Arrange these events in the history of photographic permanence in chronological order.

1. Herschel identifies hyposulphite of soda as a solvent for silver salts, 1819
2. Herschel passes the fixer to Talbot for photogenic drawings, 1839
3. Warnings about residual hypo and fading become routine in the manuals, late nineteenth century
4. The Image Permanence Institute is founded at Rochester, 1985
5. ISO 18916, the Photographic Activity Test, is published, 2007

The gap between the third and fourth items is a century in which the problem was known and unmeasured. Permanence became a science rather than a set of warnings only when someone built the laboratory to test it, and the standards followed from the laboratory rather than the other way round.