Atomistry » Chromium » Compounds » Lead Dichromate
Atomistry »
  Chromium »
    Compounds »
      Lead Dichromate »

Lead Dichromate, PbCr2O7

Lead Dichromate, PbCr2O7, containing 2 molecules of water of crystallisation, was described by Preis and Ray man, but its existence was subsequently denied.7 When a very concentrated solution of chromic acid (130 grams CrO3 per 100 c.c.) is electrolysed with a lead anode, a solution is obtained which evolves oxygen when kept, and deposits reddish-brown needles of lead dichromate, PbCr2O7. From the volume of oxygen evolved it appears that plumbic dichromate is formed and decomposes thus:

Pb(Cr2O7)2 = PbCr2O7 + 2CrO3 + O.

Mayer obtained lead dichromate by heating lead acetate with chromic anhydride and concentrated nitric acid under a reflux condenser; and Cox prepared the same salt by taking account of the fact that it is prone to hydrolysis and can only be formed in contact with a chromic acid solution of a certain concentration, which is 6.865 gram-molecules CrO3 per litre at 25° C. Thus by grinding together lead monoxide and chromium trioxide in saturated solution in the proportion of 2 gram-molecules of the former to 5 of the latter, lead dichromate is produced and may be obtained pure after washing with 7N solution of CrO3. It is a lustrous, red, crystalline powder.

Last articles

Tb in 6TVY
Si in 6Y7O
Rh in 6WRM
Rh in 6WRL
Ni in 6Y8Z
Ni in 6Y8Y
Na in 6ZXZ
Na in 7ACG
Na in 6YLS
Na in 6Y8Z
© Copyright 2008-2020 by
Home   |    Site Map   |    Copyright   |    Contact us   |    Privacy