# Curious precipitate from substitution reaction

Two solutions were prepared. 'Solution A' being $\ce {Na2S4}$ prepared from aqueous $\ce {NaOH}$ and elemental sulfur, the mixture heated and additional sulfur added until sulfur remained as a precipitate. 'Solution B' being a solution of $\ce {FeSO4}$ and $\ce {Fe2(SO4)2}$ prepared from reacting steel wool with $\ce{H2SO4}$, adding steel wool until reaction ceased. The liquid portion drained off and collected for use. Solution A was added to Solution B via squeeze pipette in intervals allowing precipitate to settle between additions. This was continued until the net solution began to turn yellow from a rising conventration of $\ce{Na2S4}$. The solution was washed drained and the precipitate collected, however its character is not as expected from micro particulate $\ce{FeS2}$ but rather a black oily colloidal mass was the collected product. Did I somehow manage to acquire $\ce{Fe2S4}$?

• from WIKI :which decays at a temperature over 20°C into FeS and sulphur.[2] $\ce {Fe2S3 → 2 FeS + S↓}$ – Aaron Scott Aug 10 '15 at 21:21
• Seems I made Iron III sulfide, the sample has decayed during the day becoming stiff and grainy with a sizable rotten egg odor in the house despite the sample being in a closed container....... – Aaron Scott Aug 10 '15 at 21:23