How to make Sodium dichromate
Note that the chromate ion $\ce{CrO4^{2-}}$ has chromium in the +6 oxidation state like dichromate $\ce{Cr2O7^{2-}}$. Chromate is yellow, dichromate is orange. 

From the Wikipedia article on sodium chromate: sodium chromate is formed by reaction of dichromate with hydroxide:

$$\ce{Na2Cr2O7 + 2NaOH -&gt; 2Na2CrO4 + H2O}$$

You may be making sodium dichromate, but the strongly basic conditions are converting it to sodium chromate.