Indium sulfide

Hi. I made indium sulfide. I used indium metal nitric acid and sodium sulfide. It just has a nice color. It is not anhydrous. Anhydrous sulfide has a reddish-brown color.

Quote: Originally posted by vano

Gallium sulfide is also yellow. I have quite a lot of gallium, but it is difficult to make sulfide because it is hydrolyzed in water. You are right thallium sulfide is black, but I remember the crystals have a blue color. Most likely dark blue. [Edited on 23-1-2021 by vano] [Edited on 23-1-2021 by vano]

No problem

Vano your photo inspired me to also give this a go. Details below.

Indium nitrate solution:
First step was to get indium metal in solution, by reacting indium with nitric acid.
I expected the reaction to be:
2In + 6HNO3 = 2In(NO3)3 + 3H2
and accordingly 5.5g indium in 4 lumps was reacted with 11g 70% HNO3. The reaction started quickly with bubbling and release of brown NO2 fumes, see below.


After some time the reaction slowed down, and the beaker had to be heathed to speed it up. I also added another 6.5g 70% HNO3 as more acid was required when taking into account this reaction:
In + 4HNO3 = In(NO3)3 + NO + 2H2O
I left the reaction to slowly proceed, and went back every 3 or 4 hours to again heat the solution to near boiling and then let it cool slowly with the hotplate. The solution always went green to some extend which I first thought was due to impurities in the indium but I realised later the dissolved NOx caused the green color.
By the next morning all the indium was dissolved and I had a completely clear water colored solution of some 30ml. I then added water to increase the total volume to 150ml, and slowly boiled this down to around 30ml again. Purpose being to try and expell and acid or NOx that may still have been present. During the final phase of boiling there was no acid odor.

Next step was to bubble H2S through the indium nitrate. First step was to make iron sulphide. 42g iron filings was mixed with 28g sulphur and poured into a test tube:


The test tube was then heated in a bunsen burner. The reaction took quite a bit of heating to start; more then I remember from previous occasions. Maybe the iron filings was old and covered with oxidation? Anyway the expected red glow eventually started:


Once cool, the test tube was broken and a lump of 63g was recovered.


This was very hard but brittle, and was broken into smalled lumps using a hammer and chisel. Some 10g of FeS was placed in an erlenmeyer flask. Approximately 30ml hydrochloric acid (pool acid, around 320g/L) was diluted with an equal amount of water and added to the flask. Prior to this the solution of indium nitrate was placed in a large testube and some water added. I had never reacted H2S in solution before, and thought the longer time the bubbles will remain in the solution the better - thus using a tall test tube with a bit of water added. The simple setup is shown below:



The diluted HCl was added to the flask and the stopper applied. Bubbles was observed in the indium nitrate solution at some 1-2 bubbles per second. Intially nothing seemed to happen; probably it took some time to displace the air in the flask. Then a yellow suspension started to appear. Although some portion of the bubbles reached the surface there was no strong H2S smell at the test tube; probably some hydrogen was generated with the H2S? After 45 minutes there was thick yellow suspension and then the smell of H2S exiting the test tube became noticeable. At this point I removed the tube from the test tube and at the same time dumped an excess of copper sulphate solution into the Erlenmeyer flask to neutralise any H2S as it was being generated. The test tube with yellow product:



I left the test tube overnight for the yellow ppt to settle. The next morning it was still yellow, but a few hours later it changed to orange!


It was filtered off (and rinsed in the filter) and dried in the sun (under a steel dish) for a few hours, recovery was 3.5g of dry orange powder. This was less than 50% of the theoretical, based on having started with 5.5g indium. Thus, there had to be a significant amount of indium nitrate left in the filtrate. Photo of first crop below:


4.5g of sodium sulphide Na2S was dissolved in 30ml water and added to the filtrate. This caused another crop of yellow ppt to form. This was filtered off, rinsed with water in the filter, and placed in the sun under a steel dish to dry. As it dried this second crop also became orange! The second crop was 4.1g:


The first crop eventually became as orange as the 2nd crop. Total recovery was this 7.6g, close to the theoretical yield. But why was the reaction in aquas solution in the test tube so inefficient? Was the 45 minutes simply too short? Was the indium nitrate solution too dilute, or perhaps too concentrated? Should I have bubbled the H2S into a beaker with magnetic stirring to get better 'contact'?

Atomistry mentions yellow and red as color for In2S3 depending on method of preparation; looks like to got somewhere inbetween with my orange?

Quote: Originally posted by Lion850

(snip) The first crop eventually became as orange as the 2nd crop. Total recovery was this 7.6g, close to the theoretical yield. But why was the reaction in aquas solution in the test tube so inefficient? Was the 45 minutes simply too short? Was the indium nitrate solution too dilute, or perhaps too concentrated? Should I have bubbled the H2S into a beaker with magnetic stirring to get better 'contact'? Atomistry mentions yellow and red as color for In2S3 depending on method of preparation; looks like to got somewhere inbetween with my orange?

Quote: Originally posted by Bedlasky

(snip) Vano: Only cations from 2B class (Sn2+;4+, As3+; 5+, Sb3+; 5+) form soluble thiosalts in aqueous solution. Also some anions form soluble thiosalts (molybdate, tungstate, rhenate, vanadate). HgS and CuS are partially soluble just in concentrated suflides/polysulfides. Freshly precipitated CdS is partially soluble in (NH4)2S. Other thiosalts are prepared in solid phase.