Soda lime - wikipedia Soda lime Drägersorb ® Soda Lime Soda lime is a mixture of chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent CO retention and carbon dioxide poisoning. It is made by treating slaked lime with concentrated sodium hydroxide solution. Contents 1 Chemical components 2 Anaesthetic use 3 Rebreather use 4 Chemical reaction 5 Analogy with the alkali - silica reaction 6 See also 7 References 8 External links Chemical components The main components of soda lime are Calcium hydroxide, Ca ( OH ) ( about 75 % ) Water, H O ( about 20 % ) Sodium hydroxide, NaOH ( about 3 % ) Potassium hydroxide, KOH ( about 1 % ). Anaesthetic use During the administration of general anaesthesia, the gases expired by a patient, which contain carbon dioxide, are passed through an anaesthetic machine breathing circuit filled with soda lime granules. Medical - grade soda lime includes an indicating dye that changes color when the soda lime reaches its carbon dioxide absorbing capacity. To ensure that a soda lime canister ( CO absorber ) is functioning properly, it should not be used if the indicating dye is activated. Standard anaesthesia machines typically contain up to 2 kg of soda lime granules. Lithium hydroxide ( LiOH ) is the alkali hydroxide with the lowest molecular weight ( 24 g / mol ; Li : 7 g / mol ) and is therefore used as CO absorbent in space flights since the Apollo programme to spare weight at launch. During Apollo 13 flight, the crew sheltered in the lunar module started suffering from high CO levels and had to adapt spare absorbent cartridges from the Apollo capsule to the LEM system. Recent generation of CO absorbents have been developed to reduce the risk of formation of toxic by - products as a result of the interaction between the absorbent and inhaled anesthetics. Some absorbents made from lithium hydroxide ( LiOH ) are also available for this purpose. Rebreather use Exhaled gas must be passed through a `` carbon dioxide scrubber '' where the carbon dioxide is absorbed before the gas is made available to be breathed again. In rebreathers the scrubber is a part of the breathing loop. Color indicating dye was removed from US Navy fleet use in 1996 when it was suspected of releasing chemicals into the circuit. In larger environments, such as recompression chambers or submarines, a fan is used to maintain the flow of gas through the scrubbing canister. Chemical reaction The overall reaction is : CO + Ca ( OH ) → CaCO + H O + heat ( in the presence of water ) Each mole of CO ( 44 g ) reacting with calcium hydroxide produces one mole of water ( 18 g ). The reaction can be considered as a strong - base - catalysed, water - facilitated reaction. The reaction mechanism of carbon dioxide with soda lime can be decomposed in three elementary steps : 1 ) CO → CO ( CO dissolves in water - slow and rate - determining ) 2 ) CO + NaOH → NaHCO ( bicarbonate formation at high pH ) 3 ) NaHCO + Ca ( OH ) → CaCO + H O + NaOH ( ( NaOH recycled to step 2 ) - hence a catalyst ) This sequence of reactions explains the catalytic role played by sodium hydroxide in the system and why soda lime is faster in chemical reactivity than calcium hydroxide alone. It reacts much more quickly and so contributes to a faster elimination of the CO from the rebreathing circuit. The formation of water and the moisture from the respiration also act as a solvent for the reaction. Reactions in aqueous phase are generally faster than between a dry gas and a dry solid. Analogy with the alkali - silica reaction A quite didactic parallelism can be drawn between the catalytic role of sodium hydroxide in the process of carbonation of soda lime and the role of sodium hydroxide played in the alkali - silica reaction, a slow degration process causing the swelling and the cracking of concrete containing aggregates rich in reactive amorphous silica. In a very similar way, NaOH greatly facilitates the dissolution of the amorphous silica. The produced sodium silicate then reacts with the calcium hydroxide ( portlandite ) present in the hardened cement paste to form calcium silicate hydrate ( abbreviated as C-S-H in the cement chemist notation ). This silicification reaction of Ca ( OH ) on its turn continuously releases again sodium hydroxide in solution, maintaining a high pH, and the cycle continues up to the total disappearance of portlandite or reactive silica in the exposed concrete. Without the catalysis of this reaction by sodium or potassium soluble hydroxides the alkali - silica reaction would not proceed or would be limited to a very slow pozzolanic reaction. The alkali silica reaction can be written like the soda lime reaction, by simply substituting CO by SiO in the reactions mentioned here above as follows : reaction 1 : SiO + NaOH → NaHSiO ( silica dissolution by NaOH : high pH ) reaction 2 : NaHSiO + Ca ( OH ) → CaSiO + H O + NaOH ( C-S-H precipitation and regeneration of NaOH ) sum ( 1 + 2 ) : SiO + Ca ( OH ) → CaSiO + H O ( global reaction = Pozzolanic reaction catalysed by NaOH ) See also Carbon dioxide scrubber Alkali - silica reaction ( ASR ) References ^ Jump up to : J. Jeff Andrews ( 1 September 2005 ). `` Anesthesia Systems ''. In Paul G. Barash ; Bruce F. Cullen ; Robert K. Stoelting. Clinical Anesthesia ( 5th ed. ). United States : Lippincott Williams & Wilkins. p. 1584. ISBN 0 - 7817 - 5745 - 2. Retrieved 1 July 2010. ^ Jump up to : Brubakk, Alf O. ; Tom S. Neuman ( 2003 ). Bennett and Elliott 's physiology and medicine of diving, 5th Rev ed. United States : Saunders Ltd. p. 800. ISBN 0 - 7020 - 2571 - 2. Jump up ^ Richardson, Drew ; Menduno, Michael ; Shreeves, Karl ( eds ). ( 1996 ). `` Proceedings of Rebreather Forum 2.0 ''. Diving Science and Technology Workshop. Diving Science and Technology : 286. Retrieved 2009 - 03 - 18. CS1 maint : Multiple names : authors list ( link ) Jump up ^ Lillo RS, Ruby A, Gummin DD, Porter WR, Caldwell JM ( March 1996 ). `` Chemical safety of U.S. Navy Fleet soda lime ''. Undersea Hyperb Med. 23 ( 1 ) : 43 -- 53. PMID 8653065. Retrieved 2009 - 03 - 18. External links Sofnolime MSDS Example of a commercial soda lime product that is used in diving and medicine Publications on sodalime in diving operations An Introduction to Sofnolime ( Technical Article ) Retrieved from `` https://en.wikipedia.org/w/index.php?title=Soda_lime&oldid=842492414 '' Categories : Bases ( chemistry ) Hydroxides Calcium compounds Sodium compounds Anesthetic equipment Rebreathers Catalysis Hidden categories : All articles with dead external links Articles with dead external links from May 2018 Articles with permanently dead external links CS1 maint : Multiple names : authors list Talk Contents About Wikipedia Deutsch Ελληνικά Español Italiano 日本 語 Português Română Русский 中文 3 more Edit links This page was last edited on 22 May 2018, at 20 : 22. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. 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Question: what is the use of soda lime in anesthesia
Answer: to remove carbon dioxide from breathing gases to prevent CO2 retention and carbon dioxide poisoning