Sciencemadness Discussion Board

Highest Sodium Hypochlorite Concentration that can be made SAFELY ?

LuckyWinner - 24-11-2020 at 10:09

This Sodium Hypochlorite solution will be used to make chloroform.
A high concentration wants to be used to decrease the volume of the chloroform reaction.


I saw a youtube video
----------------------------
Make concentrated sodium hypochlorite (bleach)
https://youtu.be/rMcmJeckZoI


Chemicals Used in Video
----------------------
10g sodium carbonate 105.988 g/mol, 0.094mol
48ml distilled water 18.02 g/mol , 2.66 mol
14g calcium hypochlorite powder 142.98 g/mol, 0.098mol

this will result in a 14g Sodium Hypochlorite in 48ml of water
according to this calculator.

https://www.webqc.org/balance.php?reaction=Na2CO3+%2B+Ca%28C...

these 14g of Sodium Hypochlorite/48ml of water = 29.2% sodium hypochlorite solution?

is this correct?



1)Whats the highest stable Sodium Hypochlorite solution that will not degrade quickly at ~6C fridge temperature?

2)The proper concentration of Sodium hypochlorite can be defined correctly
by doing this mol calculation or is a hydrogen peroxide determination a la nilered required?
https://youtu.be/j-PrAczOGb0

since excess acetone will form an azeotrope with chloroform.


[Edited on 24-11-2020 by LuckyWinner]

unionised - 24-11-2020 at 10:19

29.2% what?
https://en.wikipedia.org/wiki/Percent_active_chlorine

LuckyWinner - 24-11-2020 at 11:27

Quote: Originally posted by unionised  
29.2% what?
https://en.wikipedia.org/wiki/Percent_active_chlorine


that means the bleach concentration that are given on bottles refer to the active chlorine content inside the bottle not the complete Sodium Hypochlorite molecule?

1 mol Cl weights 35.453 g in Sodium Hypochlorite NaClO x 0.196 mol yield = 6.95g chlorine
dissolved in 48ml of water , 100/48= 2.08 x 6.95g Cl = 14.48% active chlorine in the solution?

aromaticfanatic - 26-11-2020 at 15:05

I know 10% is sold commercially.

30% is the upper limit of storable I think.

I have had a similar question when I thought of making highly concentrated bleach from baking soda and calcium hypochlorite, and then heating to disproportionate the HClO- into ClO3-

Never did do the experiment but I still wonder what the safest concentration is.

Pumukli - 27-11-2020 at 08:42

How you define "safest"?

It is not an explosive, not a toxic gas, it is a corrosive liquid.

I can't think of any concentration made from calcium hypochlorite, water and sodium carbonate that could not be handled relatively safely even in an amateur environment. Splash hazard - yes, wear goggles and protect your skin and clothes, it does emit chlorine gas but (relatively) slowly, I'd preferably work outdoors or in as cold a solution as possible...

Start small, get know the substance, how to handle it, it won't unexpectedly explode or end up in a thermal runaway if you are reasonably careful.

BUT: Resist the temptation of flooding dry calcium hypochlorite powder with oxidizable organic liquids! It can (and most probably will) "explode" under these circumstances! But you want to make a solution at first, yes?

symboom - 27-11-2020 at 09:30

Source
Atomisty.com


Solutions containing a high percentage of sodium hydroxide yield a concentrated solution of the hypochlorite, provided additional alkali is introduced periodically to maintain the concentration of the solution. Under these conditions, the sodium chloride produced by the reaction is precipitated, and a solution of hypochlorite obtained which reacts with hydrochloric acid to yield up to 49.2 grams of chlorine per 100 c.c. of solution. The temperature of the reaction should be maintained below 27° C., but the very concentrated solutions obtained lack stability, the hypochlorite changing to a mixture of chloride and chlorate, one molecule being oxidized at the expense of another. From very concentrated solution sodium hypochlorite separates as a solid hydrate, its composition approximating more nearly to that of the heptahydrate than the hexahydrate. It is a very unstable, hygroscopic substance, but dehydration in a current of dry air at reduced pressure converts it into the solid anhydrous hypochlorite, which melts about 45° C. It is less hygroscopic than the hydrate, and contains 40 to 60 per cent, of available chlorine.

When the turbid liquid formed by heating the heptahydrate at 20° C. is cooled slowly to the ordinary temperature, large greenish-yellow, very deliquescent crystals of the pentahydrate are formed. They melt at 27° C., and are stable at ordinary temperature in absence of air.

Sodium hypochlorite is also manufactured by the electrolysis of sodium-chloride solution without a diaphragm, the solution being less concentrated than that prepared by the chlorine process from sodium hydroxide, but free from the excess of alkali characteristic of that prepared by the older method. The process is carried out either in the apparatus designed by Kellner, or in that of Haas-Oettel, sodium chlorate being a by-product (v. infra). It is noteworthy that electrolysis of sodium-chloride solution with an alternating current also produces sodium hypochlorite.

aromaticfanatic - 27-11-2020 at 10:08

Quote: Originally posted by Pumukli  
How you define "safest"?

It is not an explosive, not a toxic gas, it is a corrosive liquid.

I can't think of any concentration made from calcium hypochlorite, water and sodium carbonate that could not be handled relatively safely even in an amateur environment. Splash hazard - yes, wear goggles and protect your skin and clothes, it does emit chlorine gas but (relatively) slowly, I'd preferably work outdoors or in as cold a solution as possible...

Start small, get know the substance, how to handle it, it won't unexpectedly explode or end up in a thermal runaway if you are reasonably careful.

BUT: Resist the temptation of flooding dry calcium hypochlorite powder with oxidizable organic liquids! It can (and most probably will) "explode" under these circumstances! But you want to make a solution at first, yes?


I was thinking more of a thermal runaway than a proper explosion. I have yet to look up delta H of the disproportionation of ClO- but if I begin to heat a say, 90% solution and it begins to disproportionate very fast it could cause a runaway. Lots of bumping boiling that can break a flask or in very extreme cases explode the flask sending shards. I think that is more often an issue for very volatile liquids like ether but I don't want to be the one to find out.

LuckyWinner - 27-11-2020 at 13:51

can anyone tell me if this is correct?


Chemicals Used in Video on how to make Sodium Hypochlorite solution
----------------------------------------------------------------------------------------
10g sodium carbonate 105.988 g/mol, 0.094mol
48ml distilled water 18.02 g/mol , 2.66 mol
14g calcium hypochlorite powder 142.98 g/mol, 0.098mol

this will result in a 14g Sodium Hypochlorite in 48ml of water
according to this calculator.

https://www.webqc.org/balance.php?reaction=Na2CO3+%2B+Ca%28C...

these 14g of Sodium Hypochlorite/48ml of water = 29.2% sodium hypochlorite solution?


WHY does the video say his solution is at a concentration of 20%? Its 29.2% !?



post 2 in this thread,
said its not 29.2% sodium hypochlorite in solution, what is it then?

I want to use this to make chloroform but I guess 29.2% is too high.
20% sodium hypochlorite by weight in water is good and stable at 15C ?



https://en.wikipedia.org/wiki/Sodium_hypochlorite
..Household bleach is, in general, a solution containing 3–8% sodium hypochlorite, by weight

[Edited on 27-11-2020 by LuckyWinner]