michalJenco - 17-2-2019 at 10:25
I did a reaction of tin metal with 31% hydrochloric acid. I wanted to speed it up so I heated it to almost boiling. When I took it off the heat and
let it cool to room temperature, small white/transparent spiky crystals formed. I thought these were supposed to be tin hydroxide (is this correct?).
I isolated them, evaporated off almost all of the remaining hydrochloric acid and added a minimal amount of hot saturated NaOH solution. A brown,
rust-like compound formed. What could this be?
[Edited on 17-2-2019 by michalJenco]
fusso - 17-2-2019 at 11:59
Maybe SnO?
Tin(II) oxide (stannous oxide) is a compound with the formula SnO. It is composed of tin and oxygen where tin has the oxidation state of +2. There are
two forms, a stable blue-black form and a metastable red form.
AJKOER - 20-2-2019 at 07:15
Or, perhaps SnO2 plus an Fe impurity as per Atomistry on SnO2 (see http://tin.atomistry.com/stannic_oxide.html ):
"Stannic Oxide, SnO2, occurs in crystalline and amorphous forms. As regards its crystalline forms, it is trimorphous, existing in tetragonal,
hexagonal, and rhombic crystals. Native stannic oxide, cassiterite or tinstone, occurs in tetragonal crystals, which when quite pure are colourless
and transparent, but are generally yellow, green, brown, or black, from the presence of oxide of iron or other impurity."
Note, a comment on iron contamination and HCl at https://www.reddit.com/r/chemistry/comments/4figqz/contamina... :
"HCl technical grade ends up contaminated by metals, as the dissolved Fe(II) gradually oxidizes to Fe(III) it attains yellow color"
[Edited on 20-2-2019 by AJKOER]