It has come to my attention that an accident has occurred in Kansas in the USA at a distillery (MGP ingredients) which makes alcoholic liquors according to CBS. Now some of you might be asking what is chlorine, what is sodium hypochlorite and what is happening.
Now some of the reports are rather alarming, for example at Reuters the gas cloud was described as being like mustard gas. Now this is a rather alarming and odd statement. Mustard gas and other strong alkylation agents such as trimethylsilyl diazomethane do not strongly irritate the lungs or other parts of the body at the time of exposure, they tend to cause effects hours after exposure. The idea of mustard gas as a chemical weapon is that it gives no strong warning signs to a person, so that they can absorb a dangerous amount and then later the effects start. Thus by the time anyone notices any symptoms it is too late to take action to prevent damage by ending the exposure.
Here is a diagram of sulfur mustard which is the original mustard gas used in world war one. There are some related mustard gases but this is the original and most common one. Its NATO code is HD.
Chlorine is a substance which will irritate the eyes, lungs, mouth and other organs at the time of exposure. Chlorine is a general tissue wrecker which can cause serious lung injuries which can result in death. But the way that it acts is very different to mustard gas. Mustard gas is an alkylation agent which can crosslink DNA, proteins and other biomolecules. I also hold the view that chlorine gas has far less potential to act as a carcinogen (cancer forming agent) on humans.
Now what is sodium hypochlorite, it is commonly sold as a dilute solution for use in the home for cleaning toilets. It is known as chlorine bleach. The substance is made by the reaction of chlorine gas with cold dilute sodium hydroxide solution according to the following equation.
Cl2 + 2NaOH → NaCl + NaOCl
When chlorine gas is bubbled into water then it reacts in a reversible reaction which is shown below.
Cl2 + H2O → HCl + HOCl
The HCl is a strong acid (hydrochloric acid) and the HOCl is a weak acid (hypochlorous acid). So by using a sodium hydroxide solution the forwards reaction is favoured as the acids lose their protons in deprotonation reactions forming the two salts (sodium chloride and sodium hypochlorite).
Now when the sodium hypochlorite solution was mixed with sulfuric acid then the sodium hypochlorite was converted into the free acid again. This would have formed HOCl which is able to react with the chloride anions present in the bleach to form the chlorine gas which escaped from the plant. There are other things which one should not do with chlorine bleach other than mixing it with acid, maybe another day we can discuss these things.