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U.S. conducts tests to improve acidity standards. Washington, D.C. June 16. At the National Bureau [of] Standards, Dr. Walter J. Hamer is making very accurate electrometric measurements

Library of Congress · 1937 · Harris & Ewing

A chemist in shirtsleeves reaches across a bench of glass cells and rubber tubing, round-bottomed flasks hanging at its front and glass carboys ranked on the shelf above.
From the archive · Library of Congress · 1937 U.S. conducts tests to improve acidity standards. Washington, D.C. June 16. At the National Bureau [of] Standards, Dr. Walter J. Hamer is making very accurate electrometric measurements Harris & Ewing

Library of Congress, Prints & Photographs Division, Harris & Ewing Collection, LC-DIG-hec-22864 No known restrictions on publication. Archive record ↗ · Rights

Source Archival record · verify at Library of Congress ↗

Walter Hamer at the National Bureau of Standards, making the measurements that fixed the pH scale. Every acidity figure on this site is quoted against standards somebody had to establish first, in a room like this, by hand.

Shows: Where a water-quality number comes from before anyone samples a river: the calibration.

What this does not let you conclude: Any river, any sample, any Colorado water. This is metrology, upstream of every reading we publish. 16 June 1937.

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