The key to preserving the old, degrading paper of treasured, ageing books is contained in the smell of their pages, say scientists.

Researchers report in the journal Analytical Chemistry that a new "sniff test" can measure degradation of old books and historical documents.

The test picks up and identifies the chemicals that the pages release as they degrade.

This could help libraries and museums preserve a range of precious books.

The test is based on detecting the levels of volatile organic compounds.

These are released by paper as it ages and produce the familiar "old book smell".

"This unmistakable smell is as much part of the book as its contents," they wrote in the journal article.

Dr Strlic told BBC News that the idea for new test came from observing museum conservators as they worked.

"I often noticed that conservators smelled paper during their assessment," he recalled.

"I thought, if there was a way we could smell paper and tell how degraded it is from the compounds it emits, that would be great."

The test does just that. It pinpoints ingredients contained within the blend of volatile compounds emanating from the paper.

To read the complete article, see:Sniff test to preserve old books(http://news.bbc.co.uk/2/hi/science/nature/8355888.stm)