Abstract: Photographic silver halide emulsions which have their sensitivity increased by the addition of sulfur-substituted isothioureas of the formula; ##STR1## where R, R.sub.2, and R.sub.3 are organic radicals and R.sub.1 is an organic radical or H.

Abstract: Photographic colloid-silver halide emulsions are chemically sensitized by digestion at pH.gtoreq. 7 and the addition prior to or during digestion of at least one organophosphine sulfide of the general formula: ##STR1## WHEREIN (A) R is individually selected from the group consisting of hydrogen and a monovalent organic radical; m is 0, 1 or 2; and not more than one of said R's is hydrogen when m is 0; X represents a group having the formula: ##STR2## wherein Z is a divalent organic radical, n is 0 or 1, or (B) X.sub.m and R.sub.3-m together comprise a single trivalent heterocyclic radical.

Abstract: Photographic colloid-silver halide emulsions have their sensitivity increased by the addition of at least one organo-phosphine chelate of a palladium or platinum metal salt.

Abstract: Photographic colloid-silver halide emulsions are chemically sensitized by the addition prior to or during digestion of at least one trithiocarbonate compound of the general formula: ##STR1## wherein R is a tertiary alkyl radical having from 4 to 16 carbon atoms and R' may be the same as R or an aryl or an alphyl radical containing 1 to 3 aryl groups which may be substituted or unsubstituted.

Abstract: Photographic silver halide emulsions are prepared which have their sensitivity increased by the addition of hexathiocane thiones having the basic structure: ##STR1## where R is an alkyl, unsaturated alkyl, or a saturated cyclic group, and R.sub.1 is aryl or substituted aryl.

Abstract: Photographic elements comprising a silver halide emulsion layer give less fog in negative type emulsions and increased speed in direct-positive emulsions when said emulsions are developed in the presence of an organic heterocyclic or thioaryl-substituted tertiary phosphine.

Abstract: Photographic elements having a radiation-sensitive, colloid - silver halide emulsion layer and a contiguous light-insensitive layer containing an oxidizing agent selected from the group consisting of iodine and potassium iodate.

Abstract: 1,4,7,10-Tetraazatetracyclo[5.5.1.0.sup.4,13.0.sup.10,13 ]tridecane -tridecane which can reversibly and successively add two moles of acids to form conjugate acids, can be made by condensation of 1,4,7,10-tetraazacyclododecane with ethyl orthocarbonate or by the condensation of 2,3,5,6-tetrahydro-1H-imidazo[1,2-a]imidazole with ethyl bis(2-chloroethyl)carbamate followed by acid hydrolysis. The salts with acids having photographically innocuous anions can be used in developers for silver halide emulsion to reduce fog, and can be used in the emulsions themselves as sensitizers.