Soda lime

File:Drägersorb Soda Lime.jpg

Soda lime granules used in medical applications.

Soda lime is a mixture of chemicals, primarily consisting of calcium hydroxide, used in various applications, including anesthesia, oxygen therapy, and rebreather systems. It is known for its ability to absorb carbon dioxide (CO_) from exhaled gases, making it an essential component in closed-circuit breathing systems.

Composition

Soda lime is composed mainly of calcium hydroxide (Ca(OH)_), with smaller amounts of sodium hydroxide (NaOH) and potassium hydroxide (KOH). These hydroxides react with carbon dioxide to form calcium carbonate (CaCO_), water (H_O), and heat. The typical composition of soda lime is approximately 75% calcium hydroxide, 3% sodium hydroxide, and 1% potassium hydroxide, with the remainder being water and other inert materials.

Chemical Reaction

The primary reaction of soda lime with carbon dioxide can be represented as follows:

CO_ + Ca(OH)_ _ CaCO_ + H_O

This reaction is exothermic, meaning it releases heat. The efficiency of soda lime in absorbing CO_ is influenced by factors such as granule size, moisture content, and the presence of catalysts.

Applications

Medical Use

In the medical field, soda lime is used in anesthesia machines to remove carbon dioxide from the breathing circuit. This is crucial in maintaining a safe and effective anesthetic environment for patients undergoing surgery. The use of soda lime in anesthesia allows for the recycling of exhaled gases, reducing the need for fresh gas flow and minimizing environmental impact.

Diving

Soda lime is also used in rebreather systems for diving. In these systems, the diver's exhaled breath is passed through a canister containing soda lime, which absorbs the carbon dioxide, allowing the remaining oxygen to be rebreathed. This process extends the duration of the dive and reduces the amount of gas the diver needs to carry.

Safety Considerations

While soda lime is effective in absorbing carbon dioxide, it must be handled with care. The reaction with CO_ is exothermic, and improper handling can lead to overheating. Additionally, soda lime can become caustic if it dries out, posing a risk of chemical burns. It is important to store soda lime in airtight containers to maintain its moisture content and effectiveness.

Related Pages

• Calcium hydroxide
• Anesthesia
• Rebreather
• Carbon dioxide