That fixer is dead. Sulfur and perhaps some crystallized
ammonium thiosulfate are at the bottom of the bottles.
 Sodium thiosulfate in it's dry form will last many years. The
ammonium form as usually made available for the darkroom has a
much shorter life span.
 Those who are infrequently in the darkroom should consider
the sodium form. Used dilute it can be tossed after each use
with little wasted. That way it is always fresh, unused.    Dan