Experiments for 'Cr'
Below follows a summary of all experiments, matching your search. Click one of the EXPERIMENT hyperlinks for a complete description of the experiment.
Results for 'Cr':
EXPERIMENT 1
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Potassium dichromate is sparingly soluble in thionyl chloride, giving an
intensely colored red/orange/brown solution, which on addition to water
at once becomes green with a blue hue.
Potassium chromate does not dissolve in thionyl chloride. The solid changes
color from yellow to yellow/orange, and the solution becomes slightly colored,
but this faint reaction may be due to minor impurities in the potassium
chromate or thionyl chloride. If any potassium chromate dissolves, then it
is a very small amount.
EXPERIMENT 2
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Thionyl chloride is not soluble in concentrated sulphuric acid, or only
sparingly soluble.
The mix of thionyl chloride and sulphuric acid is capable of forming chromyl
chloride from potassium dichromate.
EXPERIMENT 3
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Benzotriazole is not oxidized by air. Apparently it forms a coordination
complex with chromium (III).
EXPERIMENT 4
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Tannine (a polyphenolic compound of large molecular weight of indeterminate
composition) reacts with many metal ions, forming highly coloured complexes.
It also shows some other reactions. The exact type of reactions is not
always clear.
The tannine, used in these experiments, was brown. It's intended use is
as an additive for making wine.
EXPERIMENT 5
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Chromium (III) has many different colors, depending on coordinated ligands.
EXPERIMENT 6
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Chromium (III) has many different colors, depending on coordinated ligands.
EXPERIMENT 7
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Cr (III) reacts with the hexacyanoferrate (II) and hexacyanoferrate (III).
EXPERIMENT 8
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Chromium (III) can be converted to chromium (VI) in strongly alkaline
environments.
EXPERIMENT 9
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Oxidation of chromium (III) to chromium (VI).
EXPERIMENT 10
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When Cr3+ is added to an aqueous solution of ammonia, then a precipitate
is created, which does not dissolve on addition of much more ammonia.
EXPERIMENT 11
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Cr(III) can be reduced to Cr(II) by a zinc nail. On reoxidation to Cr(III)
a coordination complex appears to be created, both with sulfate and with
chloride.
EXPERIMENT 12
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Chromium (III) can have many different colors, depending on how it is
created and with which it coordinates.
EXPERIMENT 13
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Chromium (III) can be oxidized to chromium (VI) by persulfate in alkaline
environments.
EXPERIMENT 14
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Chromium (III) does not quickly build a coordination complex with ammonia,
such as is the case with copper (II) and nickel (II). Even in a slightly
alkaline environment of dilute ammonia, chromium (III) can be oxidized to
chromium (VI) by the action of hydrogen peroxide. Reduction, back to
chromium (III) is not easily accomplished in alkaline environment.
EXPERIMENT 15
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The color of chromium (III) depends on how it is part of coordination
complexes.
EXPERIMENT 16
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Potassium dichromate dissolves very well in hot water. In the cold nice
crystals separate out of the solution.
EXPERIMENT 17
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Silver (I) gives a bordeaux-red precipitate with dichromate, which
slightly dissolves in water.
EXPERIMENT 18
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Bleach is capable of oxidizing chromium (III) to its hexavalent state, but
this is not accomplished easily and completely.
EXPERIMENT 19
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EDTA builds pink complexes with chromium (III). This complex is destroyed
in strongly alkaline environments.
EXPERIMENT 20
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Chromium (III) is oxidized to dichromate (chrome (VI)) by persulfate. This
reaction is catalyzed by silver (I).
EXPERIMENT 21
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Basic chromium (VI), chromate, is not capable of oxidizing ascorbate. On
acidification, immediate oxidation occurs and a coordination complex is
formed.
EXPERIMENT 22
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When chromium (III) is created by reduction from dichromate with acidified
sulfite, then a green ion is formed. When acidified sulfite is added to
violet chromium (III), then the ions remain violet.
Apparently the way of creating chromium (III) determines its color (and
hence to what it is coordinated).
EXPERIMENT 23
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When chromium (III) is created from dichromate, its color depends on the
reductor used and on the acid which is used for supporting the redox
reaction.
EXPERIMENT 24
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Chromate is reduced by dithionite in strongly alkaline solution, but this
reaction proceeds slowly.
EXPERIMENT 25
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Chromium (III) builds a green coordination complex with metabisulfite,
not with thiosulfate.
When hydrogen peroxide is added, then the complex with metabisulfite is
destroyed.
EXPERIMENT 26
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Sodium dichromate dissolves in water very well, much better than potassium
dichromate. When it is reduced, then it is hard to crystallize a chrome
(III) salt or a mixed sodium chrome (III) salt.
EXPERIMENT 27
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Chromium (III) apparently builds a coordination complex with hydroxyl amine,
but this complex does not simply form from chromium (III) salts and
hydroxyl amine. If chromium (III) is formed by means of reduction of
chromium (VI) in the presence of hydroxyl amine, then the complex is
formed. If hydroxyl amine is added to chromium (III) without redox reaction,
then another complex is created.
EXPERIMENT 28
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Potassium tetraperoxochromate slowly dissolves in concentrated sulphuric
acid, it quickly dissolves (and decomposes) in dilute acid.
EXPERIMENT 29
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Hexavalent chrome forms a stable volatile compound, when mixed with chloride
in strongly dehydrating conditions. The compound formed is called chromyl
chloride and its constitution is CrO2Cl2.
EXPERIMENT 30
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From ice cold strongly alkaline solutions of potassium chromate, one can
create peroxochromate by adding hydrogen peroxide carefully.
EXPERIMENT 31
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Tetraperoxochromate does not dissolve well in water and is not stable.
In acidic environments it cannot exist at all. It decomposes, yielding a
large amount of oxygen. It is not capable of oxidizing hydrochloric acid
to chlorine, it simply decomposes, giving off all its oxidizing power
in the form of oxygen.
EXPERIMENT 32
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When potassium dichromate is reduced by thiourea in acidic environments, then
a moss-green compound of chromium (III) is formed. When already existing
chrome (III) is added to a solution with thiourea, then the moss-green
compound is not formed.
EXPERIMENT 33
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Chromium (III) builds a coordination complex with nitrite of a fairly
intense purple color.
EXPERIMENT 34
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Chromium (III) builds a purple complex with EDTA, both when it is created
from dichromate and when it already exists and is brought in contact with
EDTA. When the pH is too low (or is this due to formation of a complex with
sulfate?), the formation of the complex does not occur.
EXPERIMENT 35
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Chromium (III) gives coordination complexes of all kinds of colours, when
formed from a redox reaction, starting with dichromate.
EXPERIMENT 36
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Bisulfite and sulfite form coordination complexes with chromium (III). The
exact behaviour strongly depends on the pH of the solution.
When the pH is raised with sulfite and then decreased again with sulphuric
acid, then the color does not revert to the original color of aqueous
chromium (III). Probably a new compound is found, which is inert and does
not fall apart quickly in acidic environments.
EXPERIMENT 37
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When dichromate is brought in contact with peroxide, then after an initial
transient, a green variation of chromium (III) is produced. This compound,
however, slowly changes to a bluish/violet compound.
EXPERIMENT 38
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When dichromate is reduced by means of adding hydrogen peroxide, then after
the initial transient a green compound is formed, even when the acid in
which the dichromate is dissolved is nitric acid (nitrate is supposed to
not form a coordination complex with chromium (III)). Is this green compound
a coordination complex with nitrate? or with hydrogen peroxide?
This coordination complex can easily be destroyed by heating.
EXPERIMENT 39
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Chromium (III) builds a coordination complex with sulfate in the heat.
This coordination compound does not crystallize well.
EXPERIMENT 40
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Chromium (III) forms a lavender precipitate, when combined with hydroxyl
amine in alkaline environments. This compound does not dissolve in
strongly alkaline environments.
EXPERIMENT 41
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Dichromates are not capable of oxidizing nitrite in neutral environments.
When some acid is added, then the oxidation proceeds, but a fairly low
pH is needed for a fast and complete reaction.
EXPERIMENT 42
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Chromium (III) cannot be oxidized to chromium (VI) by vanadium (V) species
or bromates in strongly alkaline environments. Peroxodisulfate is capable
of achieving this.
EXPERIMENT 43
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Dichromate is not capable of oxidizing formiate in reasonable time.
EXPERIMENT 44
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Dichromate is capable of oxidizing tartaric acid and a colorless gas is
formed in this reaction (probably CO2). The liquid becomes purple/grey
(hard to describe color, depending on viewing illuminant).
The reaction product does not form a special complex in alkaline environment,
the familiar green color of chromium (III) in alkaline environments is
created. Addition of glycerol does not result in formation of a special
coordination complex.
When, however, dichromate is reduced by an excess amount of glycerol, then
a special coordinate complex appears to be formed, when the solution is
made alkaline. Even addition of acid does not destroy this complex.
EXPERIMENT 45
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Chromium (III) builds a nice brightly colored green complex with phosphates.
This compound has no bluish hue, like sulfate gives with chromium (III).
Chloride also builds a complex. Formation of these complexes is not on
simple addition of a chromium (III) salt to the corresponding anions.
Heating is required.
EXPERIMENT 46
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Dichromate can be reduced by hydrochloric acid with some difficulty.
EXPERIMENT 47
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Dichromate reacts with hydrogen peroxide, also when no acid is present.
An initial compound is formed quickly, which decomposes slowly, releasing
heat. Due to heating up, the reaction proceeds faster and faster, until
all of the peroxide has been used up.
EXPERIMENT 48
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Chromic acid reacts with hydrogen peroxide under formation of a dark blue
compound. When more hydrogen peroxide is added, then apparently the pH of
the liquid becomes too high and other almost black compounds are formed,
which quickly decompose.
EXPERIMENT 49
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Dichromate reacts with hydrogen peroxide, yielding chromium (III) as the
final product, in acidic environments. In alkaline environments, chromium
(III) yields chromate with hydrogen peroxide.
EXPERIMENT 50
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Dichromate is reduced by sulfite in neutral/slightly alkaline enviromments.
Under these conditions a jelly-like precipitate is formed, which is fairly
stable and does not dissolve immediately in dilute sulphuric acid. This
jelly-like precipitate is a chromium (III) compound.
The compound, however, does dissolve easily in strongly alkaline liquids.
The formation of this compound is not affected by the type of the cation
in the chromium-compound.
EXPERIMENT 51
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Hydroxyl amine gives a brown coordination complex when it reduces hexavalent
chromium to trivalent chromium in alkaline environments. This coordination
complex is really due to the hydroxyl amine. When other reducing agents are
used in the presence of ammonia in alkaline environments, then no similar
reaction product can be obtained.
EXPERIMENT 52
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When dichromate is added to sulfide, then a transient highly coloured
compound is formed, immediately followed by reduction to green chromium (III)
in alkaline environment.
EXPERIMENT 53
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Chromium (III) forms a purple coordination complex with nitrite. This
complex has a fairly bright pink/purple color, which differs quite a lot
from the color of aqueous chromium (III).
EXPERIMENT 54
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Potassium dichromate dissolves in methanol, albeit not as well as in water.
Potassium chromate hardly dissolves in methanol. When ammonium thiocyanate
is added, then the liquid becomes deep yellow. Is this due to chromate, or
is this some reaction product from the thiocyanate?
EXPERIMENT 55
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Chromium (III) is not reduced to chromium (II) by borohydride. Alkaline
chromium (VI) is only reduced slowly by borohydrode. On acidification the
reduction goes at once, but no further than the +3 oxidation state.
EXPERIMENT 56
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Aniline, combined with acidified dichromate gives intensely colored compounds.
EXPERIMENT 57
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Aniline gives colored compounds with chromium. The colors are remarkably
intense.
EXPERIMENT 58
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Chromium (III) chloride initially gives a green solution in water, which on
standing turns violet/grey. The chromium/chloride complex slowly is changed to
plain aqueous chromium and free chloride ion. This takes a few days before
completion.
With nitrite ions, a purple complex is formed.
EXPERIMENT 59
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Chromium (III) chloride dissolves in DMSO to quite some extent. A precipitate
is formed slowly. Is this a DMSO complex?
EXPERIMENT 60
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Chromium (III) chloride hexahydrate cannot be dehydrated by simple heating.
Copper (II) chloride dihydrate can perfectly be made anhydrous.
EXPERIMENT 61
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Neodymium ions form a yellow/lime green precipitate with chromate ion.
The solubility of neodymium chromate is very low.
Neodymium dichromate is much more soluble, at least in acidic solution.
EXPERIMENT 62
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It is not possible to make methylammonium chromate or methylammonium
dichromate by mixing solutions of CrO3 and CH3NH2 in water and letting
the solution evaporate. Apparently, chromic acid is not sufficiently
acidic in aqueous solution to protonate the methylamine to a salt.
This is in strong contract with perchloric acid, which, when mixed
with excess methylamine, gives a nice dry solid CH3NH3ClO4 on evaporation.
This also is in strong contrast with ammonia, which gives a mix of
(NH4)2CrO4 and (NH4)2Cr2O7 when excess ammonia and CrO3 are mixed and
allowed to evaporate to dryness.
EXPERIMENT 63
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Dichromate is quickly reduced by tin (II) ions.
Hydrogen peroxide does not show a visible reaction with tin (II) ions.
EXPERIMENT 64
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Potassium dichromate reacts with formic acid, producing a gas (CO2) and
itself being reduced to trivalent chrome.
EXPERIMENT 65
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Lead (II) salts give a yellow precipitate of lead chromate with dichromates.
When this precipitate is made alkaline, then it turns orange.
EXPERIMENT 66
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Hexavalent chromium oxidizes ascorbic acid. This reaction is fast and even
proceeds without adding additional acid. The acidity of the ascorbic acid
suffices to make the reaction proceed quickly.
The resulting chromium(III) forms an intensely colored dull-green complex
(green/grey, almost black at moderate concentration).
EXPERIMENT 67
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Cesium alums seem to be nearly insoluble compounds.
EXPERIMENT 68
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Dichromate/chromic acid is reduced by malic acid and in this reaction an
intensely colored purple complex of chromium(III) is formed. If the reaction is
performed in the presence of an excess amount of strong non-coordinating acid,
then the reaction proceeds faster, and also a purple complex is formed, but the
color is much less intense.
Without the extra acid, there really is a new complex with chromium(III). This
complex reacts with ammonia, giving a nice green solution.
EXPERIMENT 69
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When hydrated sulfate-salts are heated, which only loose water, then their
properties strongly change. The color changes, but also the solubility
properties change a lot. The sulfate salts loose water easily, but no acid
(H2SO4 or SO3).
EXPERIMENT 70
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Chromium trioxide dissolves well in acetone, but it does not react. When
sulphuric acid is added, then it does react and it can do so nearly
explosively!
EXPERIMENT 71
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Dichromate and chromate both quickly are oxidized by pure formic acid,
resulting in a fairly violent and exothermic reaction, in which a dark
purple/blue/grey compound is formed.
EXPERIMENT 72
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Hexavalent chromium is reduced to trivalent chromium by hypophosphite, but
there is no further reduction to chromium(II).
EXPERIMENT 73
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Thallium(I) chromate and thallium(I) dichromate both are insoluble (or at most
marginally soluble) in water. Thallium(I) is not a sufficiently strong reductor
to get the hexavalent chromium reduced.
EXPERIMENT 74
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Chromium(III) ions give a light green precipitate with iodate.
EXPERIMENT 75
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Chromium(III) oxide is extremely inert when it is calcined. It does not
dissolve in the common acids, nor in solutions of common bases. The solid,
however, can be oxidized by a solution of a bromate.
EXPERIMENT 76
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Sodium dichromate anhydrous dissolves in methanol quite well, but does not
react with it. When a little concentrated sulphuric acid is added, then
suddenly a very violent reaction occurs.
With potassium dichromate, this violent reaction does not occur. The latter is
nearly insoluble in methanol and hence it hardly can react with it.
EXPERIMENT 77
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Chromium trioxide (CrO3) dissolves in concentrated hydrochloric acid, giving a
dark brown liquid. When this liquid is heated, then some orange/brown chromyl
chloride is formed, which can easily be observed as a vapor above the liquid.
On further heating the hydrochloric acid is oxidized and the hexavalent
chromium is converted to green trivalent chromium.
EXPERIMENT 78
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Dichromate ion oxidizes thiosulfate easily in acidic media, but in neutral
media it only is oxidizing incompletely, and a solid compound is formed.
EXPERIMENT 79
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When phosphorus pentachloride is added to chromium trioxide, then a fairly
vigorous reaction occurs and exchange of oxygen and chlorine atoms occurs. The
two solids react with each other, forming liquid CrO2Cl2 and liquid POCl3.
EXPERIMENT 80
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Sodium sulfite is not capable of reducing CrO3, dissolved in acetyl chloride.
As soon as water is added, the red color of the hexavalent chromium disappears
and green/blue trivalent chromium is formed.
EXPERIMENT 81
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Chromium metal does not dissolve al all in concentrated nitric acid, not even
when the acid is heated. It does dissolve in concentrated hydrochloric acid and
also in moderately concentrated perchloric acid, but in the latter some heating
is required.
EXPERIMENT 82
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Cesium dichromate is very sparingly soluble in cold water, while cesium
chromate is much more soluble in cold water.
In warm water, the solubility of the dichromate is much higher.
EXPERIMENT 83
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Ethylacetate is in equilibrium with ethanol and acetic acid, even in dilute
aqueous solution with some free acid in it. Usually, making esters requires
rather forcing conditions, like mixing an alcohol and an organic acid and
adding this mix to concentrated sulphuric acid and then heating the mix. This
experiment nicely demonstrates that there is an equilibrium, also in water.
EXPERIMENT 84
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Chlorosulfonic acid is an extremely reactive compound. It reacts violently with
many salts of oxoacids.
End of results for 'Cr'