Sodium silicate, commonly known as “water glass” or “liquid glass,” is an inorganic compound derived from silica, sodium oxide, and water. It is supplied either as a viscous, syrupy liquid or as a solid, glassy powder or flakes. While it is not considered inherently toxic, concentrated forms are highly alkaline and corrosive, which is the primary source of its danger. Therefore, its hazard level depends almost entirely on its concentration and physical state.
Common Applications and Exposure Routes
The general public encounters sodium silicate in a variety of products. In the construction industry, it is widely used as a hardening agent for concrete and cement, as well as a liquid sealant for waterproofing masonry. Its strong adhesive properties make it a component in various glues, especially for bonding paper and cardboard in manufacturing.
In the home, people may handle it as a component in specialized automotive repair kits, where it is used to seal leaks in head gaskets and exhaust systems due to its ability to withstand high temperatures. It also plays a role in the water treatment industry and is added to some powdered laundry and dish detergents, where its alkalinity helps in cleaning and corrosion inhibition.
Potential exposure routes for individuals depend on the application, ranging from dermal contact with household sealants to inhalation of fine dust or mists in industrial settings. Industrial workers face exposure through its use in drilling fluids for stabilizing borehole walls and in the manufacture of refractory ceramics. The risk is significantly higher when handling the concentrated liquid form or the powdered solid, rather than the trace amounts found in consumer goods.
Understanding Acute Toxicity and Health Effects
The toxicity of sodium silicate is a direct consequence of its high alkalinity, meaning it has a high pH, which is corrosive to biological tissues. When concentrated solutions contact the skin, they act as strong alkaline irritants, capable of causing severe redness, pain, and chemical burns depending on the duration of exposure. Contact with the eyes poses a serious risk, as the high pH solution can cause immediate, severe irritation and potentially permanent eye damage.
If the powdered form is inhaled, it acts as a respiratory tract irritant, causing a burning sensation in the throat and lungs. Symptoms may include coughing, wheezing, and shortness of breath, and exposure to high concentrations of mist or dust can lead to lung damage. It is important to note that sodium silicate is an amorphous form of silica and does not pose the same long-term risk of silicosis associated with crystalline silica dust.
Accidental ingestion of a concentrated solution is a medical emergency because the alkaline nature of the compound causes corrosive burns throughout the gastrointestinal tract. This can damage the lips, mouth, esophagus, and stomach lining, leading to symptoms like nausea, vomiting, and severe irritation. The extent of the damage is dependent on the concentration of the sodium silicate solution ingested.
Safe Handling and Emergency Response
Given the corrosive nature of concentrated sodium silicate, cautious handling is necessary to prevent accidental exposure. When working with the liquid or powder, individuals should wear personal protective equipment, including chemical-resistant gloves and safety goggles or a full face shield to protect the eyes. Working in a well-ventilated area is also important to minimize the inhalation of dust or mists.
Proper storage is a key safety measure, as sodium silicate should be isolated from incompatible materials, especially strong acids, which can cause a hazardous gelling reaction. The substance is recognized by regulatory bodies as a hazardous material, and it is classified for transport as a corrosive basic liquid.
In the event of skin contact, the affected area must be immediately flushed with running water for at least 15 to 20 minutes while contaminated clothing is removed. For eye contact, immediate and prolonged rinsing with water for at least 15 minutes is necessary, and medical attention should be sought immediately. If accidental ingestion occurs, vomiting should not be induced; instead, the person should drink large quantities of water or milk and receive immediate medical assistance.