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Organikum
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aromatic sidechainchlorinations - Toluene - Benzylchloride, Benzalchloride, Benzotrichloride and followup reactions yielding Benzaldehyde and Benzoic
Acid. Polverone bonus: Chlorination of Acetic Acid
Long title, short post.
Wellknown are the usual methods to chlorinate the sidechain of toluene by Cl2 and light, by Cl2 and PCl3 and by bleaching powder (hypochlorite, Loomis
patent).
Wellknown are also the methods for producing benzaldehyde and benzoic acid from benylchloride, benzalchloride and benzotrichloride.
Wellknown are also the problems regarding ringchlorination as these ringchlorinated compounds are almost not to remove from endproducts in
completeness - this being a problem in special in the case of benzaldehyde.
Now I pick up the case of benzaldehyde and present a way to produce this compound from toluene via the sidechainchlorinated compounds benzyl and
benzalchloride whereby ringchlorination is avoided and up to no benzoic acid is formed as byproduct.
Reference: US2817632
This patent claims that a small amount of hexamine added to the reaction avoids ringchlorination and deactivates eventually present catalysts which
would promote this ring-chlorination, Fe and other heavy metal ions etc. The amount of hexamine to add comes from 0,1% w/w to 10% w/w.
Nice. Use toluene from the paintthinnercan as is.....
Better even: If chlorinating toluene you unavoidable end up with a mixture of mono-di-and-tri-chlorinated compounds. Temperature control helps but the
best way is control of temperature and a large excess of toluene. Keep it on the lower side you will end up with a mixture of mono and di-chlorinated
toluene - benzylchloride and benzalchloride. Now you want to get benzaldehyde - what to do?
Ullmann 2002:
Boiling a mixture of benzyl and benzalchloride in an aqueous solution of hexamine yields - benzaldehyde.
And here the ring closes - add hexamine to avoid ringchlorination and add more hexamine in water to get benzaldehyde which is to be called free from
ringchlorinated impurities, good enough to be used in biosynthesises or similar.
And the Polverone special:
US3691217
Benzalchloride and acetic acid plus tin(II) or tin(IV) chloride yields benzaldehyde and chloroacetic acid.
[Edited on 8-11-2004 by vulture]
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Polverone
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Beautiful!
What a marvelous aid to the DIY production of benzaldehyde, benzyl alcohol, and chloroacetic acid! Now I just need to see who I can find to sell me a
cylinder of Cl2 
PGP Key and corresponding e-mail address
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Nick F
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I think we should all stop for a moment and just consider how wonderful hexamine is.
Thanks Organikum  .
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Organikum
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One big advantage of the described way to benzaldehyde is in my eyes that the synthesis avoids the distillation of the chlorinated compounds -
benzylchloride at least is an evil lachrymator worse than chloroacetone for example.
The suggested way to do this would be:
- gently chlorinate the toluene at low temperatures - I actually would try to stay below the boiling point of the reaction mixture, using a 500W
halogen as lightsource and a thin walled flask. The chlorine has to be as free from oxygen as possible. Also the tolune should be gently boiled before
use to remove dissolved O2. Minimal amounts of red phosphorus are told to to drive the reaction forward - even some matchbox striking pads will work.
(dont forget the hexamine - yep)
- after a certain amount of chlorine was taken up - what can be determined by weighing the flask, bubble air through the reaction mixture to
remove/destroy the excess Cl2 present, then distill out most of the toluene (a short column is favorable but by no way a must have here) and add a
good excess of hexamine in water solution and boil the shit outa the soup under reflux.
- After some time shut down the reflux and collect what comes over with the steam - this will be benzaldehyde and toluene.
(benzylchloride can be steamdistilled too I was told, but after my best of knowledge this wont happen as long as toluene and benzaldehyde are present,
at least those will come first.
It should be easy to determine when the reaction hexamine-benzyl/benzalchloride is completed: As soon the vapors stop to make you cry and sick it´s
done.
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Organikum
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The good Ullmanns was a little short in explanaition of the Sommelet procedure.
Just boiling the benzyl/benzalchloride mixture with aqueous hexamine is not right.
Here is it right:
US4321412
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EXAMPLE 1,050.1 g of chlorinated p-xylene, consisting of 47.61% of p-xylyl chloride, 43.76% of p-xylene, 3.6% of nuclear-chlorinated p-xylene and
5.03% of polychlorinated p-xylenes, the mixture containing exactly 500 g (3.55 moles) of p-xylyl chloride, are stirred with 546.7 g (3.9 moles) of
urotropin for 15 minutes, under nitrogen, in a 4 liter three-necked flask equipped with a reflux condenser and stirrer. 1,000 g of water are then
added and the mixture is refluxed for 3 hours. It is then allowed to cool, brought to a pH of 3-4 at room temperature with 170 ml of concentrated HCl,
and then refluxed for a further 15 minutes. Thereafter, the mixture is allowed to cool again and the aqueous phase is separated off. The organic
phase is distilled after addition of 0.01 g of hydroquinone.
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The other patent describing the addition of hexamine to prevent ringchlorination is US2817632
[Edited on 12-5-2004 by Organikum]
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cavgdad
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gently chlorinate?
which method of chlorination are you suggesting? or do you prefer?
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Prince_Lucifer
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Chlorination of toluene
Organikum is clearly and obviously stating that the Photo-Catalyzed Chlorination of toluene be utilised, hence the 500W halogen light!
Right, now that is settled:
Organikum my friend, how are you?
I am well, i am also intrigued by the information you have just posted.
Swim has recently decided to shun the Ca(OCl)2 chlorination due to safety concerns and by-product formation that the reaction is unfortunately
notorious for!
Swim would like to pursue the method you have outlined, however he needs clarity.
Now, swim is clear on the chlorination aspect of things, however he is unsure of the amount of hexamine to use.
In the example provided, i assume the amount of hexamine used is in relation to the amount of by-products in the flask.
Since swim does not have the means to analyze the contents of a flask, he considers it difficult to measure the amount of by-products as a percentage.
Say for example, 100g of toluene was chlorinated thouroughly.
Now in theory, after the necessary distillations have been completed, then the final yield of Benzyl Chloride should be around 100g. Now this example
is just to demonstrate how much Benzyl Chloride should be available.
Seeing as swim have never performed this reaction, he havs no idea as to how much Benzal Chloride or other by-products are in the solution. Anyways:
What amount of hexamine would you suggest to add to a solution of this calibre?
You say benzaldehyde and toluene will come over with the steam after reflux is stopped.
After initial distillation to seperate these two compounds, would you suggest redistillation, perhaps under vaccuum to purify the benzaldehyde, or
would it be suitable for a bio-synth as is?
Org, can you suggest a 'safer' way to estimate when the initial reaction with hexamine is completed?
Swim may wear a tactical gas mask so unfortunately he wont be able to sample the delightful aromas of Benzal/Benzyl Chloride!
Thankyou.
[Edited on 15-5-2004 by Prince_Lucifer]
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Organikum
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Answers and a goodie....
Actually it has shown that it makes no sense to go for a mixture of benzyl and benzalchloride, but it is better to chlorinate the toluene until mostly
benzalchloride is formed with benzotrichloride as impurity.
This point of chlorination can be determined either by weighing the receiving flask or easier by the boiling point. When the thermometer shows the
refluxing solution has reachewd 185°C it is done. The mixture should contain now about 80% benzalchloride.
Basic hydrolysis with sodium carbonate will transform the benzalchloride into benzaldehyde and the benzzotrichloride into benzoic acid which can
easily separated as its salt.
The addition of 0.1% to 0,3% hexamine to the toluene inhibiting ringchlorination is a winner. The Sommelet - BzCl to b-dehyde by hexamine - works well
but is uneconomical because of the amounts hexamine needed.
And the goodie:
Toluene can be chlorinated by TCCA, trichloroisocyanuric acid (swimming pool supply) and a radical initiator under acidic conditions. The radical
initiator named in the article was benzoylperoxide, red phosphorus or UV might work too. Without radical initiator mainly ringsubstituted compounds
are formed.
This reminds on a experiment on the chlorination of toluene by TCCA and light I read about but never got it working although I tried it several
times..
But lets fuse things together now:
- What about either using benzoylperoxide in the usual chlorination, instead of red phosphorus in addition to the light?
- What about adding a dash of hexamine to the toluene and doing the chlorination with TCCA and benzoylperoxide to avoid the ringchlorination (bright
light wont hurt for sure) ?
I will give it a try.
ADDOON: benzoylperoxide (or dibenzoylperoxide whats interchangeable here) is found as activator for polyester resin in every automobile supply shop.
You will have to buy it together with the polyester resin probably, this contains at least 40% styrene - not bad too, isnt it?
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Mendeleev
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I am sort of new to synthesizing chloroaromatics, but the benzyl chloride synthesis interests me. I was looking at the article on rhodium http://www.rhodium.ws/chemistry/benzylchloride.html and the two methods that interest me are the photo-catalyzed chlorination of toluene, and the
calcium hypochlorite method. I had some question about the photo-chlorination procedure, namely how important is the calcium chloride tunnel
described in the article, and what is the deal with the sodium hydroxide wash bottles? I was thinking, could you just boil the toluene while a gas
generator pumps Cl2 under a 2 million candle power bulb? Also it says to distill under reduced pressure, will normal pressure not work or is it too
slow? As far as the calcium hypochlorite method goes, their description was very vague. It says mix equal volumes of toluene and hypochlorite and
heat to 105 C, but it gives no details for extraction, and I'm not sure about measuring solids by volume. Would you just distill it for
extraction? What is the reaction anyway: 2C7H8 + 1Ca(ClO)2 ---> 2C7H7Cl + 1Ca(OH)2?
[Edited on 13-6-2004 by Mendeleev]
[Edited on 13-6-2004 by Mendeleev]
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
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Organikum
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Download Vogels 3rd from our ftp or from Rhodiums page and look for the sidechainchlorination of toluene there. You should find it under
"aromatic chlorinations" I think.
There is everything better explained as any of us probably can do.
ORG
For the hypochlorite method go to the HIVE
https://www.the-hive.ws
and do a search for "loomis" and one for "benzylchloride toluene" and you will find what you want to know.
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Mendeleev
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What is the ftp address, I couldn't find a link or the actaul address anywhere on the forum despite searching for half an hour. The info on the
hive was good though, thanks.
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
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Mendeleev
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Just to clarify my earlier post, I found out that equal masses of toluene and calcium hypochlorite are used. This means the reaction doesn't go
to completion, but the main product is benzyl chloride, by about 30% and the rest is unreacted toluene. The reaction has to be heated but can't
be heated above 105 degrees C or it will explode, so a boiling water bath is perfect to keep the reaction about 95-100 degrees C. Once the reaction
finishes the toluene bp (108-112) is distilled off and the benzyl chloride (bp 179) is distilled after all the toluene is distilled off. A vacuum is
not necessary for distillation, but helps. As no one has told me the address of the ftp, I have one question left, were the wash bottles described in
rhodium's page just for keeping the mixture dry or what?
[Edited on 15-6-2004 by Mendeleev]
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
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Organikum
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You might consider to look in "Forum Matters" for information about the forum-ftp.
If you dont provide better information or a direct link you wont get any answers. I am not going to invest my time to search through Rhodiums page for
the tidbit of information you hinted at.
Please dont regard me as inpolite but try to see it from my point of view. Altough I CAN read other peoples thoughts I RARELY do so as it hurts me
always badly - its so damned messy and often conflicts with my own mental diseases, ya know?
ORG
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Mendeleev
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I did provide a direct link, see my first post in this thread .
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
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Organikum
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Huhh, I overlooked it.
The washbottles refer to the photocatalyzed chlorination of toluene by Cl2 and are necessary for cases of suckback.
And: Yes they ARE necessary.
Look in the Vogels 3rd. thats a much better source for information than any webpages. This book can be dl from Rhodiums page or from the forums ftp as
OCR-pdf whats preferable. Thanks Polverone and Mephisto.
[Edited on 16-6-2004 by Organikum]
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Mendeleev
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I downloaded Vogel's Third Edition in pdf, it is my holy book now. I also realized the passage in Rhodium on photochlorination is directly from
Vogel's Third Edition. The photochlorination method interests me in the long run, but for starters I would like to try the calcium hypochlorite
method.
In the loomis thread on the hive, somebody began to doubt the safety of the reaction because it required anhydrous or nearly anhydrous products.
However after a bit of searching I found that calcium hypochlorite is non-hygroscopic and decomposes readily to hypochlorous acid in water. So you
should have no problem with water absorption and even if some gets in it will not stay for long, but will decompose into hypochlorous acid. The
toluene I get at the store is labeled as 100% so that takes care of that.
Also the pool calcium hypochlorite says it has 65% available chlorine. Hoping this does not mean it is 65% I did a few calculations and found that
calcium hypochlorite is 49.xxx % chlorine by mass, but that the decomposition product, calcium hypochlorite, which is more relevant to pools, is 67%
chlorine. So hopefully 65% available chlorine means its >97% calcium hypochlorite, right? Oh and I'm hoping that this site that says the 65%
available chlorine calcium hypochlorite is only 67% is just a typo.
http://www.hydropool.com/cgi-bin/hydro/chemicals/pool/biogua...
[Edited on 19-6-2004 by Mendeleev]
[Edited on 19-6-2004 by Mendeleev]
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Organikum
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Pool-Shock is pure calcium hypochlorite. Important is that it contains no water. The "available chlorine" is not on the point here, just
forget it.
I would suggest to use the chlorination though. The hypochlorite method is not so good for making benzalchloride as it is for making benzylchloride.
This is based on the amounts of hypochlorite needed. If the toluene doesnt cover the hypochlorite completely you will get an explosion.
I tried this lately and I will not do it again although I had no explosion. At least no big one.
If you want to use the hypochlorite pathway you should only chlorinate to benzylchloride and use the Sommelet with hexamine to convert this to
benzaldehyde as described in my first post.
If you want benzalchloride which is more easy converted to benzaldehyde by just running it into a slurry of chalk in water whilst stirring strongly
you should use the chlorination as described in Vogels 3rd.
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Mendeleev
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My goal is neither benzal chloride nor benzaldehyde, at the moment, right now I am trying to get benzyl chloride so I guess I am fine for now. Is
this the pool shock stuff you mentioned Organikum?
http://www.intheswim.com/catalog.cfm/dest/dept/deptid/38/sto...
The pool shock says its 68% calcium hypochlorite and the super pool shock says just calcium hypochlorite, I gues you were talking about the super
stuff?
Also is this brand reasonably pure?
http://www.poolandspa.com/catalog/product001090000120.cfm
[Edited on 19-6-2004 by Mendeleev]
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Organikum
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I dont know this, I dont live in the US and never tried these brands.
The Super-Pool-Shock sounds best to me though.
Try to get the MSDS data sheet.
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Mendeleev
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This is a nightmare, I went through 15 US pool suppliers and 3 UK suppliers, and the highest they have 65-73% calcium hypochlorite. The rest they say
is soluble salts. Will the reaction work with 73% material, provided its anhydrous? After all as the reaction goes along, the calcium hypochlorite
is converted into the chloride, hydroxide, and etc.
Edit: Even the goddamn science supplier http://www.sciencelab.com sells it as 65% and they have a very good selection.
[Edited on 20-6-2004 by Mendeleev]
[Edited on 21-6-2004 by Mendeleev]
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Organikum
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I guess it will work, but guessing says not knowing for sure......
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Polverone
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a possible safety consideration
I wish I could check the Hive for that patent, but I never do that while at work (even on lunch). Wasn't the patent from, say, before 1940? I
believe high-test-hypochlorite was rare or unkown as a commercial product at the time of the patent's writing. The "bleaching powder"
referred to probably had a considerably lower chlorine content than modern pool shock treatments. For example, a JACS article from 1933, "Action
of Bleaching Powder on Ketones," begins the experimental section with "Three hundred grams of commercial bleaching powder (24% available
chlorine) was made into a paste with 750 cc of water at 15 degrees C." Also, from Ullman's, referring to more modern products: "The
following qualities of solid hypochlorites are available (content of available chlorine, wt %, in parentheses): tropical bleach (34 – 35), bleaching
powder (35 – 37), and high-percentage hypochlorite (70)."
I'm a bit alarmed at the idea of heating toluene with the most potent calcium hypochlorite available, given the exothermic nature of the
reaction.
PGP Key and corresponding e-mail address
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Mendeleev
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Here's the patent, straight from the hive.
Be it known that I, CHAUNCEY C. Loomis, a citizen of the United States, residing at Syracuse, in the county of Onondaga and State of New York, have
invented a new and Improved Process of Chlorinating Toluene, of which the following is a specification.
My invention relates to the chlorination of toluene with consequent production of benzyl chlorid and its related products, benzal chlorid and benzo
trichlorid. This has heretofore been accomplished by passing chlorin gas through boiling toluene and also by admitting to a mixture of toluene and
bleaching powder an acid gas to decompose the bleach with liberation of nascent chlorin.
Both these processes are subject to objections, the former because of the difficulties incident to handling the chlorin and the production of
by-products of little value which are not readily separable from the product desired and the latter by reason of the inconvenience of generating and
applying the acid gas and the gumming up caused by its reaction with the bleaching powder in the toluene. I have discovered, however, and my invention
broadly stated consists in the application of the fact, that by heating to a high temperature an anhydrous mixture of toluene and bleaching powder,
with thorough commingling, and without the use of any acid, the chlorination of the toluene is effected without any of the disadvantages incident to
the processes above referred to. In the absence of any added water the chlorin from the bleaching powder seems to go directly to produce benzyl
chlorid in the side chain without attacking the nucleus, even though the process is carried on in the presence of iron, as in an iron vessel.
In carrying my invention into effect, dry bleaching powder (calcium hypochlorite, or other equivalent hypochlorite,) and toluene are mixed in
proportions varying according to the extent of chlorination desired. For example, 200 kilograms of toluene are heated, as in a steam jacketed iron
mixing kettle to a high temperature, say 90°. Dry bleaching powder is then slowly added to this, the temperature being gradually raised until it
approximates the boiling point of toluene, which, of course, cannot be exceeded. When 200 kilograms of bleaching powder have been added the mixture is
held at the high temperature attained, (i. e., to secure the best results, from 100° C. to 105° C.) for about one hour, or, until the reaction is
effected, with continuous thorough mixing. The escape of toluene vapor during the operation may be prevented by means of a reflux condenser fitted to
the mixing vessel.
The resulting mixture is then cooled down and allowed to settle and as much oil as possible is siphoned off from the top. The oil left adhering
to the lime residue is then removed by steam distillation and added to that siphoned off. In this way 200 to 210 kilos of oil are obtained, having a
specific gravity of .910 to .960 at 20° C. and containing from 30 to 35 per cent. of benzyl chlorid and from 70 to 65 per cent. of toluene. These can
then be separated by fractional distillation. A higher percentage of chlorinated product can be obtained by using a greater proportion of the
bleaching powder. In this case, however, some benzal chlorid and benzo trichlorid will be formed. Or, if desired, sufficient bleaching powder may be
added to convert all the toluene directly to benzal chlorid and benzo-trichlorid and the resulting mixture of lime and the chlorids can be converted
into benzaldehyde and benzoic acid by boiling with water.
Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:
1. The process of chlorinating toluene which consists in heating together an anhydrous mixture of toluene and bleaching powder without other
admixture.
2. The process of chlorinating toluene which consists in heating together toluene and dry bleaching powder in the absence of acid.
3. The process of chlorinating toluene which consists in heating together toluene and dry bleaching powder in the absence of acid or other agent for
decomposing the bleaching powder.
In testimony whereof I have affixed my signature, this 15 day of October, 1917.
CHAUNCEY C. LOOMIS.
You're right it does say bleaching powder! So I might even have to use a lower mass of pool hypochlorite? If you could find out for sure what
percent was available in those days, that would be awesome.
[Edited on 21-6-2004 by Mendeleev]
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
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Mendeleev
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According to this link:
http://www.intox.org/databank/documents/chemical/calchypo/ci...
bleaching powder is 35-37% hypochlorite and that the commercial 65-70% product is the dihydrate thus unfit for chlorination of toluene. However it
says that it is also available as 75-80%, would this be anhydrous? If so the 73% super pool shock on the "in the swim" link I posted
earlier would be good for the reaction.
Trogdor was a man. A dragon man. Or maybe just a dragon. . .
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Polverone
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Ullmann says:
"High-Percentage Hypochlorite. Solid hypochlorites with 70 % and higher available chlorine contents can be prepared by
chlorinating slurries of such calcium compounds as calcium hydroxide, or bleaching powder. Initially, hemibasic calcium hypochlorite, Ca(OCl)2· 1/2
Ca(OH)2, is formed. When further chlorinated, this gives neutral calcium hypochlorite dihydrate, Ca(OCl)2 · 2 H2O, which is then dried to the desired
high-percentage hypochlorite."
It sounds like the water should already be gone from the hypochlorite, and that cheminfo page is confusing an intermediate with a final product. But
if you want to be sure, put 200 mg or so of calcium hypochlorite pool shock in the bottom of a test tube, heat strongly, and see if you get water
droplets in the cool portion of the tube. A dihydrate should be easy to distinguish from anhydrous or almost-anhydrous material.
Edit: from perusing old JACS articles, I would say that bleaching powder circa 1917 probably contained between 25 and 35 percent available chlorine. I
don't know if it is better to simply use less high-strength hypochlorite, or to add an inert solid to dilute it.
[Edited on 6-22-2004 by Polverone]
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