Aluminuim sulfide synthesis

Today I performed my first "ok" thermite to make Aluminium sulfide.

Aluminium is handfiled (from a processor heatsink)
Sulfur is mortar crushed from sulfur cyllinders.
Boths powders are mixed in the mortar.

First try was to make a loose "mountain" with a sparkle inside,
Sulfur melted (and got ignited "blue fire") but no thermite.

Second try was to put the mixture (aprox 1gr Al + 1,5gr S) in a 8ml testube - was compacted and added a sparkled with preassure in the middle.
Ignited the sparkler, but it did not ignite the thermite. A hole long as the sparkled - with molten sulfur - was made.

third try, in the hole, another sparkler was inserted + some magnesium ribbon. It ignited, some sparks flyed, the test tube got red and deformed.

Once everything was cold, the test tube was crushed and H2S smell was evident.

A small globe of aluminium is seen, covered with (I think) is Al2S3.

Pic attached.(the black part is test tube glass)

From seeing the globule of Aluminium, it seems it all not reacted. Probably because in the second try, the sparkler removed some Sulfur.

Which is the best by weight ratio between sulfur and Aluminium? (example 2:1 (sulfur/Aluminium)

Any suggestions on making this thermite? (better ignition sources?) Maybe direct blowtorch fire? - Sulfur melted quite rapidly.

Quote: Originally posted by fx-991ex

I did the same thing a few months ago, i tried with Al blended in mineral oil(removed mineral oil of course) and it didnt work. But, i did it again with Al sanded from a Al block and it ignited using a red hot Stainless-steel metal piece. Yes, it is best to ignite the mixture with a gas flame or a red-hot stainless steel rod, as magnesium in particular, or possibly a sparkler, will contaminate the resulting mixture. If you don't sublimate the Al2S3 from the mixture it will be of poor quality, but it depends on what you want to use it for afterwards.

Quote: Originally posted by RU_KLO

Thanks, regretfully 1500ºC sublimation is out of my reach....

For interest: In the 1930s, the well-known German chemist Hermann Rompp considered the possibility of synthesizing Al2S3 from Al powder and thiosulfate. With that said, there is one sulfur atom in the thiosulfate that is relatively loosely chemically bonded and this sulfur atom will form bright yellow Al2S3 with the aluminum. In practice, it would probably be difficult to separate it from the resulting reaction mixture, perhaps it could somehow be done based on the different melting temperatures of the reaction products. If ammonium thiosulphate were used, perhaps the other components formed by the chemical reaction could be evaporated by violent annealing. I state this rather for interest and consideration



[Edited on 20-3-2024 by Admagistr]

Quote: Originally posted by Admagistr

I recall that there used to be a method of melting PbS with powdered aluminum in a crucible to prepare Al2S3. It separated the lead, which was cast off, leaving Al2S3 of perhaps decent purity.

Quote: Originally posted by RU_KLO

thanks, regarding this procedure, how to easily obtain PbS? Could I melt Pb with Na2CO3 + S? (like polisulfide preparation)? or adding a soluble lead salt (lead acetate comes into my mind) in a polisulfide solution (made from Na2CO3 + S) (I would like not to work with H2S gas bubbling) and regarding furnace (which I dont have) temperature, could I use a camping stove (outside) and a tin can (food can)? I have made fishing weight this way. Or temperatures should be 500°C +?

You can get PbS by heating lead with sulfur, your camping stove will do for that, or from an aqueous solution by mixing lead acetate with an alkaline sulfide, like sodium sulfide. Na2S is cheap and quite available.You can also use a solution of thiourea and lead acetate, after several chemical intermediate reactions and after heating the reaction mixture you get lead sulfide and even crystalline synthetic galena by this method. For the synthesis of PbS+Al, a Mecker torch would be best. A temperature of over 500 C would be needed, preferably 1100 C, but the reaction is exothermic, so just heat the mixture to that temperature not too long. You can put a crucible on the burning charcoal and blow a stream of air into charcoal, that should do the trick

The crucible can be cheap chamotte, clay, or expensive corundum, I would not use it because it might be a problem to clean it afterwards.The steel can is perhaps disposable, but the chamotte would be better because of possible Al2S3 contamination from the used can
Just a quick note. Just lead and sulfur, you don't need Na2CO3 for that.

[Edited on 21-3-2024 by Admagistr]