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Sodium dichromate is the inorganic compound with the formula Na 2 Cr 2 O 7.However, the salt is usually handled as its dihydrate Na 2 Cr 2 O 7 ·2H 2 O.Virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt. [1]
ion has a similar radius (63 pm) to Al 3+ (radius 50 pm), and they can replace each other in some compounds, such as in chrome alum and alum. Chromium(III) tends to form octahedral complexes. Commercially available chromium(III) chloride hydrate is the dark green complex [CrCl 2 (H 2 O) 4]Cl.
aluminium: 7429–90–5 AlAs: aluminium arsenide: 22831–42–1 AlB 2: aluminium diboride: 12041–50–8 AlB 12: aluminium dodecaboride: 12041–54–2 AlBr 3: aluminium bromide: 7727–15–3 AlBr 3 •6H 2 O: aluminium bromide hexahydrate: 7784–11–4 Al(CHO 2) 3: aluminium formate: 7360–53–4 AlCl 3: aluminium chloride: 7446–70–0 ...
Sodium chloride – NaCl; Sodium chlorite – NaClO 2; Sodium cobaltinitrite – CoN 6 Na 3 O 12 [207] Sodium copper tetrachloride – Na 2 CuCl 4; Sodium cyanate – NaCNO; Sodium cyanide – NaCN; Sodium dichromate – Na 2 Cr 2 O 7 ·2H 2 O; Sodium dioxide – NaO 2; Sodium dithionite – Na 2 S 2 O 4; Sodium ferrocyanide – Na 4 [Fe(CN) 6 ...
The hydrogen chromate ion may be protonated, with the formation of molecular chromic acid, H 2 CrO 4, but the pK a for the equilibrium H 2 CrO 4 ⇌ HCrO − 4 + H + is not well characterized. Reported values vary between about −0.8 and 1.6. [4] The dichromate ion is a somewhat weaker base than the chromate ion: [5]
For lab and small scale preparations a mixture of chromite ore, sodium hydroxide and sodium nitrate reacting at lower temperatures may be used (even 350 C in the corresponding potassium chromate system). [2] Subsequent to its formation, the chromate salt is converted to sodium dichromate, the precursor to most chromium compounds and materials. [3]
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Sodium dichromate is sometimes used because of its higher solubility (50 g/L versus 200 g/L respectively). The use of dichromate cleaning solutions is now phased out due to the high toxicity and environmental concerns. Modern cleaning solutions are highly effective and chromium free. [93]