Editing Osmium tetroxide (section)

==Physical properties==
[[File:OsO4structure.png|thumb|left|Crystal structure of OsO<sub>4</sub><ref name=s1/>]]

Osmium(VIII) oxide forms [[monoclinic]] crystals.<ref name=s1/><ref name=niosh/> It has a characteristic acrid [[chlorine]]-like odor.  The [[chemical element|element]] name osmium is derived from ''osme'', [[Greek language|Greek]] for ''odor''. OsO<sub>4</sub> is volatile: it [[sublimation (chemistry)|sublimes]] at [[room temperature]]. It is soluble in a wide range of organic solvents. It is moderately soluble in water, with which it reacts reversibly to form osmic acid (see below).<ref name=thompson>{{ cite web | author = Thompson, M. | publisher = [[Bristol University]] | title = Osmium tetroxide (OsO<sub>4</sub>) | url = http://www.chm.bris.ac.uk/motm/oso4/oso4h.htm | access-date = 2012-04-07 }}</ref> ''Pure'' osmium(VIII) oxide is probably colourless;<ref>{{ cite book |author1=Butler, I. S. |author2=Harrod, J. F. | title = Inorganic Chemistry: Principles and Applications | year = 1989 | publisher = Benjamin / Cummings | isbn = 978-0-8053-0247-9 | page = 343 | url = https://books.google.com/books?id=Nd3vAAAAMAAJ | access-date= 2012-04-07 }}</ref> it has been suggested that its yellow hue is attributable due to [[osmium dioxide]] (OsO<sub>2</sub>) impurities.<ref>{{ cite book | author = Cotton, F. A. | title = Advanced Inorganic Chemistry | edition = 6th | url = https://books.google.com/books?id=U3MWRONWAmMC | year = 2007 | publisher = J. Wiley | location = New Delhi, India | isbn = 978-81-265-1338-3 | page = 1002 }}</ref> The osmium tetroxide molecule is tetrahedral and therefore nonpolar. This nonpolarity helps OsO<sub>4</sub> penetrate charged cell membranes.