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945216.  Sun Oct 14, 2012 1:07 pm Reply with quote

Posital wrote:
Potassium Permanganate

I always Youlgreave that to 'pomegranate'.

gerontius grumpus
945597.  Tue Oct 16, 2012 2:27 pm Reply with quote

At school we made a chemical volcano by dripping glycerol onto a pile of potassium permanganate crystals. It spontaneously combusts when there is enough glycerol.

945598.  Tue Oct 16, 2012 2:29 pm Reply with quote

there's a vid of this further up the thread gerontius.

dr bartolo
945767.  Wed Oct 17, 2012 10:50 am Reply with quote

Potassium maganate was formerly known as the "chameleon mineral" (aldough the term occasionaly refered to potassium permaganate)

945769.  Wed Oct 17, 2012 11:07 am Reply with quote

Heating potassium permanganate is the classic way of producing oxygen gas in the laboratory, this also produces potassium manganate, the solid changes from a deep purple to a green. I must admit I've never seen potassium manganate referred to as the chameleon mineral only potassium permanganate, but as it is made by heating potassium permanganate and that goes through a myriad of colour changes during its synthesis one more from purple to green is admissible.

945792.  Wed Oct 17, 2012 12:47 pm Reply with quote

dr bartolo wrote:
(aldough ...)

Hope your cold gets better soon.

dr bartolo
945946.  Thu Oct 18, 2012 10:49 am Reply with quote

BTW, one of the more curious uses of potassium permaganate was to stain paper- But the resulting stain was not purple as you might expect- The paper would turn brown. This property was exploited by restorers of books, who wished to make their restorations blend in with the book. Coffee, licorice or tobacco ewere also used, to similar effect

945975.  Thu Oct 18, 2012 1:14 pm Reply with quote

Thats the formation of the brown Mn(III) ion from the reduction of the purple Mn(VII) ion.

dr bartolo
946119.  Fri Oct 19, 2012 10:30 am Reply with quote

Paradoxically, not only was KMnO4 also used to stain paper, it was also used to remove stains. The process involved dipping the stained paper , firstly into a bath of KMnO4, then into a bath of
sulfurous acid (which removed the brown colour), then into a third bath of sodium hyposulfate to neutralise any remaining acid.
Perhaps the most ironic thing about this process, is that the sheets emerged form the bath a sparkling white - so white, that in order to make the pages look less out of place, the sheets had to be toned down with ... ... Potassium permaganate!

946149.  Fri Oct 19, 2012 12:00 pm Reply with quote

Classic redox reactions.

Prof Wind Up Merchant
947196.  Wed Oct 24, 2012 6:19 am Reply with quote

Sodium was called Natrium where the "Na" symbol comes from. Sorry for jumping ahead there.

Last edited by Prof Wind Up Merchant on Fri Nov 02, 2012 3:34 pm; edited 1 time in total

947198.  Wed Oct 24, 2012 6:30 am Reply with quote

Natrium is derived from an Egyptian word Natron.

"The English word natron is a French cognate derived from the Spanish natrón through Greek νίτρον nitron, which derived from the Ancient Egyptian word nṯry 'natron'. The modern chemical symbol for sodium, Na, is an abbreviation of that element's New Latin name natrium, which was derived from natron which refers to Wadi El Natrun or natron valley in Egypt from which natron was mined in ancient Egypt for use in burial rites."


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