خصائص بعض القلويات الكثيرة التداول في تركيب محاليل الاظهار ..التحميض والطبع والتكبير

Characteristics of some widely circulated alkalis in the composition of show solutions:
Sodium carbonate
It is the most common alkali in the composition of highlighting solutions, and it is usually found in the markets in one of the following three forms.

A - Sodium carbonate (crystal)
It is a salt that contains a large proportion of water and therefore is in a crystalline form. The crystals hold only approximately 37% by weight of pure powdered sodium carbonate. Therefore, it is possible, in the installation of highlighting solutions, to replace each. 100 grams of sodium carbonate (crystalline) by adding only 37 grams. powdered sodium carbonate.

b - sodium carbonate (anhydrous-desiccated powder)

Theoretically, this salt should be completely water-free, but it usually holds about 2% of its weight in water, and the rest is pure salt. It is possible to replace every hundred grams of this salt with the equivalent of 110 grams of potassium carbonate.

C - Sodium Carbonate Monohydrate

It contains about 85% of its weight of powdered sodium carbonate and the rest of the water. The following table shows the quantities of sodium carbonate salts. In its different forms that can be replaced by another quantity of the same salt in another form:
Sodium carbonate is a salt that dissolves quickly in water at high temperatures. Its powder has the ability to absorb water vapor if left for a long time in the air. Therefore, it must always be kept in tightly sealed bottles with a cork cover (because the glass cover sticks to the mouth of the glassware) or a cork covered with tarpaulin. Salt prepared for commercial purposes is often mixed with impurities from other salts (such as sodium chloride or sulfate), so it is always better to buy it from trusted photocopy shops. Due to the high alkalinity of the sodium carbonate solution, it is widely used as an active alkaline substance in the show solution.

2- Potassium carbonate:

It is usually found in the form of an anhydrous salt. If it crystallizes for any reason, it is easy to turn it into a powder by heating. First, it turns into a cohesive mass, then it disintegrates when it absorbs water vapor, and then it finally turns into water and energy mixed in front of a powder by heating.
This substance should also be preserved in glass containers that have a cover made of rubber or cork covered with linoleum (the same reason mentioned above for sodium carbonate). And due to the possibility of mixing it with impurities (chloride or sulfate), therefore, the negative atmosphere should be verified for its purity upon purchase, and since its solution has a high degree of alkalinity, so it can be used as an activating agent in the display solution, but it is criticized for the possible staining of negative images.
It is possible to replace each gram of potassium carbonate with the equivalent of 1 gram of powdered sodium carbonate. Potassium carbonate has no advantage over sodium carbonate except in the case of preparing concentrated solutions only, as its solubility in water is greater than that of sodium carbonate.
3_ caustic alkali:
Caustic potash, sometimes called potassium hydroxide, is included under this designation. Hydroxide and caustic soda, sometimes known as Sodium Hydroxide, which are white caustic substances with a soapy texture, can be obtained in the form of small sticks. Because of its strong ability to liquefy, it must be kept in glass containers tightly sealed with a cork lid, otherwise it absorbs water vapor and carbon dioxide gas.

It is possible to replace each gram of caustic soda with the equivalent of 1 gram of potassium hydroxide. Caustic soda is easily soluble in water, and with its solubility, thermal energy is released that raises the temperature of the water. Its solution is very alkaline, so it is used if a strong activating agent is to be added to the show solution.

Show solutions that contain caustic alkalis do not have any ability to survive for a long time, rather they deteriorate quickly, unlike solutions in which carbonates are used. Caution should be exercised when using them, as they cause severe infections on the human skin, also cause serious damage to the eyes, and have a severe and damaging effect on both organic and inorganic materials, and increase the swelling of the sensitive gelatin layer.

4_ Borax:

Sometimes known as Sodium Triborate, it may be found in the form of a white powder or in the form of small, colorless crystals that dissolve easily in water. The degree of alkalinity of the borax solution is lower than that of the aforementioned salt solutions, and therefore it is considered a salt with limited activity in the show solution, and borax is often used Exposure solutions that lead to fine grain developers. In contrast to the previously mentioned alkaline salts, it is not customary to replace borax with another salt (such as sodium carbonate, for example).

5- Kodalk:

It is an alkaline salt produced by Kodak factories and is sometimes known as Kodak Balanced Alkali. Its alkaline degree is higher than borax salt, and less than sodium carbonate salt. It is possible to replace the skodalic salt in the composition of solutions, otherwise in the name of showing, by adding half of its quantity of sodium carbonate (S-kodalak = S-sodium carbonate).
Kodalak salt is distinguished from carbonates in that it does not cause gases to be emitted when treating the film in the stop or acid fixation solution, unlike sodium carbonate, which releases carbon dioxide gas when mixed with acid solutions, in addition to the possibility of salt deposits forming on the surface of the film, such as aluminum carbonate. Aluminum carbonate resulting from the interaction of sodium carbonate with acid fixing & Hardner solutions that increase the hardness of gelatin, which carries within its components Alum-like substance in addition to other acidic solutions such as acetic acid.

6 - Sodium metaborate. Metaborate

And it shares with the substance scodalak in the previous feature another alkaline salt, which is meta borate, which has not been synthesized by the sodium fractions, which can be installed by adding one part of sodium hydroxide in a thinner (pure caustic soda) to five parts of borax.