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Soda lime

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Chemical Components:
– Primary components of soda lime: calcium oxide (CaO), water (H2O), sodium hydroxide (NaOH), potassium hydroxide (KOH)
– Calcium oxide constitutes approximately 75% of soda lime
Water accounts for around 20% of soda lime
– Sodium hydroxide makes up about 3% of soda lime
– Potassium hydroxide is present at approximately 0.1% in soda lime

– Exhaled gases containing carbon dioxide pass through a soda lime canister in anaesthesia machines
– Medical-grade soda lime includes an indicating dye to show carbon dioxide absorption capacity
– Standard anesthesia machines typically contain up to 2 kilograms (4.4lb) of soda lime granules
– Recent carbon dioxide absorbents have been developed to minimize toxic by-product formation
– Absorbents like lithium hydroxide are used to reduce risks from inhaled anesthetics

Space Flight:
– Lithium hydroxide (LiOH) is used in space flights as a carbon dioxide absorbent
– Lithium hydroxide’s low molecular weight saves weight during launch
– During Apollo 13, spare absorbent cartridges were adapted to reduce high carbon dioxide levels
– The crew adapted the capsules for use in the Lunar Excursion Module (LEM) system
– Lithium hydroxide helps maintain safe carbon dioxide levels in confined spaces

Rebreather Use:
– Exhaled gas passes through a carbon dioxide scrubber in rebreathers
– Scrubbers are integrated into the breathing loop in rebreathers
– Fans are used in larger settings like submarines to ensure continuous gas flow
– Color indicating dye use in US Navy applications ceased in 1996 due to chemical release concerns
– Soda lime is crucial for removing carbon dioxide in rebreathers and closed-circuit diving systems

Chemical Reaction:
– The overall chemical reaction involves calcium hydroxide, carbon dioxide, and water
– Sodium hydroxide plays a catalytic role in the reaction system
– Moist sodium hydroxide on calcium hydroxide grains enhances reactivity
Water and moisture from respiration facilitate the reaction in soda lime
– Soda lime is used in closed-circuit diving rebreathers and anesthesia breathing circuits

Soda lime (Wikipedia)

Soda lime, a mixture of sodium hydroxide (NaOH) and calcium oxide (CaO), is used in granular form within recirculating breathing environments like general anesthesia and its breathing circuit, submarines, rebreathers, and hyperbaric chambers and underwater habitats. Its purpose is to eliminate carbon dioxide (CO
) from breathing gases, preventing carbon dioxide retention and, eventually, carbon dioxide poisoning. The creation of soda lime involves treating slaked lime with a concentrated sodium hydroxide solution.

Soda lime canister used in anaesthetic machines to act as a carbon dioxide scrubber.
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