Javel water as a bleaching agent. simple recipes

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Javel water as a bleaching agent. Simple recipes and tips

Factory technologies - simple recipes

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Among fabric bleaches, one of the main places is occupied by bleach and sap water. In order to understand the processes that occur during bleaching with bleach, chlorine and hypochlorous salts and acid, we first present some information from chemistry regarding bleach.

Regular commercial bleach consists, depending on the method of preparation, of mixed calcium salt, hypochlorous and hydrochloric acids with an admixture of slaked lime, or only of the above compound. In the first case, the content of active chlorine is 25-36%, in the second case - about 50%. When air is introduced, chlorine is released from dry bleach, and hypochlorous acid is released from wet bleach. Due to the changing composition, the quality of bleach is determined by the percentage of active chlorine. Bleach should be stored in a cool, dark place and in a container that is not too tightly sealed.

It has been established that an aqueous solution of bleach, after standing for some time, contains calcium hypochlorite salt Ca(OCl)2 and calcium chloride CaCl2,

To obtain a bleach solution, bleach is first ground with water into a thick, lump-free dough, and then water is added. If soda or Glauber's salt is added to this solution, then calcium in the first case will be released from the solution in the form of a precipitate of calcium carbonate salt (chalk), in the second case - in the form of calcium sulfur salt. The sediment is allowed to settle for several days. The transparent greenish solution will be a solution of sodium chloride salt (with an admixture of table salt and sodium hydroxide). Practically, precipitation is carried out in a wooden vat with several taps or stoppers located at different heights.

After draining the bleaching liquid, the remaining sediment can be used as a disinfectant for latrines, etc. According to Gager, the following quantities of components are used to obtain bleaching liquid: 800 g of bleach with 25% active chlorine content is ground with 16 liters of cold water: to The resulting mixture is poured with a solution of 1 kg of crystalline soda in 8 liters of water. After stirring, the composition is allowed to settle quietly and the clear liquid, which is javelle water, is decanted.

Properly prepared Javel water has the following advantages over other bleaching agents for fabrics (linen):

When using Javel water, oxycellulose is not formed, leading to tissue destruction, as is the case when using oxygen bleaching agents.

It is not chlorine that reacts, but the more harmless hypochlorous acid.

After bleaching, the bleaching liquid can be completely removed or neutralized (by washing with water and a weak solution of sulfide-sodium salt - hyposulfite.)

When bleaching linen, neither calcium soaps nor calcium carbonate salts are deposited on the fibers, which can occur with the direct use of bleach.

The bleaching principle of javele water is, on the one hand, free chlorine, and on the other hand, hypochlorous acid. The formation of chlorine or hypochlorous acid depends on external conditions and can be arbitrarily regulated. Hypochlorous acid is a more valuable and active bleaching agent, as a result of which it is necessary to strive to ensure that the decomposition of Javel water during bleaching occurs with the formation of hypochlorous acid, and not chlorine, which has a harmful effect on the fabric.

When hydrochloric, sulfuric or oxalic acids are added, chlorine is released. If free carbon dioxide acts on hypochlorous sodium salt, then hypochlorous acid is released.

During the bleaching process, hypochlorous acid decomposes into oxygen (O2) and hydrochloric acid (HCl). Oxygen, at the moment of release, oxidizes colored compounds, turning them colorless. Thus, bleaching is reduced to the oxidative effect of oxygen, which at the moment of release is highly active.

The resulting hydrochloric acid reacts with soda or sodium acetate and produces sodium chloride and free acetic acid or carbon dioxide. These latter again decompose the hypochlorous sodium salt according to the above reactions, so that this process occurs automatically until the entire amount of hypochlorous sodium salt is exhausted, and the amount of acetic acid or carbon dioxide can be very insignificant.

As for the content of some caustic soda in the bleaching liquid, it is useful to neutralize it with acid. Since chlorine has a harmful effect on fabrics, it is removed using the so-called antichlorine - sodium sulfide salt (hyposulfite).

The process of bleaching fabric or linen is carried out in practice as follows.

500-750 cm3 of bleaching liquid is diluted in 10 liters of cold water and the washed fabric is immersed there for 10-15 minutes. If you leave the fabric in the bleaching liquid overnight, then it is enough to take 100 liters of bleaching water per 0,25 liters of water. Add about one teaspoon of vinegar to the bleach bath. You need to make sure that the water is cold and the fabric is completely immersed in the liquid. Metal parts - buttons, hooks, etc. must be removed first. Utensils should be made of wood or well-enameled. After the specified time has elapsed, the fabric is removed, washed in clean running water and then dipped into an antichlorine (hyposulfite) solution to remove chlorine. For 10 g of water, 3% antichlor is sufficient, which is advisable to first dissolve in a small amount of water, and then add to the rest of the water while stirring. After 15-30 minutes, rinse well, and it is recommended to add a small amount of ammonia to the first portions of rinse water.

Author: Korolev V.A.

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