sodium polysulfide
sreenath
I came across the following method to prepare sodium sulfide (in
solution) in a old CRC handbook of physics and chemistry.
"Dissolve 480 grams of Na2S 9H2O in 500 ml of water, add 40grams of
NaOH and 18 grams of sulfur.Stir thoroughly and dilute to 1 liter with
water"
Considering that we add just a small quantity of sulfur (18 g), will
there be a large quantity of unconverted monosulfide? Would adding
larger quantity of sulfur help?
If NaSX is the formula for sodium polysulfide, where X is a number,
from the above preparation, what would be the typical value of X?
Can it be as high as 4 or 5, or is it more likely in the range of 2-3?
Also, could someone provide a equation for the above chemical
reaction?
If anyone knows a better method for preparing sodium polysulfide,
please post it.
Thanks in advance,
Sreenath
Zinin
>solution) in a old CRC handbook of physics and chemistry.
>
>"Dissolve 480 grams of Na2S 9H2O in 500 ml of water, add 40grams of
>NaOH and 18 grams of sulfur.Stir thoroughly and dilute to 1 liter with
>water"
Among other things, Na2Sx is used for the Zinin reduction of nitro to amino.
There are other (similar) preps in Org Syn (orgsyn.org).
>If NaSX is the formula for sodium polysulfide, where X is a number,
>from the above preparation, what would be the typical value of X?
>
>Can it be as high as 4 or 5, or is it more likely in the range of 2-3?
The common preps for Zinin reduction have been characterized as mixtures
but I don't recall the values of X. However, phys org chemists have claimed
to have preps that allow the isolation of decent amounts of relatively pure
Na2Sx where x has a single value (in the 2-7 range, as I recall). For Zinin,
the mixtures are fine.
>Also, could someone provide a equation for the above chemical
>reaction?
I'd just picture it as nucleophilic attack of NaSS(-) on S8 to get
Na-SS-SSSSSSSS(-) or Na-SS-SSSSSSSS-Na followed by another
attack by Na-ss(-) or Na-SS-SS...S(-) somewhere along the chain
to produce the shorter fragments: Na-SS-SSS(-) + Na-ss-SSSSS(-) ,
etc. Another possibility is internal attack by terminal S(-) to form
cyclo-Sn + Na-SS-S(8-n)-Na.
--
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Wilco Oelen
As a photographer, I once made a solution of a polysulfide as follows:
1) Dissolve some sodium sulfide in water. I used technical sodium
sulfide, yellow flakes, deficient in water, with approximate
composition Na2S.3H2O. I don't know the exact concentration, but it
was fairly concentrated, but not as much as you give in your
description above.
2) Add some elemental sulphur.
3) Heat for several minutes. The sulphur dissolves, but it is a slow
reaction. I could dissolve quite some sulphur in the liquid. It
becomes bright yellow at first, when more sulphur dissolves it becomes
brown/yellow. The heating is important. Without heating the reaction
hardly proceeds.
Adding a pich of NaOH may help reduce the smell of the liquid and may
speed up the rate at which the sulphur dissolves, but first try
without. If NaOH is present, then elemental sulphur disproportions to
sulfide and thiosulfate: 4S + 6OH(-) --> 2S(2-) + S2O3(2-) + 3H2O. The
sulfide can react further with sulphur, but the thiosulfate may be a
side product which you don't want. You even get some, without addition
of NaOH, because Na2S is very alkaline in solution on its own already.
I think that all kinds of polysulfides are formed, ranging from
S2(2-) to S5(2-), together with some thiosulfate. Probably also S(2-)
still is in the solution. This method was OK for me, I needed a
polysulfide solution for toning a print and it worked OK. Using this
method, however, it is very hard to get well-defined solutions, which
only contains Sx(2-) species for a single value of x.
Right now, I don't prepare polysulfides anymore myself. You can buy
potassium polysulfide from chem suppliers and also from well-equipped
photo-suppliers (I have good experience with
http://www.artcraftchemicals.com and http://www.colba.net/~fotochem/,
who ship internationally many items). So, if you don't care for the
sodium being replaced by potassium, then this may be a better option.
The stuff you can buy, I was told, has approximate composition K2S3,
but I never checked that. It simply works OK for me.
Wilco
Dirk Bruere at Neopax
Wilco Oelen wrote:
When I was a kid I simply dissolved sulphur in conc hot NaOH soln.
No need for NaS as a starting point.
--
Dirk
The Consensus:-
The political party for the new millenium
http://www.theconsensus.org
sreenath
Thanks for all those who replied.
Actually, I also need this for preparing brown toner for photographic
paper. I prepared sodium sulfide in another way(an old book by Clerc
provided the method).
I first desolved Na2S in water and heated it, and when it was close to
boiling, added sulfur powder and the sulfur completely dissolved. The
solution was orange in color. It is able to tone warm tone papers
quite well.
I live in India, where potassium polysulfide(aka liver of sulfur, etc)
seems to be unavailable. I am surprised, since this seems to be used
for lot of other purposes as well. So, I have no option but to prepare
this myself.
I could not understand why NaOH was needed, since Na2S and sulfur
seems to work well.
-Sreenath
Wilco Oelen
>
> Actually, I also need this for preparing brown toner for photographic
> paper. I prepared sodium sulfide in another way(an old book by Clerc
> provided the method).
>
> I first desolved Na2S in water and heated it, and when it was close to
> boiling, added sulfur powder and the sulfur completely dissolved. The
> solution was orange in color. It is able to tone warm tone papers
> quite well.
I tone prints in that way with polysulfide toners. If you have a
polysulfide solution, then toning can be done by simple immersion. The
extra sulfur on the polysulfide ions is perfectly capable of reacting
with the metallic silver in the print to form brown silver sulfide,
which covers the black silver, resulting in a nice dark brown print.
The solution may need some heating in order to do so.
Toning with a simple sulfide solution also works. In that case,
however, the silver must be oxidized prior to toning to Ag(+). An
halogen compound must also be present in the solution, in order to
avoid motion of the silver ions and blurring the image. If the print
is oxidized by a potassium ferricyanide/potassium chloride or
potassium ferricyanide/potassium bromide mixture, then after good
rinsing, it can be toned quickly with a plain sulfide solution. The
print will become lighter in that case, more like sepia/brown. This is
because now all silver is first converted to silver halogenide and
that in turn is converted to silver sulfide.
>
> I live in India, where potassium polysulfide(aka liver of sulfur, etc)
> seems to be unavailable. I am surprised, since this seems to be used
> for lot of other purposes as well. So, I have no option but to prepare
> this myself.
>
> I could not understand why NaOH was needed, since Na2S and sulfur
> seems to work well.
The NaOH causes the reaction to go faster. The disproportionation of
sulfur to sulfide and thiosulfate is faster than attachment of
elemental sulfur to sulfide ions. As a side effect, a large part of
the sulfur can also attach to already existing sulfide ions (remember,
sulfur exists as S8, hence when a few atoms are used in the
disproportioning reaction, the other atoms also become available for
reaction). However, as I said in the previous mail, when using NaOH
you also have more unwanted thiosulfate. What happens precisely in
this reaction by no means is clear. It is a very complicated reaction
and the equation, I gave in the previous posting is a highly
simplified. As another poster mentioned already, many side reactions
occur.
I also did quite some research on how to do photography with easy to
obtain chemicals for low prices. I made a toner, allowing all kinds of
colors between which can be made from mixing yellow, blue and brown.
E.g. greens can be obtained by mixing yellow and blue, nice brownish
tints can be obtained by mixing brown/sepia with yellow. Olive green
can also be obtained. All these colors can be obtained by using easy
to obtain chemicals (hopefully also in India). The toner is described
at
http://www.woelen.nl/photo/toner.pdf
I hope you will find this interesting.
Wilco
>
> -Sreenath
sreenath
> How did you do the toning? Simply immersing the print in the solution?
> I tone prints in that way with polysulfide toners. If you have a
> polysulfide solution, then toning can be done by simple immersion. The
> extra sulfur on the polysulfide ions is perfectly capable of reacting
> with the metallic silver in the print to form brown silver sulfide,
> which covers the black silver, resulting in a nice dark brown print.
> The solution may need some heating in order to do so.
> Toning with a simple sulfide solution also works. In that case,
> however, the silver must be oxidized prior to toning to Ag(+). An
> halogen compound must also be present in the solution, in order to
> avoid motion of the silver ions and blurring the image. If the print
> is oxidized by a potassium ferricyanide/potassium chloride or
> potassium ferricyanide/potassium bromide mixture, then after good
> rinsing, it can be toned quickly with a plain sulfide solution. The
> print will become lighter in that case, more like sepia/brown. This is
> because now all silver is first converted to silver halogenide and
> that in turn is converted to silver sulfide.
>
I used copper sulfate and ammonium chloride as bleach. Later I
switched over
to potassium ferricyanide/potassium bromide as bleach.
I wanted a single bath toner and found that
polysulfide works. However, as I said earlier, this
particular chemical is not available in India. That is
when I made my own by reading old photo books.
The tone using bleach/redevelop scheme gave very yellowish
prints (on wark tone paper), which I did not like, whereas with
neutral tone RC papers the tone was acceptable.
The polysulfide toner gives much better tones (dark browns) even
with warm tone paper(Ilford MG warmtone).
Thanks for the toner formula using vanadium pentaxide. I hope to make
this sometime in future. Vanadium pentaxide is available here.
Would you be having a formula for making Selenium toner using sodium
selenite?
BTW I sent you an email reply, but that bounced.
-Sreenath
Wilco Oelen
> I had used Thiourea toner before. This needs the print to be bleached.
> I used copper sulfate and ammonium chloride as bleach. Later I
> switched over
> to potassium ferricyanide/potassium bromide as bleach.
>
> I wanted a single bath toner and found that
> polysulfide works. However, as I said earlier, this
> particular chemical is not available in India. That is
> when I made my own by reading old photo books.
>
> The tone using bleach/redevelop scheme gave very yellowish
> prints (on wark tone paper), which I did not like, whereas with
> neutral tone RC papers the tone was acceptable.
http://www.jackspcs.com/tpt.htm
It describes a thiourea toner, with some sort of color control. Color
can be controlled from yellowish to dark brown/purple. I tried this
and it gave nice results. One can vary the ratio to hydroxide and
thiourea in a solution. The more thiourea, relative to hydroxide, the
more brown the color becomes. This is what the site describes. Really
worth trying. However, it is a two-bath toner, with a
pre-bleach/oxidation step.
>
> The polysulfide toner gives much better tones (dark browns) even
> with warm tone paper(Ilford MG warmtone).
Yes, as I already explained, because this toner covers metallic silver
with brown silver sulfide.
>
> Thanks for the toner formula using vanadium pentaxide. I hope to make
> this sometime in future. Vanadium pentaxide is available here.
>
> Would you be having a formula for making Selenium toner using sodium
> selenite?
I'll look for such formulae. I have some old books on photo-chemistry.
However, I must say, that I have never worked with sodium selenite.
> BTW I sent you an email reply, but that bounced.
I sent a private e-mail to you already, which you can reply. The
address, used for posting at sci.chem is spammed too much and I shut
it down recently.
>
> -Sreenath