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Author: Subject: Calcium Sulphide
FGP
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Calcium Sulphide

Archives show that calcium sulphide was produced by heating sulphur and oyster shells (presumably in powder form). The latter were regarded as a pure source of calcium carbonate. Can someone on this forum suggest the ideal reaction conditions in order to obtain calcium sulphide from these materials? Please accept old fashioned UK spelling of sulphur and sulphide.
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chemoleo
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Lol, I also prefer Sulphide & sulphate - it's respect for the ancient chemists!

Anyway, altough I haven't checked, I would think you would get the reaction going by mixing stoichiometric amounts, and heating/melting until the evolution of SO2 (sulphur dioxide) stops.
SO2 should evolve if the reaction works according to (which is very likely):

1. CaCO3 + S --> CaS + CO2 + 1/2 O2
2. S + O2 --> SO2

Altogether:

2 CaCO3 + 3S --> 2 CaS + 2 CO2 + SO2

SO2 is one of the products, which is detectable by smell (toxic). The oxidation of sulphur should partially drive the reaction.

Homework question?

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Calcium sulphide is phosphorescent (glow-in-the-dark), so it could be a really nice thing to be done.
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Really? Simple as that? No dopants or anything? Sounds too good...

Any first hand experience?
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 Quote: Originally posted by a_bab Calcium sulphide is phosphorescent (glow-in-the-dark), so it could be a really nice thing to be done.

Only when doped with zinc sulphide.

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unionised
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Classic synthesis is gypsum and coke.
Just hope that the gypsum you use has the right imputities to dope the sulphide.
A similar trick is still used for getting barium salts from the ore. The sulphate is insoluble and almost inert; reduction to the sulphide gives a product that disolves in acid.
chemoleo
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But what if you want to recycle BaSO4, back into soluble salts? Always wanted to find an easy way to do this, without massive heat etc...

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Actually, you can use as a doppant Bi or other metals. The tricky part is to create the crystalin structure properly and this is achieved at high temps, and long times.
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 Quote: Originally posted by chemoleo Lol, I also prefer Sulphide & sulphate - it's respect for the ancient chemists! Anyway, altough I haven't checked, I would think you would get the reaction going by mixing stoichiometric amounts, and heating/melting until the evolution of SO2 (sulphur dioxide) stops. SO2 should evolve if the reaction works according to (which is very likely): 1. CaCO3 + S --> CaS + CO2 + 1/2 O2 2. S + O2 --> SO2 Altogether: 2 CaCO3 + 3S --> 2 CaS + 2 CO2 + SO2 SO2 is one of the products, which is detectable by smell (toxic). The oxidation of sulphur should partially drive the reaction. Homework question?

Dear Chemoleo,
You've pointed to what I think I was asking - surly heating the mixture in air will favour your reaction '2'?

"2. S + O2 --> SO2" and so ending up with little or no calcium sulphide.?
Not a homework question - I am one of the ancients transcribing an early chemistry essay.
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If you heat up CaCO3 and sulphur, the products should be CaS, SO2 and CO2 (equation 3, after 'Altogether'. True, you lose 1/3 of the sulphur into the formation of SO2, but the remaining 2/3 goes into the formation of 2CaS.
You can heat the reaction in a vacuum if you wish, and it would still work. The oxygen that is needed for equation 2 to form SO2 is derived from the product of reaction 1. Outside air might interfere, if the reaction gets hot enough for the sulphur to selfignite. I doubt you will need temperatures like that though. Even then, if the reaction mix exposure to air is minimal, with no further access to it (i.e. in a closed container, with a pressure valve), then you should have no problem with the air interfering... sulphur losses will be minimal. Just use a very slight excess then, and all will be good

[Edited on 19-12-2003 by chemoleo]

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chemoleo: To get soluble Ba2+ from BaSO4, you just have to boil it with concentrated sodiumcarbonate solution approx. 15 min and then boil off the water until nearly dry. Then put in some more water, stir and let it settle. Decant it and repeat two more times. The Bariumsulfate will have turned into Bariumcarbonate now, so just rinse it and dissolve it with your acid of choice. This works with calciumsulfate and strontiumsulfate as well.
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I bet this calcium sulfide production takes very high temperatures. I'm pretty sure I remember trying it years ago with a torch and not having any luck. There is a similar reaction to make calcium carbide using CaO and C. I definitely remember trying this one several times heating the mixture with a torch for long periods of time and never having a bit of success.

If someone does manage to make either calcium sulfide or calcium carbide using nothing hotter than a torch I'd be interested in hearing how they did it.

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I found this recipe for a phosphorecent compound in an old italian book, I translated the best I could (my native language is neither italian nor english), and I added the original text in case someone better qualified wants to help:

mix 20g “calce caustica” (I think that’s calcium oxide) with 5g powdered sulfur and 2g starch. Wet this mix with 8ml of a solution made of 0,5g of bismuth’s “sottonitrato”(help needed here) in 100ml alcohol (previous addition of HCl)(?). When alcohol is dry, heat the mix in a closed crucible to bright red for 20 minutes. After it cools, cut the thin superficial layer of “gesso” (plaster?!), pulverize the fused mass and heat it again for 15 min at the same temp.

I made some crude attempts to produce phosphorecence using calcium carbonate, sulfur and a tiny bit of zinc powder. They all failed miserably. Not a hint of light. Awful lot of stench.

Original text:
“Gr. 20 di calce caustica si mescolano com gr. 5 di solfo in polvere e gr. 2 d’amido. Si umeta a goccie questa miscela com 8 cc di d’uma soluz. Di gr 0,5 de sottonitrato de bismuto in 100 cc d’alcool (previa addizione d’ac clorídrico) in modo a ottenere un’intima suddivisionde del bismuto. Quando l’alcool è svaporato all’aria, si scalda il miscuglio, in crogiuolo coperto per circa 20 minuti al rosso chiaro, e dopo reaffreddamento, si toglie il sottile superficiale strato di gesso, si polveriza la massa fusa e si scalda ancora per un quarto d’ora alla temp. di prima.” – Ricettario Industriale – I. Ghersi – Ulrico Hoepli Ed. 1915
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Calce caustica is probably calcium Hydroxide. You know, caustic soda=NaOH so maybe Calce Caustica=Calcium Hydroxide. Bismuth's Sottonitrato would be bismuth nitrate or nitride maybe?

I don't speak a whole lot of italian so don't take what I suggested as neccesarily true. Perhaps you should try to U2U or wait for Nevermore. His/her prifile says he/she is from Italy. I don't know if that means they speak italian, but I'd say the chances are higher than someone from elsewhere in the world.
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CaC2 and CaS

Hodges, for the production of CaC2 you need VERY high temperatures. I think it is made under an electric arc. In fact, some time back i managed to get hold of a very good transformer (5 kW), at 42 Volts. With this one, I fused out the power in our house a number of times, possibly because I used more than 5 kW . Anyway, this way I actually MADE about 4 grams of CaC2, with CaO and carbon. When I put some of those chunks into water, they evolved bubbles, that violently burned with a smoky yellow flame once ignited .
I believe the high temperature is required (>>2500 K) for the formation of the triple bond, in part. Thought this is a guess.
Anyway, that clearly explains why you can forget making CaC2 with a blowtorch.

Anyway, that's why I dont think the CaCO3/S thing would require AS MUCH temperature as with the CaC2 production. Sure, it is possible you need higher temperatures than those you can achieve with a blow torch. But I dont know the temperature that is required. Sorry

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secret ingredients

Trying to decipher old recipes? Could the sottonitrato de bismuto be Bismuth Subnitrate? I've always has a facination for glow in the dark phosphorescent materials too. But no success. If Bismuth is needed as a trace element to dope the Calcium Sulfide, perhaps a little Pepto Bismol , or a generic replacement, would work, as it contains bismuth subsalicylate as its active ingredient. Each 15 ml contains 262 mg of the stuff. Most of the other inert ingredients are organics that would burn off and a little magnesium aluminum silicate.
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 Quote: Originally posted by chemoleo Anyway, that's why I dont think the CaCO3/S thing would require AS MUCH temperature as with the CaC2 production. Sure, it is possible you need higher temperatures than those you can achieve with a blow torch. But I dont know the temperature that is required. Sorry

If I were to try this, I'd grind up a powder consisting of CaCO3 and a large excess of Sulfur. I'd pack it into a crucible with a loose fitting lid (to exclude O2 as much as possible) and cook the bejeebers out of it in a small electric kiln or with a high temperature torch.

I don't know if it would work, but the old pioneer chemists were big on crucibles and cooking the bejeebers out of things, so I bet I'm on the right track...
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I have this vague memory that the boiling point of sulphur (444.6C) was used as a calibration point for fairly high temperature thermometry. Can anyone imagine why I might mention this fact in this thread?
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Lol, see, that's why I thought this reaction wouldnt require THAT much heat
However, from the very first post it is not clear whether the reaction was done in a pressurised system (to contain boiling sulphur). Yet, as gases are evolved in due course of the reaction, the pressure would increase, possibly driving the reaction backward to a greater and greater extent (equilibrium).
Anyway, this pressurisation sounds unlikely from this. so yes, it's very likely that the temperatures required for the reaction are below the boiling point of sulphur. good point.

[Edited on 20-12-2003 by chemoleo]

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wouldn't excess S lead to formation of polysulfides?
hmm... if "I" were to try CaS, I would make some Al-plaster comp which will be lots of fun AND as a result it'll give me some CaS in its ash (mixed with aluminum oxide). isolation of CaS seems the hardest step. I would say add the ash in icecold water (do it outside!) let the filtrate evaporate while not letting the sol warm up (cold days)
the problem is that CaS is slightly soluble in water so huge amounts of water is needed which will take a long time to evap specially @ cold temps. I read CaS partly decomposes in water (to slaked lime and hydrogen sulfide) I think it means decomposition continues till it reaches a PH in which the equilibrium stablizes
anyway if it is used as a source of hydrogen sulfide the seperation maybe unnecessary (dependes on what you want it for)

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Gr. 20 di calce caustica si mescolano com gr. 5 di solfo in polvere e gr. 2 d’amido. Si umeta a goccie questa miscela com 8 cc di d’uma soluz. Di gr 0,5 de sottonitrato de bismuto in 100 cc d’alcool (previa addizione d’ac clorídrico) in modo a ottenere un’intima suddivisionde del bismuto. Quando l’alcool è svaporato all’aria, si scalda il miscuglio, in crogiuolo coperto per circa 20 minuti al rosso chiaro, e dopo reaffreddamento, si toglie il sottile superficiale strato di gesso, si polveriza la massa fusa e si scalda ancora per un quarto d’ora alla temp. di prima.” – Ricettario Industriale – I. Ghersi – Ulrico Hoepli Ed. 1915

translation (where did you get this thing, looks like an hystory book is the oldest italian i've ever seen, rather hard to translate)

mix 30 grams of CaO with 5 grams of powdered S and 2 grams of starch.,This is wetted with 8cc of a solution of Bismuth-NO2 in 100cc of ethanol (adding some HCL in order to obtain a fine mixing of the bismuth). When the ethanol has evaporated warm the mixture in a closed vessel till red for 20 mins, after that cool it, toss the thin layer of gypsum on top, powderize the mass and repeat the process (heating) for 15 mins.

Note, i suppose "calce caustica" is CaO being it caustic, it can be reasonable to be Ca(OH)2 (as with NaOH "soda caustica" but i suppose the name caustic is given only to the ones that burn the skin, i don't think it should be CaCO3 or should have been called just "calce or calcina"

[Edited on 30/12/2003 by Nevermore]

Nevermore!
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Thank you Nevermore.
It's a book that belonged to my grandfather, published in 1915.

As unionised pointed out, the boiling point of sulfur is 444.6C. I can't see how you can bring the reactants "till red" without some pressure vessel.
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i don't know but i suppose the sulphur will react before reaching boiling temperature so overheating it will just burn out the excess sulphur to get a more clean product..

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Substitution of Calce caustica

 Quote: Originally posted by Tacho I found this recipe for a phosphorecent compound in an old italian book, I translated the best I could (my native language is neither italian nor english), and I added the original text in case someone better qualified wants to help: mix 20g “calce caustica” (I think that’s calcium oxide) with 5g powdered sulfur and 2g starch. Wet this mix with 8ml of a solution made of 0,5g of bismuth’s “sottonitrato”(help needed here) in 100ml alcohol (previous addition of HCl)(?). When alcohol is dry, heat the mix in a closed crucible to bright red for 20 minutes. After it cools, cut the thin superficial layer of “gesso” (plaster?!), pulverize the fused mass and heat it again for 15 min at the same temp. I made some crude attempts to produce phosphorecence using calcium carbonate, sulfur and a tiny bit of zinc powder. They all failed miserably. Not a hint of light. Awful lot of stench. You could try to use calcium carbide in place of the calcium oxide.The reasoning behind this theory is that Calcium Carbide reacts with water to create Carbon Hydride.

.....
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It shouldn't be sulfur + CaCO3, sulfur wouldn't reduce carbon easily. Carbon WILL reduce CaSO4,with CaS forming at 1000 C and SO2 forming at 1500 C.
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