RU_KLO - 26-10-2023 at 11:53
Hi,
I need to make some soluble antimony salts (for using them then as samples to detect antimony)
better if I can get a Sb(III) and a Sb(V) salts.
I prefer as pure as I can possible get, in the sense Acid + Sb and not double displacement or any other element in there. (I had this problem with
cobalt: CoSO4 to carbonate to chloride. The chloride was contaminated with sulfates - tested with BaCl2. I know that no proper
cristallization/purification was performed between steps)
I have elemental Antimony.
After some research, it seems that Antimony is acid resitant. Antimony halides are quite toxic and I dont want to mess with Chlorine. (and dont have
concentrated HCl. Also the salts hydrolizes with water.
After reading antimony.pdf from SM library, candidate is:
Antimony Sulphate. (page 28) - -This is obtained by dissolving the metal or the oxide in concentrated sulphuric acid. On cooling, the sulphate
crystallises out in long needles. And it is very hygroscopic (Schultz-Sellack, Metzl). When water is added to it, the hydrate, Sb2(SO4)3 * 2 1/2H2O,
is formed. When heated in air, it changes to the trioxide and the tetroxide, with the evolution of SO3.
The neutral salt = (SO4)3Sb2 (Dexter, Adie).
from wiki:
2 Sb (s) + 6 H2SO4 → Sb2(SO4)3 + 3SO2 + 6 H2O.
this means that I should perform this outside.... and very dangerous (hot concentrated H2SO4 - SO2 generation)
How do you filter concentrated sulfuric acid? (Glass funnel with glass ball-marble? - do not know how is said in english, in spanish is "bolita" or
"canica"?) I dont have fritted glass filter.
I did not find any other, (nitrate requires fuming nitric acid which I do not have...)
Any other sugestion?
sub-question: "When heated in air, it changes to the trioxide and the tetroxide, with the evolution of SO3"
Could these mean than one can make oleum with antimony and concentrated sulfuric acid?
Sb + H2SO4 = Sb2(SO4)3. HEATING IN AIR: SO3 + oxide. then repeat oxide + H2SO4 = Sb2(SO4)3
Thanks
Bedlasky - 26-10-2023 at 15:58
Potassium antimony tartrate is probably your best option. It is soluble in water, not hygroscopic, easy to synthesise.
Dissolving antimony in conc. sulfuric acid will be most likely tedious and require heating. If you can get hands on conc. sulfuric acid, you can
surely buy conc. HCl and dilute H2O2 in a drugstore. HCl+H2O2 dissolve antimony just with moderate heating (do it outside or in a fumehood, because
HCl+H2O2 produce chlorine gas). You can then precipitate Sb(OH)3 with ammonia or sodium hydroxide and redissolve it in tartaric acid.
As for your CoCl2 - if you want to make very pure reagent it's better to:
1. Add slowly dilute carbonate into hot dilute CoSO4 solution with good stirring (this prevent inclusion of sulfate/alkali metal ions).
2. Heat precipitate on water bath for and half and hour to make it more crystalline (this also remove some impurities and make it easier to filter).
3. Wash preciptiate with hot water.
4. Dissolve precipitate in HCl and reprecipitate carbonate
5. Dissolve in HCl and if needed recrystallize
6. For precipitating in general is better to use some volatile salts - like ammonium salts, nitrates, ammonia etc. They can be easily drive off by
heating.
This should give you very pure stuff, but it depends how much pure you need it, you can skip reprecipitation and recrystallization if you don't need
it super pure.
j_sum1 - 26-10-2023 at 19:11
As an aside, potassium antimony tartrate is worth making if only because of the beautiful planar equilateral triangle crystals you get. Do the
crystallisation slowly or get a microscope