nimgoldman
Hazard to Others
Posts: 303
Registered: 11-6-2018
Member Is Offline
|
|
Chloroform reaction mixture disposal (acetone + bleach method)
I have recently synthesized chloroform using 6 500 mL of 7% sodium hypochlorite mixed with 95% molar deficit in acetone.
The leftover waste mixture contains some sodium hypochlorite and maybe a considerable amount of chloroform (given its solubility in water, it should
be something like 50 grams or 30 mL).
I know that the hypochlorite can be destroyed with either sodium metabisulfite or hydrogen peroxide.
Unfortunately, the destruction methods for chloroform are more difficult except for adding sodium hydroxide and letting it react for a long time to
form dichlorocarbene.
Another option is simply boiling it off, but this is impractical for such a large amount of water.
So I am thinking about simply adding sodium metabisulfite and some sodium hydroxide (AFAIK the two don't react together), then let the canister stand
for two months or so before pouring it down the drain with additional fresh water.
Is this the correct disposal technique or would you advice otherwise?
|
|
|
Ubya
International Hazard
Posts: 1232
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline
Mood: I'm a maddo scientisto!!!
|
|
sodium hypochlorite (bleach) is commonly used in sanitation, it's not a problem to just drain it in the sink, it will just oxidize something in the
sewers.
chloroform on the other hand is a halogenated solvent, really harmful for water and atmosphere chemistry, it must be disposed correctly, the only way
i know is as you said to add sodium hydroxide, wait a long time so that dichlorocarbene is formed transformed in formate and NaCl
---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
|
|
|
woelen
Super Administrator
Posts: 7976
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
I would pour all the liquid in a big dish and allow it to evaporate slowly. Let it stand for a few days. Even if not all water has evaporated, the
chloroform will be long gone after a few days. Just put the dish outside at a place where children and animals (beware of birds who want to drink
something) cannot access it.
Chloroform should not get in the ground water or in the sewers. It only very slowly decomposes in water under dark conditions. In air, exposed to
daylight, on the other hand, it fairly quickly is decomposed, the final products being CO2 and chloride ions. Its atmospheric half life is 3 to 5
months. I read that chloroform is a natural constituent of earth's atmosphere, at very low concentrations, produced by seaweed. Your 30 ml will be
swamped by the natural background amount and after a few months it will be gone anyway.
|
|
|
Herr Haber
International Hazard
Posts: 1236
Registered: 29-1-2016
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Ubya
the only way i know is as you said to add sodium hydroxide, wait a long time so that dichlorocarbene is formed transformed in formate and NaCl
There should be more than enough NaOH in the bleach dont you think ?
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
|
|
|
nimgoldman
Hazard to Others
Posts: 303
Registered: 11-6-2018
Member Is Offline
|
|
I have not used household bleach but a commercial sodium hypochlorite solution. It was originally 12% but it over year old and the actual
concentration lowered to 7% (determined by titration).
Unfortunately I live in an appartment and cannot put the waste water on terrace because of the birds...
I will thus add sodium hydroxide and wait.
|
|
|
Ubya
International Hazard
Posts: 1232
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline
Mood: I'm a maddo scientisto!!!
|
|
Quote: Originally posted by Herr Haber
||
|| Quote: Originally posted by Ubya
|| the only way i know is as you said to add sodium hydroxide, wait a long time so that dichlorocarbene is formed transformed in formate and NaCl
||
|| There should be more than enough NaOH in the bleach dont you think ?
||
quote from wikipedia: Household bleach is, in general, a solution containing 3–8% sodium hypochlorite, by weight, and 0.01–0.05% sodium hydroxide;
the sodium hydroxide is used to slow the decomposition of sodium hypochlorite into sodium chloride and sodium chlorate.[34]
0.01-0.05% i don't think is enough
---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
|
|
|
nimgoldman
Hazard to Others
Posts: 303
Registered: 11-6-2018
Member Is Offline
|
|
Suprisingly, the light-green waste solution turned brown/red over last few days. It smells of acetone even though I've added 5-7% molar deficit of
acetone relative to hypochlorite.
I hope I have not screwed up the titration. But judging by the colour after reaction, there was still some hypochlorite left, meaning the acetone
should have been consumed in the reaction. On the other hand, the haloform reaction might have proceeded over the days...
Anyway, sodium hydroxide have been added and the canister sits in the lab. I will move it outside later.
[Edited on 3-8-2019 by nimgoldman]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
