Also found in: Medical.
(named after the Austrian physicist H. Mache; 1876-1954), an obsolete unit of the concentration of radioactive nuclides. It is occasionally used in balneology (for the dosimetry of mineral waters and therapeutic muds) and in the dosimetry of natural gases (air). The concentration of radon in water or air is usually indicated in mache units. One mache unit is the amount of radioactive nuclide present in 1 liter of liquid or gas and capable of maintaining, through a-decay (without the participation of decay products), an ionization saturation current of 10-3 cgs units (3.336 ×10-13 A); 1 mache unit = 3.64 emans = 3.64 ×10-10 curies/liter.