The operator, after having been dabbling for some time in hypo, or pyro, or silver solution, gives his hands a wipe on the focusing cloth, and straightway sets about making an enlargement, ending up by blessing the manufacturer who sent him paper full of black stains and smears.

Bromides in quantities, as added to ammoniacal pyro, would reduce the sensitiveness to 1/10 or 1/20; will even retard the developing power almost entirely.

Within a short period sulphurous acid has become an important element in the preparation of an excellent pyro developer for gelatine plates; and as it is more or less unstable in its keeping qualities, some easy method of preparing a small quantity which shall have a uniform strength is desirable.

Edwin Lanham (A); 1Jun71; R506899. Professor Pyro.

Edwin Lanham (A); 1Jun71; R506899. Professor Pyro.

The plates require about three times as much exposure through the yellow screen as without it, and may be developed with the ordinary alkaline pyro-developer.