Hardening of gelatin-containing layers

A method of hardening gelatin which comprises contacting gelatin with a compound of the formula:

• ##STR27## wherein:
• X is a member selected from the group consisting of O and S or X is absent,
• each Y independently is a member selected from the group consisting of O, S and a bond between R.sup.1 and P,
• each R.sup.1 independently represents an aliphatic group of up to 10 carbon atoms or the two R.sup.1 groups together represent the necessary atoms to complete a 5, 6 or 7-membered ring,
• R.sup.2 and R.sup.3 are independently members of the group consisting of hydrogen, cyclic groups and acyclic groups or R.sup.2 and R.sup.3 together represent the necessary atoms to complete a heterocyclic ring.

A photographic element comprising a silver halide emulsion layer and a gelatin layer containing photosensitive silver halide, said layer being hardened with a compound of formula:

• ##STR28## wherein:
• X is a member selected from the group consisting of O and S or is absent,
• each Y independently is a member selected from the group consisting of O, S and a bond between R1 and P,
• each R.sup.1 independently represents an aliphatic group of up to 10 carbon atoms or the two R.sup.1 groups together represent the necessary atoms to complete a 5, 6 or 7-membered ring,
• R.sup.2 and R.sup.3 are independently members of the group consisting of hydrogen, cyclic groups and acyclic groups or R.sup.2 and R.sup.3 together represent the necessary atoms to complete a heterocyclic ring.