Wednesday, March 23, 2011

Phosphorus, The Miraculous Bearer Of Light


"The Alchymist" by Joseph Wright of Derby (1771)

Several elements -- gold, silver, copper, mercury, lead, iron, tin, sulfur, and carbon -- were known since ancient times. Three more were discovered during the Dark Ages: antimony, arsenic and zinc. Phosphorus was first isolated in 1669 during the pre-dawn hours of the Enlightenment and it was the first element whose discovery was recorded in modern times. After a lapse of about a hundred years, new elements were rapidly discovered up until the last one, Francium, was found in 1939. New elements were of course still synthesized afterwards.

Van der Krogt retells the amazing story of Henning Brandt's discovery of phosphorus and its subsequent naming as the "light bearer" -- it's well worth a read. The above painting, called "The Alchymist" by Joseph Wright of Derby, depicts the special property displayed by elemental phosphorus: its chemiluminescence as it slowly burns in air. I once provoked a challenge over at Trooper York's as to whether Brandt had really discovered phosphorus. You can read that here. I think the notion that medieval alchemist Paracelsus actually discovered phosphorus is a Montana Urban Legend. Incidentally, I did learn researching this blog post that glowing phosphorus may indeed be an ancient phenomenon: see the story of the "will o' the wisp" here.

The Wright painting also reminds me of the covers of the old Aldrich Chemical Company catalogs. I wish that Alfred Bader would publish a collection of all the past covers. More of what I'm talking about can be found here.

Since the time of Brandt, better sources than putrefied urine have been found for the element, namely, bone.  Did you know that we may one day face a phosphate shortage?  Perhaps the time will come when we start to recycle people's bones.

I'll end with a recipe à la Trooper York for elemental phosphorus:

How to Make Phosphorus (ref)

1. Allow urine to sit in an open container for 7 days.

2. Mix two tablespoons of finely-powdered charcoal and two tablespoons of powdered cinnamon* into the urine and stir.

3. Pour the urine/charcoal dust and cinnamon mixture into a glass retort with a glass tube leading into a second beaker filled with plain water.

4. Heat the retort containing the urine mixture using your torch. Be sure to wear protective clothing, eye protection and a breathing mask.

5. Allow the vapors from the urine mixture to bubble through the plain water. A yellow or white waxy substance will collect in the bottom of your water beaker. This is phosphorus. Do not expose it to the air or it may ignite spontaneously. After being exposed to light your phosphorus should glow very brightly in the dark for several hours.
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* I'm not at all sure of the role of cinnamon here--perhaps as an anti-oxidant or an odor-masking agent for a very unsavory process.

2 comments:

  1. Robert Bunsen's invention of his eponymous burner enabled the rapid identification of new chemical elements.

    In 1861, Bunsen reported:

    Supported by unambiguous results of the spectral-analytical method, we believe we can state right now that there is a fourth metal in the alkali group besides potassium, sodium, and lithium, and it has a simple characteristic spectrum like lithium; a metal that shows only two lines in our apparatus: a faint blue one, almost coinciding with Sr, and another blue one a little further to the violet end of the spectrum and as strong and as clearly defined as the lithium line.

    Bunsen and Kirchhof had discovered cesium which they named after the Latin word caesium meaning "sky blue".

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  2. That is a classic thread linked at Trooper York. If you're not a member but would like to become one, email him.

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