$FeCr _{2} O _{4}+ Na _{2} CO _{3}+ O _{2} \rightarrow A + Fe _{2} O _{3}+ CO _{2}$
$A + H ^{+} \rightarrow B + H _{2} O + Na ^{+}$
$+8 CO _{2}$
$2 Na _{2} CrO _{4}+2 H ^{+} \rightarrow \underbrace{ Na _{2} Cr _{2} O _{7}}_{ B }+2 Na ^{+}+ H _{2} O$
(પરમાણ્વીય ક્રમાંક: $Ni = 28, Ti = 22, $$Cr = 24, Co = 27$)