Hi Raghu,
Another chemical test known for seed viability is Indigo Carmine (IC) test, it takes 2 to 30 hours for staining depending on variety of seeds. Here, only dead tissue takes the stain. IC staining has been reported for Pinus silvestris and Picea abies seed.
Acid Fuchsin is another chemical for testing seed viability and it also takes 24 hrs for staining the non-viable tissue or embryos red (reported for orchid seeds).
TZ has been widely accepted and reliable among chemical seed viability tests.
Hope this helps you.
Thanks.