Chlorinated lime

Chlorinated lime (also known as bleaching lime ) is a technical mixture of mostly 35% calcium hypochlorite Ca (OCl) ₂ , 30% calcium chloride (CaCl ₂ ) and 13% calcium hydroxide Ca (OH) ₂ . Occasionally, chlorinated lime is described with the semi- structural formula 3CaCl (OCl) · Ca (OH) ₂ · 5H ₂ O.

Chlorinated lime was first made by Charles Tennant in 1799 .

Manufacturing

Chlorinated lime is formed in the cold by the action of chlorine gas on moist slaked lime ( calcium hydroxide ):

${\displaystyle \mathrm {Ca(OH)_{2}+Cl_{2}\longrightarrow CaCl(OCl)+H_{2}O} }$

The conversion to calcium hypochlorite described by the reaction equation does not take place completely, however, so a mixture is formed which also contains calcium chloride and calcium hydroxide.

properties

Chlorinated lime is a white powder or granulate that smells of hypochlorous acid and chlorine . It is only slightly soluble in water. The density is given as 1.5 g · cm ⁻³ .

In the presence of acids or with carbon dioxide from humid air, chlorine gas develops . An example of this is the reaction of sulfuric acid with chlorinated lime:

${\displaystyle \mathrm {CaCl(OCl)+H_{2}SO_{4}\longrightarrow CaSO_{4}+H_{2}O+Cl_{2}} }$

When standing and with some metal oxides, oxygen is released (especially when exposed to light) .

use

Chlorinated lime after a rail suicide on the tracks of the train station in Mainz-Laubenheim : Chlorinated lime has a disinfectant effect

Chlorinated lime was first used successfully as a disinfectant by the physician Ignaz Semmelweis ; this enabled the mortality of women who have recently given birth to be reduced considerably. However, chlorinated lime not only attacks bacteria and viruses, but also the skin. Therefore, the tolerance is not very good and the willingness to use it regularly is low. Alcohol- based hand disinfectants are more widely accepted today . It is also used as an algaecide (algae control agent ) and for the decontamination of warfare agents (e.g. sarin or mustard gas ).

In industry, chlorinated lime or calcium hypochlorite are used as bleaching agents for cellulose , paper and textiles , but are increasingly being replaced by other chlorine-free bleaching processes for environmental reasons.

toxicology

Commercially available preparations of chlorinated lime are provided with the same safety instructions as the main component calcium hypochlorite . It is classified as oxidizing, corrosive, harmful to health and hazardous to the environment. The lethal dose LD ₅₀ is 850 mg kg ⁻¹ for oral ingestion in rats.

Individual evidence

1. ↑ ^{a b c d} Hedinger: Safety data sheet ( Memento from March 16, 2012 in the Internet Archive ) (PDF; 219 kB)
2. ↑ ^{a b c} Entry on chlorinated lime. In: Römpp Online . Georg Thieme Verlag, accessed on June 7, 2014.
3. ^ E. Schweda: Jander / Blasius: Inorganic Chemistry I - Introduction & Qualitative Analysis. 17th edition. Hirzel, 2012, ISBN 978-3-7776-2134-0 . P. 184
4. ↑ According to the written testimony of Ludwig Scheinbrunn from Vienna, a prisoner of the Buchenwald concentration camp , chlorinated lime was used by Martin Sommer, the "executioner of Buchenwald" , to kill prisoners by "placing a bucket of chlorinated lime in his victim's cell, poured water over it and tightly closed the cell. The escaping gas then caused death by suffocation after hours of torture. " See Hackett, David A., Allied Forces. Supreme Headquarters. Psychological Warfare Division. Intelligence Team .: The Buchenwald Report: Report on the Buchenwald concentration camp near Weimar . CH Beck, Munich 1996, ISBN 3-406-41168-1 .