  White dwarfs with metal lines in their spectra act as signposts for post-main
sequence planetary systems. Searching the Sloan Digital Sky Survey (SDSS) data
release 12, we have identified 231 cool (<9000 K) DZ white dwarfs with strong
metal absorption, extending the DZ cooling sequence to both higher metal
abundances, lower temperatures, and hence longer cooler ages. Of these 231
systems, 104 are previously unknown white dwarfs. Compared with previous work,
our spectral fitting uses improved model atmospheres with updated line profiles
and line-lists, which we use to derive effective temperatures and abundances
for up to 8 elements. We also determine spectroscopic distances to our sample,
identifying two halo-members with tangential space-velocities >300 kms-1. The
implications of our results on remnant planetary systems are to be discussed in
a separate paper.
