Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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acetone : CH3 CO CH3
bleach : NaClO
sodium thiosulfate : Na2S2O3 . 5H2O
sodium thiocyanate : NaSCN
ammonium thiocyanate : NH4SCN
urea : NH2 CO NH2
ascorbic acid : C6H8O6
chrome alum : KCr(SO4)2 . 12H2O
p-aminophenol HCl : NH2 C6H4 OH . HCl
sodium metabisulfite : Na2S2O5
catechol : C6H4 (OH)2
pyrogallol : C6H3 (OH)3
hydroquinone : HO C6H4 OH
sodium sulfide : Na2S . 3H2O
sodium sulfite : Na2SO3
sodium dithionite : Na2S2O4 . 2H2O
potassium iodide : KI
nitric acid : HNO3
Class:
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elem=N
redox
Summary:
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A large set of compounds is checked on interaction with concentrated
nitric acid. Many reductors react violently with nitric acid.
Description:
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A set of compounds is added to nitric acid. For each compound a fresh sample
of concentrated nitric acid (between 60% and 68% by weight) is taken and a
little quantity of the compound is added to the acid in pure form. Below, the
result is given for each of the tested compounds.
All experiments were carried out at room temperature. Liquids were not
heated in these experiments.
sodium dithionite: For appr. 2 seconds no clear reaction, but suddenly a
very vigorous reaction starts. Lots of NO2 are produced.
The liquid becomes a little turbid, probably due to
formation of finely divided sulfur.
sodium thiosulfate: The crystals are covered by a thin yellow layer (this
layer probably consists of sulfur). On shaking this
thin layer disappears again and the crystals dissolve.
The liquid becomes clear and colorless.
Approximately 30 seconds later, suddenly a fairly large
amount of NO2 is formed, the liquid turns blue/green
and a little turbid. The liquid becomes warm.
bleach: Formation of chlorine, which can be seen as a pale green gas above
the liquid. The liquid becomes yellow/green. A strong smell of
elementary chlorine can be observed.
acetone: Both liquids mix, no visible reaction (at least not within a few
minutes).
pyrogallol: The solid partly dissolves. It does dissolve, but not as easily
as in water. The liquid becomes pale pink/brown. No gas is evolved,
no other visible reactions, no heat is produced.
hydroquinone: Slow evolution of a gas or a gas mixture. The air above the
liquid becomes brown, so the gas probably is NO, NO2 or a
mixture of them. The liquid turns yellow. The needle-like
crystals of hydroquinone turn dark green, they discolor from
white to dark green within a few seconds after contact with
the acid.
catechol: Extremely violent reaction, thick clouds of NO2 are produced and
the liquid becomes very hot (boiling??). The violent reaction
holds on for appr. 15 seconds and then it suddenly stops (probably,
due to exhaustion of the catechol). The liquid becomes red/brown.
Its color is about the same as the color of the gas mixture above
the liquid.
sodium metabisulfite: A vigorous reaction occurs, formation of NO/NO2, the
solid quickly dissolves while evolving a lot of gas.
sodium sulfite: A vigorous reaction occurs, formation of NO/NO2, the
solid quickly dissolves while evolving a lot of gas.
p-aminophenol HCl: No visible evolution of gas. The liquid becomes yellow.
Crystals, not covered by liquid, but affected by HNO3
vapor, become purple.
On dilution with water to appr. four times the original
volume, the liquid quickly turns dark reddish purple.
Probably the characteristic indigo/purple compound is
formed on oxidation of p-aminophenol, but the mix with
the yellow compound may make this appear more reddish.
chrome alum: No reaction, the solid partly dissolves, the liquid becomes
violet. No formation of chromate/dichromate.
ascorbic acid: Slow evolution of a gas, air above liquid turns brown. All
solid dissolves. The liquid remains colorless.
urea: No visible reaction, at least not within a few minutes.
ammonium thiocyanate: The solid dissolves, the liquid turns pink. No evolution
of a gas.
On dilution with water the pink color disappears and
the liquid becomes colorless again.
sodium thiocyanate: The solid dissolves, the liquid turns pink/brown. No
evolution of a gas.
On little dilution with water the color of the liquid
becomes less intensive and more yellowish. On stronger
dilution the liquid becomes colorless.
sodium sulfide: Very vigorous reaction, the liquid becomes turbid, formation
of a gas and smoke. The smoke might be due to reaction of
liberated H2S with NO and/or NO2, with the formation of free
sulfur, which appears as smoke.
potassium iodide: The solid immediately is covered by a black layer of iodine.
Gas is evolved and the air above the liquid becomes pale
brown.