Sciencemadness Discussion Board

Sodium Hypochlorite Fundamentals

Actinium - 13-10-2014 at 09:35

Had a few Questions.
Did my first Haloform reaction between Aceton I had dried and ~qt of NaClO
Now I know it should be dried, then distilled then placed in either an amber or cobalt bottle and added a stabilizer. in this case Water or alcohol.
My question is does the alcohol need be anhydrous or can say everclear be used since it only contains 5% w/v ? when working with it does new alcohol need to be added everytime the Chloroform is used and distilled so as to prevent Phosgene ?
What are the relative time frames where one should be worried about decompostion to an unsafe product?
My last question is since the end water after the reaction contains small amounts of sodium Hydroxide, and this is a stabilizer for the bleach its self can a small amount of this be used to keep it from degrading or is this advised against?
Thank you, safety is always on my mind as well as proper handling and disposal of all Chems.
-Ac-

gdflp - 13-10-2014 at 09:52

First of all, sodium hypochlorite has lots of water in it's solution, so drying the acetone isn't necessary. After the chloroform is distilled, it is a good idea to add more ethanol, though there should still be some in solution due to the close boiling points of the solvents. Anhydrous ethanol is often used, although this is unnecessary unless you need anhydrous chloroform. Remember that sodium hydroxide will destroy chloroform, so this will not work as a stabilizer. I'm don't think that water will stabilize chloroform, though I could be wrong. Time frame for phosgene production will depend on the temperature it is stored at, light level it is stored at, humidity, etc.

aga - 13-10-2014 at 10:49

I read somewhere that when 'old' or suspect chloroform is to be used, it is wise to distill/dry it again before use.

The ethanol reacts with the phosgene, and a product is HCl, causing higher than expected acidity to be present.

As with all unstable reagents, i guess the best thing is to make-for-use rather than Store for years against the time you *may* need it.

Little_Ghost_again - 13-10-2014 at 11:26

Quote: Originally posted by gdflp  
Remember that sodium hydroxide will destroy chloroform,


Hi could you expand and explain this please. I have been making chloroform with IPA and have been adding Hydroxide to it at the start.
I got strange results but I also got chloroform, I think if I understand what the hydroxide does to the chloroform then you would be answering some pretty big questions I have about some the results I have got.

Also dosnt part of the reaction produce hydroxide? if so can you explain what happens to this or how it fits in?
I know this kind of sounds like I am saying your wrong but far from it. I think it may well hold the key to some stuff I have seen.

Many thanks
LG

aga - 13-10-2014 at 12:15

I followed a process on youtube for Haloform, and forgot about it for 3 days.
https://www.youtube.com/watch?v=XYbnNufX5-c

The Yield was pitiful, probably because i left it too long, and the weather was in the Hot range at the time.

At 4:50 in the video, he says the supernatant liquid is 'Alkaline salt water and a small amount of bleach'
At 12:30 he says that "Chloroform hydrolyses when left in an alkaline environment, making Formate and Chloride"

Doesn't say Which Chloride or Formate, presumably because it is Obvious to those who Know.

He also says that "this effectively neutralises the choloform over time, making it safe for disposal"

Is that correct ?

What does it Actually become in an Alkaline solution of NaCl, NaOH or a mix.

I have no immediate or forseeable use of my choloform, and would prefer to Safely dispose of it rather than keep it.

Little_Ghost_again - 13-10-2014 at 12:19

Mentioning no names but I think some would buy it to dispose of by the smelling method :D.
Personally cant stand the smell.

Amos - 13-10-2014 at 12:27

Given enough time, AQUEOUS sodium hyroxide will react with chloroform to form dichlorocarbene and sodium chloride.

CHCl3 + NaOH → CCl2 + NaCl + H2O

The more water involved, the more chloroform can dissolve in the water and react.

Chloroform(in pure form) can be stored pretty much indefinitely, but it should be periodically vented outside if there is much headspace at the top for gas to accumulate. If a stabilizer has been added, it will be good for weeks or even months, but eventually it needs to be washed with sodium bicarbonate(to remove dissolved HCl), dried over a desiccant, re-distilled, and more stabilizer added. Yes, water does decompose phosgene, but considering water and chloroform don't like to dissolve in each other, water probably isn't an option. A good policy is probably just to re-distill the amount of chloroform you need each time you need to use it; I don't have to make use of mine all that often.

Amos - 13-10-2014 at 12:30

Quote: Originally posted by Little_Ghost_again  
Mentioning no names but I think some would buy it to dispose of by the smelling method :D.
Personally cant stand the smell.


I think he's talking about me, guys. I really like chloroform.

Amos - 13-10-2014 at 12:32

Quote: Originally posted by aga  
I followed a process on youtube for Haloform, and forgot about it for 3 days.
https://www.youtube.com/watch?v=XYbnNufX5-c

The Yield was pitiful, probably because i left it too long, and the weather was in the Hot range at the time.

At 4:50 in the video, he says the supernatant liquid is 'Alkaline salt water and a small amount of bleach'
At 12:30 he says that "Chloroform hydrolyses when left in an alkaline environment, making Formate and Chloride"

Doesn't say Which Chloride or Formate, presumably because it is Obvious to those who Know.

He also says that "this effectively neutralises the choloform over time, making it safe for disposal"

Is that correct ?

What does it Actually become in an Alkaline solution of NaCl, NaOH or a mix.

I have no immediate or forseeable use of my choloform, and would prefer to Safely dispose of it rather than keep it.


If you're disposing of it, the best way is to leave it in a large amount of sodium hydroxide solution for a couple of days. Chloroform is difficult to remove from municipal water supplies and it's a major health risk to the general population, so please don't put it down any drains. Pouring it on some concrete and letting it evaporate might be fine too; just don't hang around for the phosgene to show up.

Metacelsus - 13-10-2014 at 12:39

The reaction of chloroform and sodium hydroxide can be dangerously exothermic, especially if there's any kind of phase transfer catalyst present (even ethanol/methanol will do it).
Quote:
A chloroform-methanol mixture was put into a drum contaminated with sodium hydroxide. A vigorous reaction set in, and the drum exploded. Chloroform normally reacts slowly with sodium hydroxide owing to the insolubility of the latter. The presence of methanol (or other solubilizer) increases the rate of reaction by increasing the degree of contact between chloroform and alkali.


http://webwiser.nlm.nih.gov/

Actinium - 13-10-2014 at 20:42

so would it be a good idea to wash it with D.W. to remove salts and the crap I didnt do right away then distille and add the ethanol?

BTW chloroform smell awesome. just ask the ladies.:D

UnintentionalChaos - 13-10-2014 at 21:06

Quote:
Quote: Originally posted by No Tears Only Dreams Now  
Given enough time, AQUEOUS sodium hyroxide will react with chloroform to form dichlorocarbene and sodium chloride.

CHCl3 + NaOH → CCl2 + NaCl + H2O


Yes, and :CCl2 is an extremely reactive intermediate that inserts into the O-H bond on water, eliminates HCl to formyl chloride, and rapidly consumes another equivalent of water to HCl and formic acid.

The whole reaction is occuring in NaOH-containing liquid, so the final product is a dilute solution of NaCl and Sodium formate.

Reaction balance is as follows:

3NaOCl + CH3C(=O)CH3 --> CHCl3 + NaOAc + 2NaOH

Yield from the prep is about 70%. This means that about 1/3 of the CHCl3 stays dissolved or is lost to immediate hydrolysis. This gives the wastewater a ~6:1 ratio of NaOH to CHCl3. Only 3eq of NaOH are needed to consume an eq of chloroform so the waste from the bleach-bottle approach should, on standing, leave you with a dilute solution of NaOH, sodium acetate, sodium formate, and sodium chloride.
Quote: Originally posted by aga  
I followed a process on youtube for Haloform, and forgot about it for 3 days.
https://www.youtube.com/watch?v=XYbnNufX5-c


That is my video. I have found reaction temp to pretty strongly influence the yield.

With regards to OP,

When the chloroform has been prepared freshly from bleach, the dilute NaOH should have done a pretty good job already washing it. A rinse with distilled water should remove any alkaline contaminants. After distillation, you need to add an alcohol as stabilizer. Water is not a stabilizer. Everclear should be fine given the small amount needed.

Before using the chloroform (depending on application), you may need to redistill it. If it has sat unused for a long time, especially if not kept cold/dark, you will have some degree of chemical degradation to acidic byproducts. You can check this by shaking a sample with distilled water and using some pH paper. Acidic indicates degradation since in the presence of an alcohol, you form HCl.

To re-purify the material, wash with dilute sodium bicarbonate solution, followed by distilled water. This removes the acidic byproducts and the stabilizer alcohol. Dry over CaCl2, MgSO4, CaSO4, etc. and distill.

Use the dried, freshly distilled chloroform for whatever application you have, if you need dry, pure material. If water content can be tolerated, the 2 washings are probably sufficient.

Any remaining chloroform needs to be restabilized for storage.

[Edited on 10-14-14 by UnintentionalChaos]

Little_Ghost_again - 14-10-2014 at 02:35

Quote: Originally posted by Actinium  
so would it be a good idea to wash it with D.W. to remove salts and the crap I didnt do right away then distille and add the ethanol?

BTW chloroform smell awesome. just ask the ladies.:D


Our vicar told me chloroform makes your bum sore.