Chemical Samples

This collection of samples is a sudoku puzzle in disguise with the 9 unique characters being

1 2 3 5 6 7 8 C E

Solving the sudoku by standard rules gives the grid below.

Reading down the the highlighted diagonal gives the string EC2367518. Formatting it with dashes as clued at the top of the grid and 8 7 cluing the final answer word lengths.

EC 236-751-8

Which is the registration number for ALUMINUM NITRATE