Defying Stereotypes: Sir Humphry Davy

If a biographer of Humphry Davy wanted to reinforce the scientist-stereotype, he would emphasize how a young Davy was turned on to chemistry by reading Lavoisier’s book and how he was discharged from an apothecary for causing explosive reactions. He would mention his bad habit of inhaling gases, which probably helped shorten his life to 51 years.  Most importantly the biographer would highlight Davy’s discovery of seven chemical elements, more than anyone in history except for the discoverers of synthetic nuclear elements, which I find less exciting.

Davy’s early electrolysis equipment Credit: J & J Marshall

And the details of Davy’s discoveries are indeed stimulating for aficionados of chemistry. He first attempted to obtain elements by decomposing saturated alkali solutions. It’s easy for us to understand why such an attempt was in vain. But the concept of ions was almost a century away, so he could not have possibly foreseen that water  generates hydrogen ions, which attract electrons better than any alkali ion. Yet he was clever enough to then try it without water, to use the solid salts themselves, exposing them to air just enough to make their surface conduct.  Instead of failing like others who had heated the solids as if they were akin to oxides of mercury, Davy applied a battery’s current to potash. And it worked! Even when he switched the wires around,  he would always observe effervescence at the positive pole. and at the opposite pole, pearls of metal briefly appeared. Then some globules tarnished while others exploded in the air.  If water was added to the metal, the result would be just as dramatic:  he would get hydrogen gas, which in the presence of potassium, burnt with a lovely lavender light.

Of course there are other positive characteristics associated with the scientist-stereotype. The biographer would have to not only outline his discoveries but discuss how Davy  considered the possibility that he was wrong, just in case his substances weren’t new elements. Indeed Davy did switch his platinum electrode with other materials to check if the material itself was involved in the reaction. But copper, gold, silver and lead alloys all yielded the same result. When others like Gay Lussac had suspected that the hydrogen was coming out of the potassium, so named because it came from potash, Davy revealed that in the absence of water, no gas could come out of potassium or sodium. He really had discovered new elements. Eight years later, in 1815, Davy saved lives by inventing a miner’s safety lamp. Its gauze’s holes let oxygen in, and when they were of the right size, the metal surface cooled and blocked the spread of the flame, preventing the ignition of explosive methane from deep coal mines.

On the left is Davy’s lamp. On the right is a an earlier prototype that did not work so well. From the Royal Institution’s archives. Photo by Paul Wilkinson.
M0004638 Portrait of Sir Humphry Davy, 1st Baronet, FRS (1778 – 1829),
Humphry Davy from Wikimedia Commons

So what should a biographer add about Davy, so as not to reinforce the common image the public has of scientists: Davy’s enthusiasm for fishing? A mention of his good looks, the reason that some ladies attended his public lectures? The most pronounced atypical characteristic about Davy is that he wrote poetry throughout his life. J. Z. Fullmer writes ,

In his science, he had searched into the hidden and mysterious ways of
nature. In his poetry he had truly worshiped and adored Nature’s
“majesty of visible creations.” He was Philosopher, Sage, and Poet.

In one of his notebooks Davy recorded the following. It’s not verse but certainly prose of a poetic nature:

To-day, for the first time in my life, I have had a distinct sympathy with
nature. I was lying on the top of a rock to leeward; the wind was high, and
everything was in motion; the branches of an oak tree were waving and murmuring to the breeze; yellow clouds, deepened by grey at the base, were rapidly floating over the western hills; the whole sky was in motion; the yellow stream
below was agitated by the breeze; everything was alive, and myself part of the
series of visible impression. I should have felt pain in tearing a leaf from one of
the trees.                                                     Memoirs  Volume 1 p113

If such an experience is the exception, it begs the question, is such a perception of the world among scientists any more rare than it is in the rest of the population? Poetry aside, the thing that scientists have in common is an above average interest and devotion to science. But like any other group, there are more differences within their kind than there are between them and other people.


The discovery of the elements. IX. Three alkali metals: Potassium, sodium, and lithium. Mary Elvira Weeks  J. Chem. Educ., 1932, 9 (6), p 1035.

The Poetry of Sir Humphry Davy. J. Z. Fullmer.  Chymia, Vol. 6 (1960), pp. 102-126
University of California Press.  :

Asimov’s Biographical Encyclopedia of Science and Technology. Second edition Isaac Asimov.



Why Only Five Platonic Solids in Our Geo-Bio-Chemical World?

The DNA-surrounding capsid of the cold virus and the atomic arrangement of  a certain allotrope of  boron consists of  20 triangles arranged in a three dimensional shape known as a icosahedron.

If you form a three-dimensional structure with 8 triangles, you get an octahedron. An example is the molecular structure of the electrical insulator and potent greenhouse gas, sulfur hexafluoride, SF6. It can also appear in the mineral pyrite.

If you limit the number of triangles to four, you get a tetrahedron. The tetrahedral silicate unit,  SiO42- , is the basic component of most silicates in the Earth’s crust. On our planet’s surface, any time carbon makes four single bonds with other carbons or other elements in a wide variety of life’s hydrocarbons, we also get a tetrahedral arrangement. This allows the four bonding pairs of electrons to get as far from each other as possible.

Changing polygon, we can use 6 squares to make a cube. The similarly-sized ions of cesium and chloride can form an arrangement where each whole ion centers 8 vertices occupied by an ion of the opposite charge. But viewed within the lattice, the boundaries of the cube are such that only 1/8 of each ion is at a vertex. Given that there are 8 vertices, this maintains the ratio of one cesium for every one chloride ion. In the mineral halite, which is composed of NaCl, the chloride ion is considerably bigger than the sodium. They don’t pack into a cube in the same manner, but overall they still form the same shape.

Then there is the dodecahedron, consisting of a dozen pentagons. Cubes of pyritohedron form the macro-illusion of a dodecahedron, but otherwise this “perfect” solid is rare in nature.pyrite_really_cubes_molecular

Are there more than these 5 possible perfect or Platonic solids? No. But why?

There is a relationship that holds for all solids of this type. If you let V represent the number of vertices, E = number of edges and F = the number polygonal faces, slide1-l

you will observe that in a tetrahedron V= 4, E = 6 and F = 4.

For a cube, download

Notice that for both solids, the following simple formula(called Euler’s Formula)holds true:

V + F – E = 2.                                 Equation (1)

That doesn’t constitute a proof for why it should apply to all cases, but you can find one here. We can use this formula to prove that there are only a limited number of Platonic solids.

First let’s introduce two other variables, N = the number of sides in a polygonal face and R = number of edges that meet at a vertex.

Since each edge is shared by two vertices, if we multiply R by the number of vertices,V , and divide by two, we will get the total  number of  edges:

RV / 2  = E;   Solving for V we get

V = 2E / R                                        Equation (2)

The number of edges can also be obtained by the number of faces. Each face has one edge for each of the number of sides, N. But each edge is shared with another face, so again not to count things twice:

NF / 2 = E.   Solving for F we get

F = 2E / N                                        Equation (3)

Substituting equations (2) and (3) into equation 1:

2E / R  + 2E / N   – E = 2.     

Now divide each term by 2E:

1/R + 1/N1/2 = 1/E. 

We need at least three edges to get a 3D shape so R ≥ 3. Similarly to get a polygon, N ≥ 3. Interestingly N and R cannot simultaneously be greater than 3,  because as they create progressively smaller fractions, 1/R  and 1/N will add up to a maximum sum of 1/2 ( if R=N=4), which in the formula will yield 0 = 1/E.  

Letting N = 3,  if R = 3  then E = 6. Using this result and equation(3),  F = 2E/N = 2(6)/3= 4: the tetrahedron.

Having no choice due to the restriction we mentioned, we have to keep either N or R at 3 while increasing the other, so

letting N = 3,  if R = 4, E = 12 and F = 8, the octahedron. 

Reversing the values and letting N = 4 and R = 3, E = 12 and F = 2(12)/4= 6,  the cube.

We can then try the combinations of N= 3,  R= 5 and N= 5, R= 3, which will solve for the icosahedron ( E = 30; F = 20) and dodecahedron ( E = 30; F = 12), respectively.

But 5 is the limit because if we try values of 3 and 6:

1/3 + 1/6 – 1/2 = 0, which means the impossibility of no edges. A value larger than 6 yields a negative value for E.

Given that there are only these 5 solutions to Euler’s formula , then only five Platonic solids can exist in three dimensional space.

Up ↑