The College of Physicians of Philadelphia Digital Library

Quartz Piezo Electrometer

About This Item

Title

Quartz Piezo Electrometer

Subject

Curie, Marie, 1867-1934
Curie, Pierre, 1859-1906
Piezoelectric devices.
Radiation--Measurement.

Description

Pierre Curie, husband of Marie Curie, built this piezo-electric apparatus around 1889. After years of use in the Curie laboratory, Marie Curie donated the device to The College of Physicians of Philadelphia on a visit in 1921. The device has been on display at the College since then, except for a brief time in 1988, when Museum staff discovered it to be radioactive and it had to be decontaminated.

This device is one of two original piezo machines that the Curies employed in their discovery of radium and polonium. As a forerunner to the modern dosimeter, it was one of the first tools to measure radioactivity. The other piezo device used by the Curies did not survive.

Within the brass box a thin piece of quartz crystal, sandwiched between two rods, suspends a small pan. When weights are added to the pan, the crystal is stressed, producing electric charge. This is the piezo-electric effect, discovered by Pierre Curie. Though the charge produced is small – in the pico-amperes – it is predictable and quantifiable as a function of the known weight added to the pan.

The Curies used this device to measure the activity of a radioactive substance – an important property to quantify as radiation treatments for cancer were developed. They measured radiation by attaching the piezo-electric apparatus and a radioactive source in a nearby ionization chamber to an electrometer. The amount of radioactivity was determined by adding and subtracting weights on the pan so that the current produced by the quartz matched the current produced by the radioactive substance.

The piezo-electric device pictured here is missing several elements; for example, electrical contact points are needed for the charge produced by the crystal to reach the electrometer (also not shown, nor is the ionization chamber for the radioactive substance).

Creator

Marie and Pierre Curie

Publisher

Digitized by the Mütter Museum of The College of Physicians of Philadelphia

Date

1889

Identifier

2013.9.1

Coverage

19th Century

Original Format

Wood, steel, glass, brass

Citation

Marie and Pierre Curie, “Quartz Piezo Electrometer,” The College of Physicians of Philadelphia Digital Library, accessed September 20, 2018, https://www.cppdigitallibrary.org/items/show/2593.