Description of experiment
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Needed compounds:
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hydrochloric acid : HCl
sodium chloride : NaCl
potassium iodide : KI
nitric acid : HNO3
basic bismuth nitrate : BiO(OH).4BiNO3(OH)2
Class:
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elem=Bi,I,Cl
coordination
Summary:
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Bismuth (III) forms a deep-orange iodo-complex and a yellow iodo-chloro
complex.
Description:
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Sequence 1:
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Dissolve some basic bismuth nitrate in dilute nitric acid, such that a clear
and colorless liquid is obtained. Add a small amount of a solution of
potassium iodide to this: At the places, where there is a large excess
amount of iodide, the liquid becomes deep orange. On shaking of the liquid
all deep orange liquid disappears and a black precipitate is formed. In
total there was an excess of bismuth (III) and hence, any local excess
iodide, which forms an orange complex [BiI4]-, is used up for formation
of black solid BiI3.
Add some sodium chloride to the solution: The sodium chloride dissolves
and the liquid becomes clear again. All of the black precipitate dissolves
and now a yellow complex is formed. So, bismuth is capable of forming a
chloro-iodo complex.
Sequence 2:
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Dissolve some basic bismuth nitrate in dilute hydrochloric acid, such that
a clear and colorless liquid is obtained. Add a small amount of a solution
of potassium iodide to this liquid: At the places, where the iodide is
in excess, the liquid becomes orange and clear. On shaking of the liquid,
the liquid remains clear and it becomes yellow. Now, a chloro-iode complex
of bismuth is formed immediately.