Sodium formate: preparation and properties
Sodium formate is a compound representing an organic salt of formic acid. The chemical formula of the substance is HCOONa. The aggregate state is a crystalline powder of white or gray color, a greenish tint is less often observed. The substance is odorless, characterized by a moisture content of 3%.
Sodium formate is formed as a by-product during the synthesis of a tetrahydric alcohol – pentaerythritol. The direct preparation of the formic acid salt is carried out in several ways. All methods are based on the interaction of sodium hydroxide with one of the following compounds:
- Carbon monoxide. Reaction CO + NaOH = HCOONa. Absorption of carbon monoxide proceeds under a pressure of 6 – 8 bar and a temperature of 130 °C.
- Methyl formate. Process C2H4O2 + NaOH = HCOONa + CH3OH.
- Formic acid. Scheme HCOOH + NaOH = HCOONa + H2O. Neutralization of formic acid is carried out even in laboratory conditions.
- Chloral hydrate. Interaction C2H3Cl3O2 + NaOH = HCOONa + CHCl3 + H2O.
Finally, the formation of a formic acid salt also occurs during the reaction of chloroform with an alcoholic solution of sodium hydroxide.
Sodium formate is highly soluble only in water. It is slightly soluble in alcohol compounds and does not dissolve in ethers at all. Despite the fact that the substance is non-explosive and does not burn, smoking and keeping open flames near sodium formate is prohibited. The compound is classified as the most insignificant 4th hazard class. In fact, the substance is non-toxic and does not harm the environment.
One of the most common uses of sodium formate is construction. The compound serves as an antifreeze additive for monolithic and prefabricated concrete structures. There are a number of contraindications to the use of the substance. In particular, concrete with sodium formate is forbidden to use:
- in prestressed steel-reinforced structures (reinforcement classes AT-IV/V, A-IV/V);
- on concrete and reinforced concrete blocks operated in water and gas environments with air humidity over 60%;
- in reinforced concrete structures for electrified transport and industrial enterprises, where direct electric current is used.
The content of sodium formate in the concrete mixture is determined by the operating temperatures. With a design value of -5°C, 2% of dry powder by weight of cement is required. When hardening occurs at a temperature of -10°C, usually add 3%. Finally, at a value of -15°C, add 4%.
Another area of application is related to the fact that sodium formate acts as a corrosion inhibitor. Therefore, the substance is added to anti-icing bulk materials to reduce the negative impact on the metal parts of vehicles and other road facilities.
Additionally, sodium formate is used in areas that are listed below:
- in leather business – pre-tanning;
- medicine – reducing the level of toxic metabolites of ethanol;
- cosmetics – serves as a preservative;
- chemical industry – mainly for the production of formic and oxalic acids;
- electroplating – production of electrolytes.
Finally, sodium formate is used in the agricultural sector. The substance is added to agricultural feed to increase the level of digestibility. Less commonly, sodium formate is used for dyeing in the manufacture of fabrics and in printing.
Scope of sodium formate
Sodium formate is a salt of formic acid, which is formed as a crystalline powder, predominantly white in color. Less common gray and greenish tints. The substance is odorless. Among the basic areas of use of sodium formic acid are the chemical industry and construction. The compound has a melting point of 253°C, pH-pH=6. The density of sodium formate powder is 1.9 g/cc. The mass fraction of the substance in technical sodium formate is at least 92%, water – up to 3%, the rest is accounted for by impurities of pentaerythritol and its derivatives.
The cheapest way to produce sodium formate is associated with pentaerythritol. The formic acid salt is formed, as a by-product, by sodium ants during the synthesis of this tetrahydric alcohol. Alternatively, sodium formic acid is produced by direct chemical reactions between NaOH and other compounds:
- formic acid;
- carbon monoxide;
- chloral hydrate;
- methyl formate.
The listed methods require more costs and are less commonly used for the industrial production of sodium formate.
Areas of application
The application of sodium formate covers a variety of industries, including:
- jewelry business;
Also, sodium formic acid is used in housing and communal services. In particular, the substance is added to anti-icing reagents. Today, the emphasis is on the creation of materials with both high melting ability and low corrosivity. Both qualities are perfectly combined with sodium formate.
The substance is a corrosion inhibitor. At the same time, the melting power of the compound is 11.5 (at -5°C) and 5.7 (-10°C). At lower temperatures, the formic acid salt is ineffective. In terms of melting ability, formate is second only to sodium chloride and ammonium acetate. But the corrosivity of NaCl is 0.8 mg/cc per day. For formate, the same indicator is several times lower – 0.14. Superiority over ammonium acetate is associated with price. The cost of sodium formate is 3 times less.
Another popular use of formic acid salt is related to concrete and reinforced concrete structures. The key problem of construction at low temperatures is related to the cessation of hardening of sand-cement.
The problem is solved by adding antifreeze additives to concrete. The choice of sodium formate is caused by greater efficiency compared to other mineral components. At the same time, formic acid salt does not harm the environment. In concrete with sodium formate additives, efflorescence does not form on the surface.
The working mechanism is as follows. The addition of sodium formate affects the solubility of the silicate components of the cement. Accordingly, hydration is accelerated. The products of this reaction form salts with sodium formates, which leads to a decrease in the calculated curing temperature of concrete and an acceleration of the process itself.
Additives of sodium formate in concrete are necessarily made with plasticizers. This is caused by an increase in the volume of salts during crystallization. The process can lead to heterogeneity of the composition and degrade the quality of concrete. Addition of sodium formates with plasticizers:
- increases the mobility of the mixture;
- ensures uniformity by eliminating local stresses;
- reduces the water-cement ratio.
The size of the additive is determined by the operating temperature and is 2% (-5°C), 3% (-10°C) or 4% (-15°C) of the cement mass.
There are a number of situations where the use of sodium formate additives in construction is not recommended. These are reinforced concrete structures:
- under dynamic loads;
- reinforced with steel reinforcement, AT-IV/V, A-IV/V classes;
- with preliminary tension.
The use of sodium formate concrete should also be avoided in areas where humidity exceeds 60% and where there is no waterproofing. The last limitation affects reinforced concrete structures located near places where direct electric current is used. The last recommendation concerns the temperature of the liquid. Sodium formate is less soluble in cold water. Therefore, you need to add the composition to a warm liquid, but not higher than 70°C.
In the chemical industry, sodium formate is used as a reducing agent in organic synthesis. A characteristic feature of a compound in reactions is pH increase. Of the most common applications, one can single out the participation of formate in the production of formic and oxalic acids. Also, the substance is used in the manufacture of detergents.
You can buy sodium formate in pharmacies. The compound is sold (on its own or as part of other drugs) as a pharmaceutical drug with an action aimed at reducing the content of acetaldehyde in the body. This is a toxic substance formed in the liver from ethyl alcohol. Indications for the use of the drug:
- chronic alcoholism;
- withdrawal syndrome;
- alcohol intoxication.
Sodium formate is contraindicated in severe forms of diabetes mellitus and in persons with hypersensitivity to the drug.
In this area, the compound acts as a preservative and is labeled as E237. As a dietary supplement, sodium formate prevents the growth of bacteria and fungus. The compound has strong biocidal properties. But the antimicrobial effect of sodium formate is manifested only in an acidic environment. Permissible daily dose – 3 mg per 1 kilogram of weight.
Today, the E237 additive is prohibited in a number of countries, including the EU and the US. Gradually, the use of sodium formate in the food industry is declining. In particular, the substance is no longer used as a preservative in soft drinks and as a salt substitute for marinades.
In the leather industry, sodium formate is used as a tannin. Simultaneously, the compound helps reduce the acidity of the skin. Formate partially neutralizes the acid. Additionally, sodium formate increases the elasticity and strength of the product, increases their adhesive ability. Due to this, the substance has found a separate application in the production of rubber.
For the textile industry, sodium formic acid is used as a reducing agent, pickling agent, and also in the dyeing of fibers and fabrics. The last property of the formic acid salt is in demand in printing, wallpaper and paper production technologies.
Extraction and processing of oil
Salt of formic acid is used for anti-icing protection of industrial equipment. At the same time, formate serves as a component of drilling fluids. The introduction of sodium formate provides the following effects:
- stabilizes the temperature parameters of the composition;
- increases (correspondingly, makes heavier) the density of drilling fluids by 50%;
- reduces the rate of hydration of mixtures in wells, preventing freezing.
Additionally, sodium formate is contained in flushing cement slurries. The compositions are necessary for servicing wells.
Among the areas where sodium formate is also in demand, galvanization can be distinguished. The substance is used to regenerate the phosphate electrolyte of rhodium plating. At the same time, with the participation of a salt of formic acid, galvanic compositions for chemical nickel plating are prepared.
In agriculture, sodium formate acts as an additive in animal feed, increasing the digestibility of the product. In addition to improving feed conversion, the growth rate of animals increases, and the frequency of diarrhea decreases.