Dictionary.com
definitions

platinum black

noun Chemistry.
  1. a black powder consisting of very finely divided metallic platinum, used as a catalyst, especially in organic synthesis.

Origin of platinum black

First recorded in 1850–55
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for platinum black

platinum black

noun
  1. chem a black powder consisting of very finely divided platinum metal. It is used as a catalyst, esp in hydrogenation reactions
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012