Tucked into the cumbersome title page of John Badcock's 1823 compendium is a phrase that should stop any modern reader cold. The book promises:

NUMEROUS USEFUL TESTS OF ADULTERATIONS IN THE MATERIALS THAT CONDUCE TO HEALTH

This was not a niche curiosity. In Regency London, food adulteration was endemic and often dangerous. Bread was bulked with alum, chalk, and ground bones. Tea leaves were stretched with dried hedge clippings dyed green with copper salts. Pepper was floor sweepings. Beer was "improved" with cocculus indicus, a fish-stunning poison. Pickles were greened with verdigris — literal copper corrosion. A working family's grocery basket was, statistically, partly fraud and partly slow poison.

Badcock's Domestic Amusements was a sequel to his earlier Philosophical Recreations, or Winter Amusements. In the preface he is unusually candid about why he wrote a second volume — he found the older authorities he had previously relied upon (he names Hooper, Salmon, Boyle, Lupton, Smith, and Imison) to be:

frequently found unintelligible, always insipid, and sometimes trifling. "Provide a,"—"You take a,"—"Take your—in your hand," formed the boundaries of the [instruction]

His complaint is essentially that the previous generation's science-for-the-home books had degenerated into vague parlor tricks. He wanted procedures specific enough that an ordinary householder could actually use them — including, crucially, to test whether their grocer was poisoning them.

What is forgotten today is not the chemistry itself — most of these tests still work — but the cultural expectation that an ordinary householder would perform them. The home cook of 1823 was expected to drop a bit of suspected bread into vinegar and watch for the effervescence that betrayed chalk; to boil pickle brine and look for the blue-green tinge that meant copper; to stir suspect tea into water and see whether the dye ran. Detecting fraud in your own pantry was a domestic skill on par with mending or preserving.

This responsibility evaporated in the late 19th century with the first pure-food laws — Britain's 1860 and 1875 Adulteration Acts, and in the United States the 1906 Pure Food and Drug Act that birthed the FDA. We outsourced the chemistry, and rightly so. But we also lost the habit of skepticism toward our food supply, and the small competence of being able to verify it ourselves.

• Modern echoes: home water testing kits, at-home lead swabs for imported ceramics, and the recent revival of melamine tests for milk after the 2008 Chinese infant-formula scandal all live in Badcock's lineage.
• The 2008 scandal in particular — adding nitrogen-rich melamine to fake high-protein readings — is structurally identical to alum in bread: a cheap adulterant that fools the standard quality check.

Badcock would have recognized it immediately, and probably written a chapter about it.