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Author: Subject: Calcium Sulphide
Tacho
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[*] posted on 10-1-2004 at 09:23


How about metallic calcium and sulfur?
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Mr. Wizard
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[*] posted on 10-1-2004 at 11:53


Metalic calcium filings and sulfur react with explosive force. Even in an open one gram pile with a long wooden match I scorched my fingers. The filings were very course. The only thing glowing afterwards were the spots in front of my eyes.
For production of phosphors try looking at:
http://www.belljar.net/content.htm
Vol 5, 1996
This is an index of some of the fantastic DIY projects this newsletter touched on. I'll try to give the highlights later if anyone is interested, as I believe it might be copyrighted material. I'm not sure what I can put on the net without his permission. I did subscribe to the newsletters for a while.
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[*] posted on 10-1-2004 at 11:55


I did that once. Bloody great red flame and burned a hole through the steel crucible. The product didn't glow in the dark.
How about H2S and Ca(OH)2, I know it's a reversible reaction but you should be able to get it to work.
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[*] posted on 10-1-2004 at 13:06


unionised,
Maybe you could try some "Dormant Disease Lime Sulfur" spray, used on fruit trees this time of the year. I think its a calcium polysufide solution, and reeks of sulfur. It is a red liquid when it's in the container, but the solution is a clear yellow color. It would be safer than making H2S. Maybe you could just add lime Ca(OH)2.?H2O and heat at 900C-1000C in a covered quartz or suitable crucible for 1 hour. Allow to cool and check. The phosphor article mentions many times how the sulfides have to be heated for this length of time and temp. Perhaps trying forming the CaS in solution and drying it before activating it by heating it.

I'd forgotten about the red flame of the Ca + S! I was more surprised at how hot it was, and the scorched fingers..:o
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[*] posted on 10-1-2004 at 14:25
Another Way


How about :
3CaSO4 + 8Al --> 3CaS + 4Al2O3

This is similar to thermite. Requires a high temperature to ignite but a vigorous reaction producing the desired product.

Hodges
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[*] posted on 14-1-2004 at 03:13


i suppose the CaS should contain some particular impurities to glow in dark..



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[*] posted on 14-1-2004 at 04:34


Do you guys just want to make calcium sulfide because its phosphorescent? or for sulfide precipitate reactions?

If the latter, I would point out this website.

http://www.crscientific.com/nh4sulfide.html

I have been wanting to prepare this reagent myself but have not got around to it. Hope this helps!
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markgollum
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[*] posted on 9-3-2009 at 20:01


I have reduced calcium sulphate to the sulphide twice. I did it by grinding together the CaSO4 + charcoal in a blender several minutes until it was thoroughly mixed, both ingredients were fine powders before they were ground together. The vessel I used was a piece of 2’’ steel galvanized plumbing pipe and end caps, one end cap had a small hole drilled in it and a small piece of alumina fiber blanket was fitted inside the cap and held in place by a bit of bent copper wire inside the end cap (to act also as a gauge at the max internal temperature buy later checking to se if the wire had melted), all the galvanized parts were stripped of zinc either by letting the parts sit in hydrochloric acid for several hours until some time after the hydrogen evolution ceased or in the case of the pipe by heating them in the open air until the zinc can be visibly seen to be boiling off and burning, the fumes are toxic so I set it up on my concrete deck and watched it from in the house through a window until I was satisfied that the bluish green flames and white smoke had stopped and there was no zinc remaining. I had initially wrapped it with one layer of alumina fiber blanket then with nichrome wire; unfortunately the ZnO dissolved the alumina blanket and severely corroded the wire. The pipe was filled with the calcium sulphate /Carbon mixture and a glass rod was pushed in through the center to produce a cored structure and facilitate the discharge of gasses, the glass rod was removed and the pipe was carefully handled to prevent the core from collapsing. I strategically put the vessel on a large split log in my wood burning stove and built a roaring fire and kept it going for about 4 hours during which the pipe glowed a bright yellow (guestimated temperature ~950C) As it was getting late, I buried the pipe in the glowing coals and went to bed. When the contents of the vessel were examined the next day, they were white and largely free of carbon with the exception of a few larger particles in the center near the core and in the section near the end where the end cap increased the diameter, the copper wire did mot melt so the peak temperature was certainly less then 184C. The white powder rapidly bubbles up H2S when a drop of hydrochloric acid is added. I originally produced the CaS in order to try to make Na2S by leaching it with sodium carbonate but I found that the yields were poor and the product was yellow from reaction with atmospheric oxygen. Also, the product I had isolated outside later liquefied when brought indoors I think this was because the hydrate I had isolated in the cold wintery outdoors was no longer stable a the relatively balmy 25 degrees or so. I used vacuum filtration and evaporated the filtrate until the bumping began to get excessive, I protected the filtrate from oxygen as much as I could by working quickly and covering the Erlenmeyer with saran wrap and cutting a small hole in the top to emit steam in the evaporation step. I tried to perform the metathesis in methanol in the hopes of getting the anhydrous Na2S as it is very soluble and methanol, I hoped that the insolubility of the calcium carbonate would drive the reaction albeit slowly. However, after several hours at close to the boiling point with magnetic stirring, followed by letting it sit for several months I obtained essentially zero yield.

I decided to post in this thread as opposed to this http://www.sciencemadness.org/talk/viewthread.php?tid=11917
one


Edit

I also was very impressed with a group 2 alkali metal + sulfur.
I burned my fingers an was seeing spots after lighting a sulfur+ Mg filings, I was very unprepared for how hot, fast, and violent it was. It seemed more so than many other mixes I have tried.

[Edited on by markgollum]
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[*] posted on 10-3-2009 at 10:23


Nice work in making CaS Markgollum.

I felt I should say something about the use of galvanized pipe for reaction vessels, however. Instead, try "black iron" or "malleable iron" pipe fittings such as used for natural gas lines. Then you won't have to deal with those nasty zinc fumes. Probably have to burn off a little oil however.
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[*] posted on 9-8-2012 at 07:02


I know I'm bringing back an old thread but I recently tried to make phosphorecent powder with Tums and sulfur powder. And it worked! I did it in open air and heated it with a small torch for a few min. It didnt work very well. It is just barely visable in a pitch black room. I have a feeling if you did it in a container and heated it more evenly it would work better.

[Edited on 9-8-2012 by Teen Chemist]
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[*] posted on 10-8-2012 at 05:37


The reaction 2 Ca(OH)2 + 4 S + O2 --> 2CaS + 2SO2 + 2H2O procedes well, although at low temps Ca(SH)2 will form. The reaction is self susteining.



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[*] posted on 10-8-2012 at 05:57


Quote: Originally posted by Poppy  
The reaction 2 Ca(OH)2 + 4 S + O2 --> 2CaS + 2SO2 + 2H2O procedes well, although at low temps Ca(SH)2 will form. The reaction is self susteining.


Really? You have tried that?




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[*] posted on 10-8-2012 at 11:39


Quote: Originally posted by blogfast25  


Really? You have tried that?


Yes. Oddly enough I was haunted into a trip of making sulfur dioxide and realized Ca(OH)2 could work as an oxidising agent, in fact in turned to be that it is a reduction agent. Anyway the reaction was extimated: Ca(OH)2 + S --> CaS + H2O + O
So extra sulphur should give:
2Ca(OH)2 + 3S --> 2 CaS + 2H2O + SO2
As it seemed, closing the container caused the reaction somewhat to halt al ambient temperature. It even glows bright when working!
The reaction slowly vanishes thus I think its necessary to push the temperature a little higher to ensure Gibbs free energy will be supportive, considering the releasing of humidity, I would put that around almost exactly the boiling point of water, 100°C.
Oxygen is a strong enough participant I am not sure aboout its need or not, though it would be surprising efficient if the reaction proceds in the absence of oxygen pondering the versatile burn of inner layers of reactant!!
At best temperatures for a continuous flow of the reaction should not exceed that of a match which was used to lit the compost.

Thx, regards
Poppy




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[*] posted on 10-8-2012 at 11:39


Quote: Originally posted by blogfast25  


Really? You have tried that?


Yes. Oddly enough I was haunted into a trip of making sulfur dioxide and realized Ca(OH)2 could work as an oxidising agent, in fact in turned to be that it is a reduction agent. Anyway the reaction was extimated: Ca(OH)2 + S --> CaS + H2O + O
So extra sulphur should give:
2Ca(OH)2 + 3S --> 2 CaS + 2H2O + SO2
As it seemed, closing the container caused the reaction somewhat to halt al ambient temperature. It even glows bright when working!
The reaction slowly vanishes thus I think its necessary to push the temperature a little higher to ensure Gibbs free energy will be supportive, considering the releasing of humidity, I would put that around almost exactly the boiling point of water, 100°C.
Oxygen is a strong enough participant I am not sure aboout its need or not, though it would be surprising efficient if the reaction proceds in the absence of oxygen pondering the versatile burn of inner layers of reactant!!
At best temperatures for a continuous flow of the reaction should not exceed that of a match which was used to lit the compost.

Thx, regards
Poppy




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[*] posted on 10-8-2012 at 14:51


Quote: Originally posted by Poppy  
The reaction 2 Ca(OH)2 + 4 S + O2 --> 2CaS + 2SO2 + 2H2O procedes well, although at low temps Ca(SH)2 will form. The reaction is self susteining.


Per Wikipedia (I believe this comment as I have heard similar remarks on the creation of Aluminum Sulfide), to quote:

"Milk of lime, Ca(OH)2, reacts with elemental sulfur to give a "lime-sulfur", which has been used as an insecticide. The active ingredient is probably a calcium polysulfide, not CaS.[1]"

Alternately, may I suggest the following odorous path:

H2S (g) + CaCl2 (s) ---> CaS (s) + 2 HCl (g)

In words, generate Hydrogen sulfide (caution: a very toxic gas) and pass over heated CaCl2 and lead the exhaust gas into NH3/H2O2, or a large quantity of liquid bleach. Basis, to quote Wiki: "Hydrogen sulfide reacts with metal ions to form metal sulfides, which may be considered the salts of hydrogen sulfide."

[EDIT] Those working with H2S should certainly use appropriate safety equipement and ventilation. To quote Wiki: "Hydrogen sulfide is considered a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system is most affected. The toxicity of H2S is comparable with that of hydrogen cyanide. It forms a complex bond with iron in the mitochondrial cytochrome enzymes, thus preventing cellular respiration." ...."Treatment involves immediate inhalation of amyl nitrite, injections of sodium nitrite, inhalation of pure oxygen, administration of bronchodilators to overcome eventual bronchospasm, and in some cases hyperbaric oxygen therapy". In my opinion, important aspects of this gas are its high toxicity, ability to deaden nasal detection after initial exposure, delayed mortality effect and toxic exposure via skin absorption also.


[Edited on 11-8-2012 by AJKOER]
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[*] posted on 10-8-2012 at 17:14


Indeed some polysulfide may form, but the specif description for lime-sulfur involves reaction in a vessel of water! Plus sulphur is added largely in excess (3,9 to 1, whereas the described reation with lime makes use of a 3 to 2 fraction)
Certainly, we may put to press, additional purification is necessary. CaS being such a hard material, in meaning so by having a high boiling point and low solubility (its said it decomposed by water, but it is not mentioned how fast), you couldn't think of it as being perfectly rounded equimolar interstices of calcium and sulphur. But we may be impressed wrongly, by the rearrangement is so strong, the reactive area glows bright! Although possibily not many energy escapes.

Think now of calcining calcium hydroxide and putting to react with sulphur, would this proceed aswell?
2CaO + 3S --> 2CaO + SO2
Maybe heating the product of the later reaction with the lime would sublime out unreacted sulfur, as well as release trapped sulfur dioxide.
Useing a ballmill to throughly improve the contact area between reagents I guess would surpass all the difficulties in having a relatively neat desired compost.

[Edited on 8-11-2012 by Poppy]




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[*] posted on 7-9-2019 at 09:54


@markgollum said something in his post I didn't understand: "...the copper wire did mot melt so the peak temperature was certainly less then 184C."
Sadly it seems he's not around anymore to respond.

I really want to make Calcium Sulfide. It seems the easiest route is:

CaSO4 + 2C → CaS + 2CO2

Or am I wrong about this being the easiest path?
Prepchem website (http://www.prepchem.com/synthesis-of-calcium-sulfide/) describes this same reaction and tells me to use Plaster of Paris (CaSO4 • 1/2H2O).

My question is, would anhydrous Calcium Sulfate work better or worse, or not at all? Would Gypsum (CaSO₄·2H₂O) work too?

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[*] posted on 8-9-2019 at 00:17


Hi camurgo, plaster of paris looses its remaining water and becomes anhydrous well before the carbon starts to reduce the sulphate to sulphide so the answer to your question is Yes. If you are going to start with gypsum then I would dehydrate it first in the oven at about 200 C. The resulting crumbly mass is easily powdered. Good luck with the carbon reduction.
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[*] posted on 8-9-2019 at 00:24


Quote: Originally posted by camurgo  
@markgollum said something in his post I didn't understand: "...the copper wire did mot melt so the peak temperature was certainly less then 184C."
Sadly it seems he's not around anymore to respond.



Should be 1084C- the melting point of copper.
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[*] posted on 8-9-2019 at 06:46


Thank you @Boffis and @unionised !
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[*] posted on 8-9-2019 at 12:29


Per a source (see http://web.iiar.org/membersonly/PDF/CO/databook_ch2.pdf ), a simple low temperature path to a sulfide (and not a polysulfide), to quote:

"Sulfur vapor and ammonia react to give ammonium sulfide and nitrogen. Sulfur also reacts with liquid ammonia to produce nitrogen sulfide."

with the cited reaction in the case of liquid ammonia:

10 S + 4NH3 → 6H2S + N4S4

However, with sulfur vapors, a possible reaction with dry ammonia gas:

4 NH3 (g) + S (vapor) --> (NH4)2S (s) + N2 (g) + 2 H2S (g)

And, with excess NH3:

8 NH3 (g) + 3 S (vapor) --> 3 (NH4)2S (s) + N2 (g)

which is precisely as was claimed per the source above.

Now, dry ammonium sulfide is apparently unstable even at room temperature, liberating NH3 and H2S.

(NH4)2S (s) + Heat --> 2 NH3 (g) + H2S (g)

So, in the presence of a heated mix of dry CaCl2 and (NH4)2S, I would expect:

H2S (g) + CaCl2 (s) --> CaS + 2 HCl (g)

Note, the reaction is reversible (see https://en.wikipedia.org/wiki/Calcium_sulfide#targetText=Cal... ), so it is important to vent the HCl gas from the system. Note also:

NH3 (g) + HCl (g) --> NH4Cl (s)

NH3 (g) + CaCl2 (s) = CaCl2.NH3 (s)

[Edited on 8-9-2019 by AJKOER]
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[*] posted on 9-9-2019 at 19:30


Thanks @AJKOER!
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[*] posted on 10-9-2019 at 01:57


It seams there are several threads started with something but now all resulted in trying to make a calcium sulfide by a dry process. So, look at http://www.sciencemadness.org/talk/viewthread.php?tid=153772 and especially the comment by MrHomeScientist :

"

CaSO4 and aluminum is used as a heat booster in some thermite reactions (I did this for silicon thermite). That reaction produces calcium sulfide, which reacts with water to release copious amounts of H2S. So zinc would probably also work, if you can find powdered Zn.

"

This is definitely more affordable route than one with charcoal.


Also there are several active threads with discussion of other metal sulfides preparations. There are a lot of repeats indeed.

[Edited on 10-9-2019 by teodor]
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[*] posted on 11-9-2019 at 07:50


Thanks @teodor.
Couldn't find a local supplier that would sell aluminium powder to individuals. I can import it, but that would make it less affordable than charcoal.
Also, it seems it would be pretty hard to separate the products (which I believe are CaS and Al2O3).

Zn is easily available, but I can't find sources supporting that it could, as @MrHomeScientist seems to imply, react with CaSO4 somehow.
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