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FAQ

Below you will find the most frequently asked questions about sodium silicate, its usefulness, costs, experiments etc., for more information contact us

Are all silicates soluble?

No. Only silicates of the elements from the first group of the periodic table (lithium, sodium, potassium, rubidium, cesium, francium) and the ones of quaternary ammonium are soluble in an aqueous environment; all other metals form insoluble silicates. This is of fundamental importance for the use of sodium silicate as inertizing agent of waste, toxic and harmful substances; in fact it’s possible to mix an aqueous solution of sodium silicate with materials containing heavy metals ions, hazardous for living organisms’ health, which react with silica becoming insoluble and returning to their natural shape of mineral silicates, stable and not hazardous.

Can Sodium Silicate in solution be used to waterproof concrete structures?

Yes. Certain types of sodium silicates in solution and derivatives thereof are being used for a long time as impregnating agentes for already hardened cement. It can be applied by spraying or by dipping on the surface of the cement structure (wall or flooring), going on sprinkling the surface until rejection; the existing excess can be washed out with running water. After this treatment the cement shows minimum or zero porosity, greater resistance to abrasion, to erosion and to freeze-thaw phenomenon, to the acid aggression or to the penetration of the deleterious ions such as chlorides and sulphates, managing this way to protect the metal framework from corrosion. For further details contact the technical service of INGESSIL S.r.l.

Can Sodium Silicate in solution be used for potable water?

Yes. Thanks to their lack of toxicity, specific types of sodium silicate solutions can be added, in terms of part per million, to potable water to avoid corrosion of the metallic pipes that it could cause by flowing in them. In fact sodium silicate act as an anticorrosive by binding to the walls of the pipelines and creating a monomolecular protective film impervious to oxygen and to acids. It is also desirable the presence of silica dissolved in potable water, since it ensures the absence of aluminium that is a toxic element for living organisms. Silica and alumina are indeed incompatible compounds in solution because they make each other insoluble; so the presence in the solution of one of them guarantees the absence of the other one. It is a procedure that is currently adopted in several aqueducts, maintaining the organoleptic qualities of water unaltered.

Is it a caustic alkaline?

Commercial solutions of sodium silicate show a pH between 10,5 and 13. This values depends on the type of sodium silicate and its concentration, characterizing it as alkaline substance which, in the extreme case of pH 13, is labelled as “irritant” or “corrosive” to eyes depending on the moral ratio and on the concentration . Therefore skin contact shall be avoided by using proper protection, such as coveralls and gloves, providing besides constant protection to the eyes by using safety glasses and a device suited for eye wash in case of accidental contact (see answer to question number 2). Sodium silicate in solution shows anyway pH values way lower than the ones that characterize many commonly used substances, such as cement pastes that have a pH of about 12,5, or as caustic soda that has a pH close to 14 even diluted to 4% in water.

In which type of packaging is Sodium Silicate sold?

According to the customer needs, INGESSIL S.r.l. provides its products in 1000 litres plastic tanks with a drain valve at the bottom, in 30 ton tankers or in 60 ton road tanker. Given the decades-old expertise in the field, INGESSIL S.r.l. is available to suggest the possibilities of storage at the customers’ himself. For specific types of products there is the chance of providing the product in 200 litres iron drums. Whenever you wish for detailed information on the subject, you are invited to contact the technical service of INGESSIL S.r.l.

How can I dispose of Sodium Silicate in solution surplus?

According to current italian regulations, as explained in point 13 of every safety data sheet too, the material can be disposed of as special waste after bringing its pH under a value of 9,5. For specific information regarding the neutralization’s modes of the product you are invited to contact the technical service of INGESSIL S.r.l.

Why isn’t it used for the preservation of eggs?

In the past particular types of sodium silicate solutions were used to preserve the qualities of fresh eggs over time. Eggs were immersed in a basin containing sodium silicate and, after being properly washed with tepid water, they could be eaten a year later still as good as freshly taken from the henhouse. This is possible thanks to the aseptic environment, guaranteed by the sodium silicate basicity, and by the fact that immersed in the liquid, the egg isn’t subjected to drying, thus inside the egg the characteristic air chamber of old eggs isn’t formed. By the introduction of low-cost fridges on the market this application has started to fade but it is still the most efficient method to preserve eggs (even if less practical).

Can Sodium Silicate be added to cement?

Sodium silicate is a cement set accelerator. An addition of 10% of sodium silicate to cement cause its instant set. Among the many additives proposed, sodium silicate is the only one that doesn’t upset the cement nature, which is a silicate itself. In the cement the major component is tricalcium silicate (so called because it is composed of 3 moles of CaO and 1 of SiO2), highly basic because the base (3 moles of CaO) predominate over the acid (1 mole of SiO2); in sodium silicate the base (1 mole of Na2O) is in deficit compared to the acid (3.5 moles of SiO2). The addiction of sodium silicate to cement raise the content of SiO2, buffering its excessive basicity, improving its characteristics, as long as the ratio cement/water remains unaltered. To achieve this last condition the quantity of water injected with sodium silicate must be subtracted from the paste water. The other accelerators, such as sulphate aluminium (called alkali free), upset the cement nature, transforming tricalcium silicate into sulphate calcium (chalk) expansive and soluble in water.

Does it tend to re-dissolve in water, once dried?

Sodium silicate in solution loses, by evaporation at temperatures lower than 120°C, solvent water, creating so a vitreous substance composed of hydrated sodium silicate, namely still with some chemically linked water molecules. This substance is fireproof and it has excellent rigidity- and heat resistance characteristics. As explained in the answer to question n.8, this material re-dissolve in water, the slower the lower the temperature of this last is. For particular types of application it is possible, using strict procedures, to fully dehydrate sodium silicate and to make it this way indissoluble in water by indefinitely heating at temperatures higher than 600°C. For detailed information and specific case evaluations, you are invited to contact the technical service of INGESSIL S.r.l.

Which products have to be used to remove possible incrustation?

Sodium silicate in glassy state, like it presents itself after the evaporation of solvent water, it is still soluble in water. The less water is contained in the dried material, the lower is the tendency to get back in solution, therefore the formation of incrustation can be prevented by washing immediately after the use of machineries with warm or tepid water. Already formed incrustations can be removed by leaving them in warm water. Whenever there are particularly dried incrustations, you can have recourse to water containing caustic soda, unless stated contraindications for the use of this last. You mustn’t have recourse to commonly used solvents of organic nature, such as alcohol or acetone, since they are incompatible with sodium silicate nature.

Heating up aqueous solution of sodium silicate are toxic substances released?

Absolutely not. By heating they only release water vapor, while the solution of sodium silicate progressively concentrates itself increasing its viscosity rapidly. Precisely for the efficiency and security of this procedure, solutions of sodium silicate are used as bonding agent for paper, cardboard, cork, metals and rock or glass wool, particle and inorganic material in general. Sodium silicate is the only bonding agent resistant to high temperatures, until 1000°C. Whenever these solutions come into contact with incandescent surfaces, the formation of a sodium silicate aerosol is to be expected; in this case the directions given in question n. 4 are still valid.

How long is Sodium Silicate stable in solution?

Sodium silicate in aqueous solution is a stable product and doesn’t alter its physico-chemical characteristics over time, as long as it is preserved in a suitable and tightly closed container. It is recommended to store the product in iron-steel- or plastic containers, avoiding polyester resin materials and amphoteric metals tanks, such as zinc, aluminium or their alloys. In order to not alter their characteristics, sodium silicate in aqueous solution mustn’t come in contact with organic reagents, acids. In literature (2) an episode in which a sodium silicate solution handed down from a grandfather to his grandson has preserved its characteristics unaltered for over half a century is reported.

If ingested, is Sodium Silicate lethal?

As every substance, sodium silicate can be tolerated from the organism up to a certain limit. To define this limit we resort to an index, the LD50, namely the Lethal Dose that causes the death of 50% of the lab rats to which it is injected in one dose. This limit changes depending on the type of the commercial solution of sodium silicate taken into account, but even in the most unfavourable chance it turns out to be higher than 1.5 per Kg of the subject’s body mass. In other terms, a person of about 70 Kg should ingest at least 100 g of a commercial solution of this product to have the 50% chance of death. But bear in mind that sodium silicate is an alkaline solution, irritant for the mucosae and so difficult to ingest in large quantities accidentally; moreover a rapid medical treatment could greatly limit the chance that it turns out to be lethal. Make the injured person drink first a quantity of water equal to 5 or 10 times the weight of the silicate ingested and then vinegar or lemon juice in a double amount compared to the sodium silicate ingested, would be enough. This way the formation of silica gel precipitates is avoided, which would block the digestive tract, and the sodium silicate basicity is neutralized, to which its low hazard is linked.

If inhaled, does Sodium Silicate cause silicosis?

Silicosis (or pneumoconiosis) is a serious occupational illness caused by the inhalation of particles constituted by crystalline silica (SiO2), which causes the hardening of the tissues and loss of lung capacity, often with fatal outcome. Sodium silicate doesn’t cause silicosis. By heating, solutions of sodium silicate only release water vapor and, whenever an aerosol of sodium silicate is inhaled, being it water-soluble, it is rapidly blocked by nasal- and upper respiratory tract mucosae and expelled through sneezing. The fraction that possibly could reach the lungs would be absorbed in the bloodstream and expelled through urine. This way, even if it could cause temporary irritation of respiratory tracts, it can’t lead to the development of pathologies such as silicosis.

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