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Caustic Soda – Sodium Hydroxide Uses, Warnings & Safety
Caustic soda – or sodium hydroxide – is a strongly basic substance used in many areas.
Caustic soda is commercially available in solid form, but also in the form of solutions at different concentrations. It is a reagent widely exploited both at an industrial and domestic level, as it is widely used in various types of research laboratories (chemical laboratories, chemical-pharmaceutical laboratories, etc.).
Although it can also be purchased by private individuals for domestic use, due to its danger, the use of caustic soda requires special precautions and knowledge.
Did you know that:
The term “caustic” comes from the Greek ?a?st???? (kaustikòs) which literally means “burning”.
What is caustic soda?
Caustic soda is the common name that indicates the chemical compound having the brute formula NaOH . This compound, more correctly called “sodium hydroxide “, is a strong base which – as can be easily deduced from its name – is capable of exerting a strong caustic action when it comes into contact with certain living materials and tissues.
In some cases, caustic soda is also incorrectly defined as “sodium hydrate”, “sodium hydrate” or “sodium hydrate”.
Caustic soda should not be confused with ” soda “, a common name with which you want to indicate a completely different chemical compound, ie sodium carbonate (Na2CO3). In fact, the latter compound is the sodium salt of carbonic acid and not a strong base like sodium hydroxide.
What are the main characteristics of caustic soda?
Caustic soda is a solid compound at room temperature, but highly hygroscopic (i.e. it is able to absorb the humidity contained in the air) and, consequently, deliquescent.
In other words, due to its remarkable ability to absorb humidity present in the air (hygroscopic properties), caustic soda changes its physical state from usually to liquid (deliquescence phenomenon).
However, caustic soda looks like a white odorless solid. Normally, in the solid-state, it is found in the form of flakes or pearls.
Another characteristic of caustic soda is that of producing heat when placed in water. In fact, the dissolution of sodium hydroxide in water is highly exothermic, so much so that the temperature reached during this operation can even exceed 95 ° C. Caustic soda solutions are generally colorless, clear or sometimes slightly turbid and, depending on the amount of sodium hydroxide they contain, have a more or less basic pH.
Caustic soda is not only soluble in water, but also in ethanol (or ethyl alcohol, if you like). The dissolution of caustic soda in ethanol is even more dangerous than that in water, this because the strong heat that is released during the dissolution of the substance can even make the vapors of ethyl alcohol ignite (remember, in fact, that ethanol is a very volatile substance).
What are the uses of caustic soda?
As mentioned, caustic soda is a compound used both at an industrial and domestic level and can be used in many areas, from cooking to cosmetics.
In the industrial field, caustic soda is used as a reagent in numerous chemical reactions, but it can also be used in the form of an additive. In detail, caustic soda is used:
- To synthesize paints and dyes ;
- For the synthesis of sodium hypochlorite, the main component of the well-known bleach;
- For the regeneration of the resins to ion exchange (special resins used in demineralization processes and purification of ion-exchange water);
- To carry out the saponification reaction, so for the production of some types of soap (eg Marseille soap, Aleppo soap, etc.).
- In the food industry, where it is used as an acidity regulator and as a synthetic technological adjuvant. In this context, caustic soda is used, for example, for the industrial preparation of caramel and pretzels, to de-bitter olives and as a food additive in snacks, jellies, and desserts. Caustic soda used as a food additive is indicated on the label with the initials E524.
- In the wine industry, where it is used in the form of tank cleaning solutions.
- In the cosmetic industry, where it is used as a pH regulating agent. In this context, caustic soda is used, for example, in beard products, hair removal products, and various detergents. Usually, in the list of ingredients shown on cosmetic products, caustic soda is indicated by the name “Sodium Hydroxide”.
- In the chemical-pharmaceutical industry, as a pH regulator.
- In the electronics and electrical engineering industry for the production of circuits.
Caustic soda is also used in the home, especially for unclogging sinks, showers, tubs, toilets, etc., therefore, for unclogging domestic drains. However, this practice is not highly recommended, both because of the danger deriving from handling caustic soda and because – if not properly diluted – sodium hydroxide could damage the pipes.
However, in addition to this type of use, caustic soda can also be used in the home for:
- Cleaning grills and barbecues;
- Clean the tanks used in the artisanal production of wine;
- Stripping the wood;
- Making artisan soap, using it to saponify various types of vegetable oils and fats.
Although caustic soda can also be sold to private individuals and can be used in the aforementioned domestic activities, we remind you again that the use of this substance entails a series of potential risks and that, therefore, it must be carried out with extreme caution and with all precautions of the case.
How is caustic soda disposed of?
Caustic soda and its solutions must not be disposed of in the sewers or in the environment but must be disposed of according to the regulations in force in specifically authorized waste collection points.
In case of doubt, therefore, it is necessary to contact the service provider for waste management in your area, or contact companies specializing in the disposal of similar chemical products.
Warnings and Safety
The companies producing caustic soda, together with the product, must provide a safety data sheet (SDS) that contains the warnings and all information on the chemical-physical, toxicological and environmental hazard properties of the chemical produced. This information is necessary to be able to handle and use caustic soda correctly and safely.
Among the various data in the safety data sheet which must also be present on the label, we mention the risk phrases and the classification of the product according to the EC regulation 1272/2008.
In the specific case of caustic soda, the risk phrase reported is ” R35: Causes severe burns ” and the substance is classified as ” Corrosive ” and accompanied by the corresponding hazard pictogram (see figure).
This pictogram indicates that the chemical compound in question – therefore, in this specific situation, caustic soda – can be corrosive to metals and causes serious skin burns and serious eye injuries.
In addition to the aforementioned information, the safety data sheet must also contain information on the manufacturing company, information concerning product handling and storage, information on first aid measures, on fire prevention measures and on the measures to be taken in case of environmental release and information related to the transportation and disposal of the product.
Precautions for use
What precautions should be taken before using caustic soda?
- Given the dangerous nature of the product, it is essential to take precautions and precautions before and during the use of caustic soda.
- Following are some indications on the precautions and preventive measures that must be taken before and during the handling of sodium hydroxide:
- Avoid direct contact with caustic soda and always wear suitable protective clothing (gloves, goggles, mask, lab coat, long sleeve shirts, closed shoes, and long pants);
- When preparing a caustic soda solution, gradually add small quantities of sodium hydroxide to the water and NOT vice versa. The highly exothermic reaction between caustic soda and water would be excessively violent if the procedure were carried out in the opposite direction, that is, if water was added to the caustic soda. To optimize the dissolution process, it is also advisable to place the container in which the solution is prepared in a water and ice bath.
- Store caustic soda tightly closed in a cool dry place.
- Avoid contact with metals such as zinc, tin, and aluminum, as caustic soda is corrosive to these substances, especially when in the presence of humidity.
- Beware of contact with ammonium salts (since caustic soda reacts with these compounds to release ammonia), with acids (exothermic reaction) and with metals (release of hydrogen).
First Aid Tips
What to do in case of contact with caustic soda?
Given the high basicity and the consequent high corrosive power of caustic soda, in case of contact with eyes, skin or mucous membranes, in case of inhalation and / or in case of ingestion, it is necessary to immediately call medical help and go to the nearest first aid.
Pending the arrival of the emergency medical personnel or the doctor, however, some operations must be carried out in order to remove the caustic soda coming into contact with it from the body. Therefore, here below you will find some useful first aid advice to put into practice in case of accidents with caustic soda.
- In the case of caustic soda contact with clothes, remove them immediately, and wash the body with plenty of water. Of course, before any reuse, clothing that has come into contact with caustic soda must be washed.
- In case of contact with skin, wash immediately with plenty of soap and water, rinse carefully.
- In case of contact with the eyes, wash immediately with plenty of running water keeping the eyelid open (in the laboratories and in the industries there are special emergency eyewashes for this kind of situation).
- If swallowed, rinse mouth immediately with water, but DO NOT induce vomiting.
Regardless of the type of contact with caustic soda (with clothes, with the skin, with mucous membranes, etc.), the speed of intervention is fundamental in order to limit the damage; just as it is essential to immediately contact the doctor or the emergency room immediately after putting the above first aid tips into practice.