production use some lichens. Vegetable raw materials are crushed to a powdery state and mixed with suspension of lime and a carbonate of ammonium then leave on air for fermentation. Approximately in three weeks, mix changes color from brown for bright blue. Mix is divided on a sieve. The received solution consists of an ortsein and directly litmus. Carry out spirit extraction as a result of which there is a pure litmus.
3. For the technical purposes when the experiment does not demand high precision, solution of litmus is prepared as follows. Litmus is dissolved in water therefore liquid has saturated blue color due to presence at it of carbonic alkali. After that solution is acidified sulfuric acid until litmus does not become violet color. The indicator is ready to use.
4. For receiving sensitive litmus solution is prepared in a different way. In the beginning litmus is extracted by usual alcohol then solution is removed. Add water to the rest and insist within a day. Then solution is evaporated on a water bath and add to it the absolute alcohol acidified by acetic acid. It is necessary to process litmus the acidified alcohol until solution does not cease to be painted. The powder processed thus is evaporated on a water bath with pure absolute alcohol again, and then dissolve it in water. Litmus is stored in low vessels. Densely it is not necessary to close a vessel, it is enough to cork a neck with cotton wool only.