Mache (symbol ME from German Mache-Einheit, plural Maches) is a unit of volumic radioactivity named for the Austrian physicist

Heinrich Mache Heinrich Mache (27 April 1876 – 1 September 1954) was an Austrian physicist. He won the Haitinger Prize of the Austrian Academy of Sciences in 1915. Life Born in Prague, after his secondary school studies, Mache completed the first year of ...

. It was defined as the quantity of

radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...

(ignoring its

daughter isotope In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps (de ...

s; in practice, mostly radon-222) per litre of air which ionises a sustained current of 0.001 esu (0.001 StatAmpere). 1 ME = 3.64 Eman = 3.64×10⁻¹⁰ Ci/L = 13.4545 Bq/L.

References

Units of radioactivity Obsolete units of measurement {{measurement-stub