Solubility of SbCl3

[budullewraagh]

the other day i was looking through my "lange's handbook of chemistry" and i stumbled upon a table that had many compounds and their solubilities in H2O at various temperatures. out of curiousity, i looked for the most soluble compounds. i found antimony trichloride and found that at 40 celcius, 1368g of it can dissolve in 100mL H2O. it said that at 72 celcius it is completely miscible.

 

does anybody here find it to be possible to continuously add SbCl3 to H2O and NEVER precipitate it? i'll throw around some figures:

 

121.760+3*35.45=228.119=1 mole SbCl3.

1368/228.119=5.996870055M=saturated solution of SbCl3 in 100mL H2O.

100/18=5.5555 (repeating).

there are more moles of SbCl3 than H2O at 40 celcius. therefore there are more molecules of SbCl3 than H2O at 40 celcius. the number of H2O molecules is only 92.64091942% of the number of SbCl3 molecules there are. the Sb+3 migrate towards the O end of H2O while 3 Cl- atoms migrate towards the H in H2O.

 

that makes sense, except the Sb+3 and Cl- are so close to one another when in this saturated aqueous solution that i don't see why they don't precipitate.

 

also i'd like to add that the above calculations are only for the 40 celcius reading; again, at 72 celcius SbCl3 is "completely miscible".

 

can anybody help me out?

[tani]

I have read about extremely high solubility of SbCl3 in water several times, but I am having a hard time preparing a 2 millimolar solution of SbCl3 in water! I have tried heating it to 80C, stirring at room temperature for several days and also played around with pH a little bit, but the stubborn powder just does not seem to go into the solution. What am I doing wrong? Can someone help me out?

[woelen]

SbCl3 cannot exist in water. It is hydrolysed and a basic chloride is precipitated, or even an oxychloride is precipitated:

 

SbCl3 + 2H2O ---> SbCl(OH)2 + 2H(+) + 2Cl(-)

 

SbCl(OH)2 ---> SbOCl + H2O

 

SbOCl is insoluble