A silver ion sequester and release agent is described which comprises a
silver ion exchangeable material of the formula:
M(H.sub.1-x-y Ag.sub.x M'.sub.y PO.sub.4).sub.2.nH.sub.2 O;
where M is Zr, Ti, Sn, Ge or Hf or any combination thereof; M' is an Alkali
or alkaline earth metal; x is a number from 0.10 to 0.80; y is a number
from 0.15 to 0.85; (x+y) is a number from 0.25 to 0.95; and n is a
rational number between 0 and 10. Processes for preparing such silver ion
sequester and release agent material are also described comprising
combining in an aqueous medium a crystalline or amorphous metal hydrogen
phosphate ion exchange host material of the formula
M(HPO.sub.4).sub.2.nH.sub.2 O with less than 2 molar equivalents of silver
ions relative to the amount of ion exchange host material such that silver
ions are exchanged for protons in the host material, and adding a base
compound to the aqueous medium to achieve a pH of at least 4.4 and
sequester at least 95% of the combined silver ions into the host material.
Further described are photographic elements comprising a support bearing
one or more hydrophilic colloid layers including at least one photographic
silver halide emulsion layer, wherein one or more layers contain such a
silver ion sequester and release agent which sequesters silver ions prior
to photographic processing and releases silver ions upon exposure to
photographic processing solutions.
