Soda lime

Soda lime removes the CO ₂ content of the air in this absorption filter for measuring devices .

Drägersorb® Soda Lime

Soda lime is used in anesthesia machines and in closed circuit diving machines (rebreather or diving rescuer ) to bind carbon dioxide contained in the exhaled air in order to prevent the harmful effects of an excessively high carbon dioxide content in the inhaled air . Soda lime is also used in space travel .

In medicine and diving, a mixture of calcium hydroxide Ca (OH) ₂ and sodium hydroxide NaOH is used, previously also potassium hydroxide KOH and barium hydroxide Ba (OH) ₂ . Soda lime to chemically bind carbon dioxide was introduced by Ralf Waters in 1924 .

The following chemical reactions take place between soda lime and carbon dioxide:

1: ${\displaystyle \mathrm {CO_{2}+\ H_{2}O\rightleftharpoons H_{2}CO_{3}} }$

2: ${\displaystyle \mathrm {H_{2}CO_{3}+2\ NaOH\rightleftharpoons Na_{2}CO_{3}+2\ H_{2}O} }$

3: ${\displaystyle \mathrm {Na_{2}CO_{3}+\ Ca(OH)_{2}\rightleftharpoons CaCO_{3}+2\ NaOH} }$

100 g sodium hydroxide can bind up to 23 liters of carbon dioxide. Average absorbers can absorb 10-15 liters per 100 g. The optimal granulate cross-section is 2.5 mm. A pH indicator is added to the soda lime , which changes its color from white to purple when the pH value is low, indicating that the absorber has been used up.

Use in medicine

Soda lime is used in anesthesia when rebreathing techniques are used to remove carbon dioxide from the air we breathe. A container filled with soda lime, the absorber, is an essential component of all anesthetic rebreathing systems. After completing an operation, the absorber must be replaced.

Disposal of soda lime

Due to the proportion of sodium hydroxide and unreacted calcium hydroxide, used soda lime is considered to be waste that requires special monitoring and must be disposed of under the waste key number 180106 *. Furthermore, soda lime must be disposed of with a collection / disposal certificate in order to ensure that this material is properly disposed of.

literature

• Ralph M. Waters: Clinical scope and utility of carbon dioxide filtration anesthesia. In: Anesthesia & Analgesia , Vol. 3 (1924), pp. 20-22, ISSN  0003-2999 .

Individual evidence

1. ↑ Waste manager medicine: disposal of anesthetics. Retrieved January 7, 2020 . 
2. ↑ Federal / State Working Group on Waste (LAGA): Valid notifications from LAGA (as of July 2019). Retrieved January 7, 2020 . 
3. ↑ Waste manager medicine: verification of the disposal of waste. Retrieved January 7, 2020 .