Sodium silicate
| |
| Names | |
|---|---|
| IUPAC name
Sodium metasilicate
| |
| Other names
Liquid glass
Sodium polysilicate Sodium siliconate Waterglass | |
| Properties | |
| Na2SiO3 | |
| Molar mass | 122.062 g/mol |
| Appearance | White to greenish opaque crystals |
| Odor | Odorless |
| Density | 2.61 g/cm3 |
| Melting point | 1,088 °C (1,990 °F; 1,361 K) |
| Boiling point | Decomposes |
| 22.2 g/100 ml (25 °C) 160.6 g/100 ml (80 °C) | |
| Solubility | Reacts with HF Insoluble in organic solvents |
| Vapor pressure | ~0 mmHg |
| Thermochemistry | |
| Std molar
entropy (S |
113.71 J·K-1·mol-1 |
| Std enthalpy of
formation (ΔfH |
−1561.43 kJ/mol |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
| LD50 (Median dose)
|
1,153 mg/kg (rat, oral) |
| Related compounds | |
| Related compounds
|
Sodium hydroxide Silicon dioxide |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Sodium silicate, commonly known as water glass, is an ionic silicate of sodium. There are many compounds with the name "sodium silicate," but the most common is sodium metasilicate, Na2SiO3.
Contents
Properties
Chemical
Sodium silicate dissolves easily in water, forming a basic solution. It tends to form high hydrates, such as the pentahydrate and nonahydrate. Most metal salt solutions yield metal silicates upon treatment with sodium silicate, some similar in composition to silicate minerals. Sodium silicate can also act as a flocculating agent or to increase the viscosity of a liquid mixture, as well as a component in some cements.
Sodium silicate has the interesting property to decompose when treated with organic solvents such as ethanol and acetone. This results in formation of a resilient rubber-like gel, which is a form of silica gel. If this gel is dried and calcinated, very fine powders of SiO2 can be made. You can also sculpt small balls from this gel, which will solidify into hard marbles. Boiling chips can be made this way, since fully dried silica gel is very porous, which makes it prime boiling chip material.
Physical
Sodium silicate forms glassy, colorless crystals. It is slightly soluble in cold water (22.2 g/100 ml at 25°C), but more so in hot water. It is insoluble in alcohol.
Availability
Sodium silicate can be found at some chemical supply stores, though it may be easier to make it. In some countries, a concentrated solution of waterglass is sold very cheaply as an office glue. Waterglass can also be found in hardware stores as a cement mixing ingredient.
It is most of the time sold as solution.
Preparation
Sodium silicate can prepared by heating a sodium hydroxide solution with silica gel. A more dangerous method of preparation is to add plain glass scrap (not lead oxide glass or borosilicate glass) to molten sodium hydroxide. Rather than using glass, cleaned silica sand can be added instead. After thorough mixing of the silica into the sodium hydroxide(an excess of the silica is required to prevent sodium hydroxide in the product), the mass of reactants hardens, and can be leached with warm water to obtain a viscous solution of sodium silicate.
Projects
- Making a chemical garden
- Egg preservation
- Making silica gel
- Purifying silicon dioxide
Handling
Safety
Sodium silicate is not particularly toxic, though it may contain free alkali and gloves should be worn when handling the protection.
Storage
Solid sodium silicate can be stored in closed containers. Silicate solutions should be stored at temperatures lower than 60°C, as higher temperatures tend to promote dehydration of the silicate, causing a surface skin to be formed.[1]
Disposal
Sodium silicate can be neutralized with an acid and since the byproducts are not toxic, they can be safely disposed of.
