Sciencemadness Discussion Board

Chlorite and hypochlorite interactions

woelen - 22-5-2011 at 04:52

Inspired by some posts of AJKOER in the thread on NaClO2 disposal I decided to do some experiments with this.

It can be stated that hypochlorite and chlorite do not interact appreciably when in alkaline solutions or near neutral solutions, but when acid is added, then quite some interesting things occur.


I prepared a solution of around 30% NaClO2 and used this for all further experiments.

When a 30% NaClO2 solution is poured on solid Ca(ClO)2, then no reaction occurs. The Ca(ClO)2 does not dissolve, much less so than in plain water.
When some acid is added to this mix, then a very vigorous reaction starts, much more so than with NaClO2 alone or Ca(ClO)2 alone. A big plume of ClO2 was ejected from the mix. The vigor of the reaction was comparable with that of adding 10% HCl to baking soda, in which a very fast evolution of CO2 occurs. In this experiment I had the same, but now ClO2 is evolved instead of CO2. No chlorine is formed, at least no smell of chlorine could be perceived, while there was a strong spicey smell of ClO2.
Actually, this reaction scared me somewhat, because I had a really big cloud of ClO2. Inside the solid/liquid mix there were occasional strong crackling noises, probably due to explosions of small pockets of ClO2. The chlorine, formed in these explosions, however, did not make it into the air, this chlorine reacts with surrounding NaClO2.


Next, I decided to do some better controlled experiments:

1) Take 1 ml of NaClO2-solution and dilute with 5 ml of water.
2) Take 1 ml of NaClO2-solution and dilute with 5 ml of 4% bleach.
3) Take 5 ml of 4% bleach.
Add half a ml of 30% HCl to all three liquids and swirl somewhat. The result is as follows:
1) Liquid becomes deep yellow and some ClO2 is released to the air above the liquid. When carefully sniffed, the smell of ClO2 can be perceived, but the smell is not choking. There is no Cl2.
2) Result is very similar to (1), but more ClO2 is formed. The air above the liquid becomes deep yellow. Careful smelling gives the same result as in (1).
3) A lot of gas bubbles are formed and a pale green color can be seen above the liquid. Even without smelling near the open end of the test tube I had to step aside for a few moments due to the strong and choking smell of the chlorine gas.

Reaction (3) is the standard reaction in which Cl2 is formed from hypochlorite and chloride.
In reaction (1), the chlorite and chloride of the hydrochloric acid from ClO2.
In reaction (2), there is a very interesting observation. The hypochlorite does not lead to formation of chlorine, but it contributes to the formation of ClO2. Apparently, hypochlorite acts as oxidizer in this case and oxidizes ClO2(-) to ClO2.

So, there is indeed an interaction between hypochlorite and chlorite, but only at low pH:

ClO2(-) + H(+) --> HClO2
ClO(-) + H(+) --> HClO

2HClO2 + HClO --> 2ClO2 + Cl(-) + H2O + H(+)

No chlorine is formed at all.


Finally, I took a smaller sample of solid Ca(ClO)2 and added some solid NaClO2. I carefully added dilute nitric acid to assure that no chloride is added. When this is done, a vigorous reaction is started and the test tube immediately is filled with a very intensely colored yellow gas.
Ignition of this test tube full of gas gives a loud roaring noise. This means that the gas mix must be very pure ClO2(proably near 100%). The explosion was very powerful for such a small volume of gas and came close to the power of an explosion of detonating gas of similar volume.

Rogeryermaw - 22-5-2011 at 10:01

excellent work as usual woelen. your descriptions are clear and detailed. a true scientist! it is also a dismal fact that, being from the netherlands, your command of the english language is easier to follow than most english speaking americans...

thank you for the hard work and for sharing your results!

AJKOER - 22-5-2011 at 10:07

Great experiments!

Method 1 of adding HCl to NaClO2 should produce more ClO2, but requires an excess of NaClO2. Reaction is:

5 NaClO2 + 4 HCl → 5 NaCl + 4 ClO2 + 2 H2O

So called Hypochlorite method for preparation of ClO2 is:

2 NaClO2 + 2 HCl + NaOCl → 2 ClO2 + 3 NaCl + H2O

apparently works well.

I believe your reaction of HOCl and HClO2 is actually reversible, forming HClO3 and HCl as I have seen this reverse reaction (not identified as reversible) in wikipedia article on ClO2:

HClO3 + HCl <===> HClO2 + HOCl

HClO3 + HClO2 → 2 ClO2 + Cl2 + 2 H2O

Now, when you used dilute HNO3 and added it to Ca(ClO)2 and NaClO2:

Ca(ClO)2 + 2 HNO3 --> Ca(NO3)2 + 2 HClO
NaClO2 + HNO3 --> NaNO3 + HClO2

So by the reactions above, HClO2 + HClO3 (where the HClO3 is from HClO + HClO2) produce a mixture of ClO2 and Cl2. However, your observations interestingly suggest something different. There was at one time a debate over the existence of the chlorous anhydride, Cl2O3, latter shown to be a mixture of ClO2 and Cl2. Now, the decomposition of Cl2O3 should be more explosive than ClO2, which was perhaps your observation?


.

Formatik - 22-5-2011 at 10:14

Quote: Originally posted by woelen  
It can be stated that hypochlorite and chlorite do not interact appreciably when in alkaline solutions or near neutral solutions, but when acid is added, then quite some interesting things occur.


When alkaline they do interact, however. As mentioned in Gmelin, in 0.05 to 1.2 n-alkaline solution, NaClO and NaClO2 at 25 to 50 deg. react according to the equation:

NaClO + NaClO2 = NaClO3 + NaCl

The speed of the reaction corresponds to the equation: dx/dt = K (a-x) (b-x), where a and b are the starting quantities of NaClO and NaClO2. The value of K increases with increasing NaOH content.

Also described in literature is if a hypochlorite-containing chlorite solution has CO2 led into it, it quickly turns yellow due to ClO2 formation according to the equation: HClO + HClO2 = ClO2 + Cl + H2O (Bray, Z. anorg. Ch. 48 [1906] 233).

AndersHoveland - 22-5-2011 at 11:45

These equations may be helpful:

(8)HOCl --> (4)H2O + (2)ClO2 + (3)Cl2

(8)HClO2 --> (4)H2O + (6)ClO2 + Cl2

The important question is whether chlorine oxidizing chlorite is more favorable than hypochlorous acid oxidizing chlorite; to be more specific, which of the following three reactions predominates?

(A) Cl2 + ClO2[-] --> Cl(-) + ClO2

(B) (2)OCl[-] + ClO2[-] + (2)H[+] --> ClO3[-] + H2O + Cl2

(C) Cl[-] + OCl[-] + (2)H[+] --> H2O + Cl2

If reaction (A) is predominates, then one of the possible net equations could be:

(8)OCl[-] + (6)ClO2[-] + (8)H[+] --> (6)Cl[-] + (4)H2O + (8)ClO2

If either reactions (B) or (C) predominate over reaction (A), then chlorine gas will also be generated. It would be difficult to know by examing the gaseous products from the reaction, as making a distinction between ClO2, and a mixture of both ClO2 and Cl2, can be very difficult.

The exact ratio of reaction products probably depends on the pH. Mild acidity will likely give a gas that is mainly ClO2 (and a 1 to 2 ratio of chlorine to oxygen from the partial decomposition of this unstable gas), whereas the escaping gas from the reaction done using a more acidic solution is likely to have a higher ratio of chlorine in it.

Just my opinion.

I do not know if reaction (B),
(2)OCl[-] + ClO2[-] + (2)H[+] --> ClO3[-] + H2O + Cl2 *
could actually happen. The "Hypochlorite method" for making chlorine dioxide involves chloride ions (both from the HCl and contaminants in the NaOCl bleach),
(2) NaClO2 + (2) HCl + NaOCl --> (2) ClO2 + (3) NaCl + H2O
It would be interesting to know if reaction (B) would happen instead if the initial reactants did not contain any chloride ions, by using pure sodium chlorite, nitric acid, and calcium hypochlorite, as Woelen has done. (while most sources of calcium hypochlorite also contain 30% chloride contaminants, the proportion of hypochlorite to chlorine would still be great enough so that the main reaction could potentially be equation (B), with the direct evolution of chlorine, and production of chlorate)

Certainly with excess acid (with none of the reactants containing chloride), a mixture of hypochlorite and chlorite would yield only chlorine dioxide and chlorine (no chlorate).
(2)HOCl + (2)HClO2 --> (2)H2O + (2)ClO2 + Cl2

*chlorate could also potentially be produced, even if reaction (A) predominates over (B), so long as reaction (B) predominates over reaction (C), the equation then being:
(2)OCl[-] + (3)ClO2[-] + (2)H[+] --> ClO3[-] + (2)Cl[-] + H2O +(2)ClO2

Woelen, as usual, you have presented us with a perplexing question!

[Edited on 22-5-2011 by AndersHoveland]

woelen - 23-5-2011 at 06:45

I could try the validity of some of your equations.

Equation (A) can easily be tested by bubbling chlorine through a neutral solution of NaClO2.

I have doubts about equation (B). Why formation of chlorate and at the same time Cl2? Why not chlorate and chloride?

Equation (C) definitely occurs, it is a well-known method of making chlorine gas from hypochlorite.
Quote:
making a distinction between ClO2, and a mixture of both ClO2 and Cl2, can be very difficult.
This is not that difficult. If only ClO2 is formed in a reaction, then the smell of the gas is quite mild. By CAREFULLY sniffing the gas or mix of gases you definitely notice the difference between a mix which contains Cl2 and a mix which only contains ClO2 and no Cl2. If even a tiny fraction of the gas mix is Cl2, then you will notice VERY strong irritation of the nose and higher respitory tract, while this is not the case when only ClO2 is present.

ClO2 is less toxic than Cl2, but also somewhat more insidious. ClO2 does not really irritate when breathed, but in high concentrations it certainly can do harm. So, also with ClO2 one must be careful and one must assure not to breathe too much of the gas. Exposure to a concentration of 150 to 200 ppm for one hour may lead to lethal delayed effects, so be careful. Chlorine on the other hand, does not allow exposure to 150 ppm concentration at all. If you breathe air with that concentration of chlorine then it feels as if someone blows you down with a hammer and your lungs are on fire in mere seconds!

AJKOER - 23-5-2011 at 07:17

To strenghten with a different reference the fact the hypochlorite disportionation occurs in both acidic and basic environments, please see the reference: "Handbook of Detergents: Production Volume 142", pages 444 to 445 by Uri Zoller and Paul Sosis. Actual Ph ranges are detailed.

This is a Google book and these pages can be viewed online:

http://books.google.com/books?id=dXn3aB1DKk4C&pg=PA247&a...

My personal observation is that in high Ph situations, to speed up the reaction the solution has to be heated for at least an hour.

woelen - 23-5-2011 at 09:34

@AJKOER: I am not saying that hypochlorite does not disproportionate in alkaline solution. The only thing I question is the mechanism of this disproportionation.

The disproportionation of hypochlorite is used extensively in chlorate cells to make chlorates by means of electrolysis of NaCl or KCl solutions. I also have done that in order to obtain KClO3. In such a cell the conditions usually are somewhat alkaline, especially in cells, set up by amateurs, who do not have sophisticated pH control of the cell.

-------------------------------------------------------------------------------

I also tried what happens if Cl2 is brought in contact with a solution of NaClO2. For this experiment I made Cl2 from calcium hypochlorite and HCl. I bubbled this Cl2 into a long and wide test tube under clean water. I stoppered this test tube in order to have any HCl and remains of the hypochlorite dissolve in the water and then I bubbled the chlorine into another clean test tube, such that this is full with Cl2. The initial amount of Cl2 I had to make was much larger than what I ended up with in the final test tube. I think that almost half of all my chlorine dissolved in the water in the two rinse/bubble sessions.

In a separate test tube I prepared a small quantity of a concentrated solution of NaClO2 (I used the 80% NaClO2 / 20% NaCl stuff from eBay) and then I poured this solution into the test tube filled with Cl2 gas. Immediately, all Cl2 is replaced by ClO2. The color quickly intensifies and also some gas is driven out of the test tube. The ClO2 can be easily ignited, giving a nice roaring noise while it explodes. The reaction must be

Cl2 + 2ClO2(-) --> 2Cl(-) + 2ClO2

I'm quite sure that the liquid contained excess NaClO2 and then the above reaction almost certainly is the one which occurs. The absorption of chlorine is so complete that no Cl2 can even be smelled near the test tube. It really is sucked up by the solution of NaClO2 and I find this quite surprising.

I repeated the experiment another time and now I poured an excess amount of a solution of NaNO2 into the test tube. The liquid noticeably heats up in that case, all ClO2 almost immediately disappears and instead a faint brown color of NO2 can be observed. The presence of NO2 means that the liquid must have become acidic by the addition of the nitrite (nitrite decomposes, giving NO and NO2 when acidified). The reaction must have been as follows:

2ClO2 + 5NO2(-) + H2O --> 2Cl(-) + 5NO3(-) + 2H(+)

The H(+) in turn reacts with NO2(-):

2H(+) + 2NO2(-) --> H2O + N2O3 <--> H2O + NO + NO2


All these experiments nicely confirm the reaction between Cl2 and ClO2(-). This is a very efficient and powerful method of making pure ClO2. It also may explain the reaction between hypochlorite, chlorite and acid. In that reaction probably first the hypochlorite reacts with hydrochloric acid to make Cl2 and then this Cl2 reacts with hypochlorite.




[Edited on 23-5-11 by woelen]

AndersHoveland - 23-5-2011 at 10:14

Woelen, after more thought, I think the reactions that may best describe your original experiment, depending on the initial reactant ratios, are:

(3)ClO2[-] + (2)OCl[-] + (2)H[+] --> ClO3[-] + (2)Cl[-] + H2O + (2)ClO2

or
(2)ClO2[-] + OCl[-] + (2)H[+] --> Cl[-] + H2O + (2)ClO2

There will be different reactions depending on the ammount of acid present. If there is excess acid, then the formation of chlorate and chloride will be less favorable. One way to think of this is that the chlorate and chloride products in the above reaction would react away:

ClO3[-] + Cl[-] + (2)H[+] --> H2O + ClO2 + (½)Cl2

Let us now examine the acidification of hypochlorite ions (with no chloride present). While it was originally mentioned that in excess acid the equation is:

(8)HOCl --> (4)H2O + (2)ClO2 + (3)Cl2

If, however, only a limited ammount of acid was present to react, the reaction would be different, with the formation of chlorate:

(3)OCl[-] + (2)H[+] --> ClO3[-] + H2O + Cl2

In a similar way, we can examine the interaction of hypochlorite and chlorite reacting together with, again, only a limited ammount of acid present. Even with chloride ions present, the reaction would be:

(2)ClO2[-] + OCl[-] + (2)H[+] --> Cl[-] + H2O + (2)ClO2

But with additional acid, the reaction would have instead have been:

ClO2[-] + (3)Cl[-] + (4)H[+] --> (2)H2O + (2)Cl2

Alternatively, if the ratio of hypochlorite to chlorite was high enough, no chloride would result in the reaction products, as it would be oxidized to chlorine. But if the proportion of chlorite is sufficiently higher than that of hypochlorite, chloride ions are favored, as any chlorine would react with the excess chlorite.

The reaction Cl2 + (2)ClO2[-] --> (2)Cl(-) + (2)ClO2, which you have already verified, is well known. It is somewhat unusual that chlorine dioxide (0.96 V) is a weaker oxidizer than chlorine (1.36 V), in terms of reduction potentials.

Again, many different reactions are possible, depending on the ratios of reactants.

---------------------------------------------------------------------------

On the subject of the reaction of chlorine dioxide with an excess solution of sodium nitrite, I would think the reaction would be

ClO2 + (4)NaNO2 --> (3)NaNO3 + NaCl + NO

The reaction of chlorine with a solution of excess sodium nitrite is similar, so this test cannot be used to differentiate between Cl2 and ClO2:

Cl2 + (4)NaNO2 --> (2)NaNO3 + (2)NaCl + (2)NO

Note that the reaction will be different if the ratio of chlorine to sodium nitrite is higher, in which case nitrogen dioxide or hydrochloric acid will be produced.

[Edited on 23-5-2011 by AndersHoveland]

woelen - 23-5-2011 at 11:48

I'm quite sure that the reaction with formation of NO does not occur. NO is almost insoluble in water and then I would see bubbles of gas escaping from the liquid (the solutions were quite concentrated). Instead, the color of ClO2 simply disappears and no bubbles are observed. Only when the liquid is shaken, a faint brown color of NO2 can be observed.

kmno4 - 23-5-2011 at 13:05

PDF titled The chemistry of chlorine dioxide by Gilbert Gordon is uploaded in Refereces. I think it can be helpful in discussion.

AndersHoveland - 23-5-2011 at 13:53

Quote: Originally posted by woelen  
I'm quite sure that the reaction with formation of NO does not occur. NO is almost insoluble in water and then I would see bubbles of gas escaping from the liquid (the solutions were quite concentrated). Instead, the color of ClO2 simply disappears and no bubbles are observed. Only when the liquid is shaken, a faint brown color of NO2 can be observed.


When I wrote, "the reaction will be different if the ratio of chlorine to sodium nitrite is higher, in which case nitrogen dioxide or hydrochloric acid will be produced", I meant this to apply to the reaction involving chlorine dioxide also. Obviously, the conditions in the reaction you did where different, you did not add plain aqueous ClO2 to an excess of NaNO2 solution.

Nitrogen dioxide oxidizes sodium nitrite:
NO2(-) + NO2 --> NO3(-) + NO
so if there is excess nitrite and the solution is not acidified with any other reactant, there should not be any nitrogen dioxide directly evolved. If, however, there is some additional acid added (ex. hydrochloric), then there will in fact be NO2 produced. One way of viewing this is that the nitrate ion can oxidize nitric oxide when made acidic (even if only dilute acid) :

(2)NO3[-] + NO + (2)H[+] --> H2O + (3)NO2

The above reaction should not be surprising, as the following equilibriums are well known:
(2)NO2 + H2O <==> HNO2 + NO3[-] + H[+]aq
NO2 + NO + H2O <==> (2)HNO2

I have taken a look at "The chemistry of chlorine dioxide" by Gilbert Gordon. http://books.google.com/books?id=ozcVYIjru2AC&pg=PA157&a...
(see page 159)

I believe many of his equations are technically inaccurate, and need to be taken in the context of pH. These types of reactions are very much pH dependant; a change in acidity can shift the equilibrium towards different products.

The reaction that I wrote in the previous post,
(2)ClO2[-] + OCl[-] + (2)H[+] --> Cl[-] + H2O + (2)ClO2
is substantiated, although he wrote it in the form:
(2)ClO2[-] + HOCl --> (2)ClO2 + Cl[-] + OH[-]

I have disagreement with him in the reaction which he stated as:
(2)HClO2 + HOCl --> HCl + H2O + ClO2
Although this reaction does in fact have some equilibrium, the reaction will only proceed at a higher pH. One of the HClO2 should have been written as the ion ClO2[-], with the HCl similarly being written as Cl[-]. The reason for the disagreement is that ClO2 can actually oxidize HCl.

[Edited on 23-5-2011 by AndersHoveland]

AndersHoveland - 25-10-2011 at 17:54

Silver nitrate can react with sodium hypochlorite to form silver chloride and silver I,III oxide, Ag2O2, is formed, both of which are precipitated. An unknown substance, with bleaching properties, is left behind in the solution. This substance is unstable, and quickly decomposes after several minutes, leaving behind silver chlorate in the solution, which does not bleach. If sodium hydroxide is added to the bleaching substance, oxygen gas is evolved.

A comprehensive treatise on inorganic and theoretical chemistry, Volume 2 By Joseph William Mellor. p271


Although it is really rather speculative on my part, I think the reaction might look something like:

(6)AgNO3 + (6)NaOCl --> (6)NaNO3 + (4)AgCl + Ag2O2 + (2)ClO2


AndersHoveland - 12-12-2011 at 12:13

Perhaps HOCl could be prepared by mixing solutions of Cl2 and ClO2 ?

ClO2 + H2O <==> HClO2 + HClO3

Cl2 + H2O <==> HCl + HOCl

(5)HCl + HClO3 --> (3)H2O + (3)Cl2
(3)HCl + HClO2 --> (2)H2O + (2)Cl2

Or perhaps adding a limited quantity of hydrochloric acid and some other acid (such as sulfuric) to sodium chlorite ? It would be important to keep the solutions very dilute at all times, to keep the gasses dissolved and not to immediately escape.

ClO2[-] + H[+] --> HClO2

HClO2 + HCl --> (2)HOCl ?

AJKOER - 12-12-2011 at 21:18

If you have dilute Chlorine water, just add NaClO (6% solution):

NaClO + Cl2 + H2O --> NaCl + 2 HClO

I'll see if I can find the reference. Alternately, add any weak acid, or very dilute mineral acid, to NaClO.

For more purity, but more difficult, focus on generating Cl2O and dissolve in water. One way is to pass Cl2 over heated moist Na2CO3 (or CaCO3 fresh precipitate):

2 Cl2 + Na2CO3 --> CO2 (g) + 2 NaCl + Cl2O (g)

This is actually a commercial process. Alternately, if Cl2 is directed into a solution of suspended CaCO3 (fresh precipitate), then HClO is formed:

2 Cl2 + CaCO3 + H2O --> CaCl2 + CO2 (g) + 2 HClO

A process I would not recommended, even though the formation of Cl2O is cited in Wikipedia, is by passing CO2 over moist Bleaching powder. While Cl2O may indeed be initially created, I read that some authors suspect that the Cl2O may further react with CaCl2 reducing the Cl2O back to Cl2. Note the reaction of H2CO3 on pure Ca(OCl)2:

Ca(OCl2) + H2CO3 --> CaCO3 (s) + 2 HClO

and using CO2 on moist Ca(OCl)2 basically dehydrates the HClO to Cl2O, but this may be only half the reaction in the presence of CaCl2.

[Edited on 13-12-2011 by AJKOER]

[Edited on 13-12-2011 by AJKOER]

AndersHoveland - 12-12-2011 at 21:58

Quote: Originally posted by AJKOER  
Alternately, add any weak acid, or very dilute mineral acid, to NaClO.


Unfortunately, this does not work because chloride ions are almost always present in sodium hypochlorite solutions.
Cl[-] + OCl[-] + (2)H[+] --> H2O + Cl2

I am not aware of any chemical company that sells pure NaOCl water solution.

It could, however, be done with calcium hypochlorite. It is possible, under proper conditions to precipitate Ca(OCl)2 from a solution of CaCl2.

AndersHoveland - 14-12-2011 at 17:09

I would wonder if there is any convenient way to prepare sodium hypochlorite solutions mostly free from the presence of chloride ions ? I suspect that such a regent would behave very differently in chemical reactions than the commonly available hypochlorite bleach that contains an equal proportion of chloride. The problem is that, when acidified, HCl inevitibly forms in such solutions, which acts as a reducing agent towards the various chlorine oxides.

Quote:

A solution of free hypochlorous acid is obtained by shaking chlorine water with yellow mercuric oxide until the solution no longer smells of chlorine:
2 HgO + 2 Cl2 + H2O = (HgCl)2O + 2 HOCl
Brown, insoluble mercuric basic chloride is formed from the reaction, and the solution contains hypochlorous acid. If the solution is poured off from the basic mercuric salt and distilled, a pure solution of hypochlorous acid will be obtained; which however, cannot be kept long in the light, for it decomposes into hydrochloric acid and oxygen:
2 HOCl --> 2 HCl + O2

Analytical chemistry, Volume 1, Frederick Pearson Treadwell, William Thomas Hall, p314

It should also be mentioned that, despite the tendancy of hypochlorous acid to decompose into HCl and O2, oxygen actually has a stronger affinity for the hydrogen than chlorine.
Quote:

A gaseous mixture of hydrogen chloride and oxygen, in proportion of 4 volumes of HCl and 1 volume of O, was enclosed in a tube, and submitted to the action of the electric spark for some hours; nine-tenths of the mixture was decomposed, with the formation of free chlorine and water.

Inversely, a weighed quantity of water, enclosed with free chlorine, was decomposed in a similar arrangement to the extent of one-tenth of the oxygen being being liberated.

The former reaction takes place easily, when the mixed gases are passed through a red-hot porelain tube, and the latter reaction, as is well known, occurs by itself at the ordinary temperature, especially in the presence of sunlight.

"Reciprocal Displacements between Oxygen, Sulfur, and the Halogens, when combined with Hydrogen." by Berthelot
Scientific American: Supplement, Volume 7, No. 175, p297


Red hot copper sulfate can also be used as a catalyst to "burn" hydrogen chloride gas in air. I also suspect that nitric oxide could catalyse the room-temperature oxidation of anhydrous hydrogen chloride by oxygen, since HCl is oxidized by NO2 with the formation of nitrosyl chloride, NOCl.
(for information potentially relating to this possibility , see the threads in this forum "help make white fuming nitric acid"-pages 2 and 3, and the thread "HCl + NaNO3" )

[Edited on 15-12-2011 by AndersHoveland]

woelen - 15-12-2011 at 23:34

Pure hypochlorite without appreciable amounts of chloride is available commercially and even OTC. Calcium hypochlorite for swimming pools is fairly pure Ca(OCl02.2H2O. It contains some Ca(OH)2 and CaCO3 as well and only small amounts of CaCl2. When this is added to dilute HNO3, then a clear solution is obtained and hardly any Cl2 escapes from this liquid. When it is added to HCl of similar concentration, then a lot of Cl2 bubbles out of the solution.

AndersHoveland - 16-12-2011 at 00:00

Could almost pure NaOCl solution be prepared by reacting sodium sulfate with calcium hypochlorite, the insoluble calcium sulfate precipitating out?

AndersHoveland - 29-12-2011 at 14:57

This below post is all theoretical. I was thinking about the reactions of these types of chlorine compounds, comparing different possible reactions, (the thought had intially occurred to me that reacting a large excess chlorine with chlorite might change the reaction, so I wanted to see if that was likely, which I finally came to the opinion that it is not).

First, the literature clearly states that chlorine reacts with chlorite to form chloride and chlorine dioxide, and this is supported by the published reduction potentials.

(A) 2 NaClO2 + Cl2 --> 2 NaCl + 2 ClO2

There are two additional reactions which seem to me must be true, although I cannot find them anywhere in the literature.

(B) 8 HOCl <==> 2 ClO2 + 3 Cl2 + 4 H2O

(C) NaCl + 6 HOCl --> NaClO3 + 3 H2O + 3 Cl2

Assuming that all three reactions (A,B, and C) are true, I tried to combine them to form a new reaction.

Here is my work. You do not have to look at it, which is why I am putting it into a 'quotation box' , but I am including it here for anyone that wants to take the trouble,
Quote:

First, I multiplied both sides of reaction B by a multiple of 3, and reaction C by a multiple of 4, to result in the least common denominator to subsequently be able to substitute the quantity of HOCl from one reaction to the other. Reaction A was also multiplied by a multiple of 3.

4 NaCl + 24 HOCl --> 4 NaClO3 + 12 H2O + 12 Cl2

24 HOCl <==> 6 ClO2 + 9 Cl2 + 12 H2O

6 NaClO2 + 3 Cl2 --> 6 NaCl + 6 ClO2

Now combining all three reactions,
6 NaClO2 + 12 Cl2 + 12 H2O --> 2 NaCl + 4 NaClO3 + 12 H2O + 12 Cl2
and simplifying,
3 NaClO2 --> NaCl + 2 NaClO3
I will name this last reaction (D).


(D) 3 NaClO2 --> NaCl + 2 NaClO3

If reactions B and C are both true, it would imply that reaction D is also true. Reaction D is known to occur, but only when it is heated to disproportionate. It may also likely disproportionate under acidic conditions, such as if some dilute H2SO4 was added, although I do not know for certain.

Logically, from the association I have just made, either reaction B or reaction C could only happen when the solution is being heated, or possibly when acidified, although the reactants may be sufficient to acidify the solution themselves.

The above are only thoughts, that hopefully will bring some insight.

I would think that reaction B must be true, that hypochlorous acid must be interchangeable with an aqueous solution containing both chorine and chlorine dioxide.
8 HOCl <==> 2 ClO2 + 3 Cl2 + 4 H2O

The below reactions are known to be true:
2 ClO2 + H2O <==> HClO2 + HClO3
Cl2 + H2O <==> HCl + HOCl
3 HCl + HClO2 --> 2 Cl2 + 2 H2O
8 HCl + 2 ClO2 --> 5 Cl2 + 4 H2O
Chlorate can also be reduced by hydrochloric acid, but I do not know several important details of this reaction.

So I see no reason that ClO2 and Cl2 in H2O should not have equilibrium with HOCl. Perhaps I am failing to realise something obvious?

For reaction C, I would think it would be true, because:

NaCl + HOCl <==> NaOCl + HCl
HCl + HOCl <==> Cl2 + H2O

I would think that hypochlorous acid could oxidize hypochlorite ions to chlorate, but perhaps I am wrong, perhaps it requires much more acidic conditions?

NaOCl + 4 HOCl --> NaClO3 + 2 Cl2 + 2 H2O ??

[Edited on 29-12-2011 by AndersHoveland]

AJKOER - 30-12-2011 at 12:34

AndersHoveland: On the questioned reaction:

NaOCl + 4 HOCl --> NaClO3 + 2 Cl2 + 2 H2O ??

Please see "Handbook of Detergents: Production Volume 142", pages 444 to 445 by Uri Zoller and Paul Sosis.

NaClO + HOCl --> NaClO2 + HCl (slow limiting step, pH in vicinity of 7 for max yield per my recollection)

NaClO2 + HOCl --> NaClO3 + HCl

And, the created HCl would cause the Chlorine generation you included in the presence of additional NaClO via:

HCl + HOCl <==> Cl2 + H2O

as even dilute HCl or any weak acid or very dilute mineral acid will create the needed HOCl upon reacting with NaClO.

Source: "Handbook of Detergents: Production Volume 142", pages 444 to 445, by Uri Zoller and Paul Sosis.

LINK (note, preview currently limited for this google book, equations per my recollection):

http://books.google.com/books?id=dXn3aB1DKk4C&pg=PA247&a...

AJKOER - 31-12-2011 at 17:59

Quote: Originally posted by AJKOER  


Please see "Handbook of Detergents: Production Volume 142", pages 444 to 445 by Uri Zoller and Paul Sosis.

NaClO + HOCl --> NaClO2 + HCl (slow limiting step, pH in vicinity of 7(REVISED see below) for max yield per my recollection)

NaClO2 + HOCl --> NaClO3 + HCl

Source: "Handbook of Detergents: Production Volume 142", pages 444 to 445, by Uri Zoller and Paul Sosis.



OK, even though the preview on the google book is limited, you can do searches and get a sentence or two. For example, I did a search on pH and per the reaction on page 444, the comment is that for pH below 5 the HOCl disportionation into chlorate and chloride is faster than hypochlorite at pH above 11.

Also, increasing the hypochlorite concentration increases reaction rate. The pH apparently drops as the reaction progresses.

Try this Link:

http://books.google.com/books?id=dXn3aB1DKk4C&pg=PA247&a...

Also, doing a search (remember to first click "Clear Search" in the upper right of the text box) on NaOCl produced the added info on the overall reaction:

2 HOCl + NaOCl --> NaClO3 + 2 HCl

and the slower hypochlorite reactions at high pH proceed as follows:

2 NaOCl --> NaClO2 + NaCl

NaOCl + NaClO2 --> NaClO3

Link:

http://books.google.com/books?id=dXn3aB1DKk4C&pg=PA247&a...

Also, searching on 'Chlorine' I found the comment that "The ratio of hypochlorous acid to hypochlorite ion increases with decreasing pH until 5.5".

Today, the practice of using excess Chlorine on hypochlorite to create chlorates is actually akin to the hypochlorous method, as one source states:

"The hypochlorites are decomposed at ordinary temperatures, with loss of bleaching power, by excess of hypochlorous acid, the products being a chlorate and a metallic chloride. (Balard.) This decomposition is produced with even greater facility by the addition of free chlorine to the hypochlorite: part of the metallic oxide is then converted into chloride— while the hypochlorous acid is liberated, and, at the same time, a fresh quantity of it is formed by the combination of part of the chlorine with the oxygen of the metallic oxide. (Gay-Lussac.)"

Source: The Hand-book of chemistry, Volume 2 by Leopold Gmelin, 1849, page 301.

LINK:
http://books.google.com/books?pg=PA304&dq=iron+hypochlor...

Note, I previously noted, the action of NaClO on dilute Chlorine water, produces HOCl so the action of Chlorine on a dilute solution of NaClO will also form HOCl. However, if the solution becomes too acidic, the available HOCl declines.

[Edited on 1-1-2012 by AJKOER]

[Edited on 1-1-2012 by AJKOER]

idea-man - 27-3-2016 at 15:56

Woelen ... Thanks for your Post, and others about ClO2.

I've been making ClO2 because of my interest in MMS. I've discovered that the MMS method, acidified sodium chlorite, is the worst way to make ClO2. It only produces a maximum of 35% initially, meaning it first produces HClO2, chlorous acid. Then the HClO2 decomposes into ClO2. And you can't ingest it, because the leftover and byproduct make you sick. So I use a different method.

I have about a half dozen formulas, mostly from industry sources in ClO2 generation for the food processing companies.

There's two methods for the alkaline-acid generation that you investigated with calcium hypochlorite.
(1) the bleach is added to the acid: NaOCl + HCl = HOCl + NaCl
then the sodium chlorite is added: 2 NaClO2 + HOCl + HCl = 2 ClO2 + H2O + 2 NaCl

(2) the sodium chlorite is added to the acid, first: HCl + NaClO2 = HClO2 + NaCl to make chlorous acid
then the bleach is added: 2 HClO2 + NaOCl = 2 ClO2 + NaCl + H2O
===

About the brown color, from your website, I've seen that in an MMS book. The whole mixture turned brown, but only briefly before turning yellow. As far as I've seen, that only happens when using HCl, not citric acid, for instance.
Do you have an idea about what that color is, as ClO2 doesn't seem to ever be described as that dark?
===

I just made some ClO2, yesterday, with NaClO2 and vinegar. Because of your Post, I tried pouring a little Clorox into it. I was surprised at how dark the yellow color got. It was actually gold colored, the same as the formula I use. That formula is being used by a Japanese product, because it goes to near 100% completion.

Bob

gatosgr - 28-3-2016 at 00:20

What is MMS and what japanese formula are you talking about?