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1.
Oxide
Vanadium pentoxide (V 2 O 5 ) is one of the important compounds of vanadium.
Its color ranges from orange-yellow to deep red (generally orange-yellow), odorless, tasteless, toxic, and slightly soluble in water
.
V 2 O 5 is a catalyst for the oxidation of SO 2 to SO 3 for the production of sulfuric acid
V 2 O 5 can be obtained by thermal decomposition of NH 4 VO 3 .
2NH 4 VO 3 =V 2 O 5 +2NH 3 +H 2 O
V 2 O 5 is an amphoteric partial acid, easily soluble in NaOH, and also soluble in strong acids with larger concentrations
.
V 2 O 5 is dissolved in NaOH solution to obtain nearly colorless vanadate Na 3 VO 4 or metavanadate NaVO 3 solution; dissolved in strong acid, in acidic solution with pH<1, it can produce light yellow Vanadium dioxy cation VO 2+
V 2 O 5 is highly oxidizing and reacts with concentrated hydrochloric acid to generate chlorine gas
.
V 2 O 5 +6HCI=2VOCl 2 +Cl 2 +3H 2 O
The dark blue VO 2 can be slowly reduced by V 2 O 5 , and VO 2 dissolves in acid to generate blue VO 2+
.
KMnO 4 reacts quantitatively with VO 2+ in acid medium
V 2 O 3 is black, and VO is gray-black
.
Vanadium can also form many non-integral compounds with oxygen
Both Nb 2 O 5 and Ta 2 O 5 are white solids, amphoteric and slightly alkaline, low in activity, and do not interact with other acids except HF
.
The eutectic of Nb 2 O 5 , Ta 2 O 5 and NaOH respectively generates corresponding oxo acid salts
2.
Oxygenates
Vanadates include orthovanadates (such as Na 2 VO 4 ) and metavanadates (such as NaVO 3 )
.
N vanadate tetrahedral configuration; metavanadate VO .
3 - , is formed by tetrahedrally coordinated vertex co-oxo long chain structure
VO 4 3- or VO 3 - only exists in strong alkaline solutions.
As the pH decreases, it will gradually polymerize to form dimers (V 2 O 7 4- , colorless), trimers) V 3 O 9 3- , colorless) and decamer (V1 0 O 6 28- , orange-red) and so on
VO 2+ can be reduced to VO 2+ by Fe 2+ , I-, etc.
Oxalic acid can reduce VO 2+ to V 3+ , and some strong reducing agents can also reduce VO 2+ to V 2+ :
The pentavalent vanadium solution undergoes a peroxy chain transfer reaction with H 2 O 2 and the product and color are related to the acidity and alkalinity of the solution
.
It produces yellow [VO 2 (O 2 ) 2 ] 3- in alkaline and neutral solutions, and mainly produces red [V(O 2 )] 3 + in strong acid solutions
.
3.
Halides
The pentahalide of vanadium is only VF 5 , and the pentahalide of niobium and tantalum can be prepared by direct combination of metal and halogen
.
In addition, vanadium subgroup elements can generally form tetrahalides, trihalides and dihalides
.
VF 5 is a colorless liquid, VF 4 is a green solid, VF 3 is a yellow-green solid, and VCl 4 is a red liquid
.
Saws and tantalum halides are solid, NbF .
5 and TaF .
5 as a white, NbCl5 .
5 , Nbl .
5 , TaCl5 .
5 and TaBr .
5 as a yellow, NbBr .
5 as an orange, Tal .
5 black
.