Editing Platinum (section)

===Halides===
Hexachloroplatinic acid mentioned above is probably the most important platinum compound, as it serves as the precursor for many other platinum compounds. By itself, it has various applications in photography, zinc etchings, [[Indelible ink#Indelible ink|indelible ink]], plating, mirrors, porcelain coloring, and as a catalyst.<ref name="krebs">{{cite book|title = The History and Use of our Earth's Chemical Elements|author = Krebs, Robert E.|chapter = Platinum|pages = [https://archive.org/details/historyuseofoure00kreb/page/124 124–127]|publisher = Greenwood Press|date = 1998|isbn = 978-0-313-30123-0|chapter-url = https://archive.org/details/historyuseofoure00kreb/page/124}}</ref>

Treatment of hexachloroplatinic acid with an ammonium salt, such as [[ammonium chloride]], gives [[ammonium hexachloroplatinate]],<ref name="Kauuf">{{Cite book|first1 = George B.|last1 = Kauffman|author-link = George B. Kauffman |date = 1967|volume = 9 |pages = 182–185|doi = 10.1002/9780470132401.ch51|last2 = Thurner|first2 = Joseph J.|last3 = Zatko|first3 = David A.| title=Inorganic Syntheses | chapter=Ammonium Hexachloroplatinate(IV) |isbn = 978-0-470-13240-1}}</ref> which is relatively insoluble in ammonium solutions. Heating this ammonium salt in the presence of hydrogen reduces it to elemental platinum.<!--Platinum is often isolated from ores and recycled thus.<ref>Cotton, S. A. [https://books.google.com/books?id=6VKAs6iLmwcC&pg=PA78 Chemistry of Precious Metals], Chapman and Hall (London): 1997. {{ISBN|0-7514-0413-6}}.</ref> Neither the text nor reference fit here--> [[Potassium hexachloroplatinate]] is similarly insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by [[gravimetry]].<ref>{{cite journal|first1 = G. F.|last1 =Smith |first2=J. L.|last2 = Gring|title = The Separation and Determination of the Alkali Metals Using Perchloric Acid. V. Perchloric Acid and Chloroplatinic Acid in the Determination of Small Amounts of Potassium in the Presence of Large Amounts of Sodium|journal = [[Journal of the American Chemical Society]]|date = 1933|volume = 55|issue = 10|pages = 3957–3961|doi = 10.1021/ja01337a007|bibcode =1933JAChS..55.3957S }}</ref>

When hexachloroplatinic acid is heated, it decomposes through [[platinum(IV) chloride]] and [[platinum(II) chloride]] to elemental platinum, although the reactions do not occur stepwise:<ref>{{cite journal|first1 = A. E.|last1 =Schweizer|first2 = G. T.|last2 =Kerr|title = Thermal Decomposition of Hexachloroplatinic Acid|journal = [[Inorganic Chemistry (journal)|Inorganic Chemistry]]|date = 1978|volume = 17|issue = 8|pages = 2326–2327|doi = 10.1021/ic50186a067}}</ref>

: {{chem2|(H3O)2PtCl6*''n''H2O <-> PtCl4 + 2 HCl + (''n'' + 2) H2O}}
: {{chem2|PtCl4 <-> PtCl2 + Cl2}}
: {{chem2|PtCl2 <-> Pt + Cl2}}

All three reactions are reversible. [[Platinum(II) bromide|Platinum(II)]] and [[platinum(IV) bromide]]s are known as well. [[Platinum hexafluoride]] is a strong oxidizer capable of [[dioxygenyl#Synthesis|oxidizing oxygen]].