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Home , Davy lamp, Electrolysis, Humphry Davy

Barry K James December 2017, HumpfryDavyRevC.ppt

CANNOCK CHASE U3A SCIENCE & TECHNOLOGY GROUP

A Famous Scientist: Sir 1st Baronet PRS MRIA FGS

Brilliant Experimentalist, & Poet JAN 2018 WHAT YOU PROBABLY KNOW DAVY FOR…

 In 1815, Davy began the work that established his popular fame.

 In response to a series of mine disasters in the north-east, he designed a that would light collieries without causing explosions.

WHAT YOU PROBABLY DON’T KNOW ABOUT HUMPHRY DAVY.

 By 1818, Davy was known across Europe as a genius.  He invented and helped stop the sheathed warships of the from corrosion with a sacrificial .  He showed and were elements.

 He experimented with the effects of Nitrous N2O.  Melted a with a lens, concluding it to be .  Davy concluded that contained replaceable ; hydrogen that could be replaced by when reacted.  E.g. H+Cl- + Na+OH- = a +  He formulated chemicals to manufacture gunpowder.  awarded him a medal and the Prince Regent made him a baronet. AND THERE’S LOADS MORE YOU PROBABLY DIDN’T KNOW.  He pioneered using from a battery of Voltaic piles.  He discovered 9 new elements using electrolysis around 1808.  Invented a very early form of , and the arc light. (Before Edison!)  Was a founding member of the Geological Society in 1807.  In 1804 Davy became a Fellow of the Royal Society, later being the President in 1820.  Davy employed a …  He was also a poet (over 160 manuscripts).  And there’s the miner’s lamp of course.

DAVY’S EARLY YEARS… THE PNEUMATIC INSTITUTE

 Born in in 1778. Apprenticed to a surgeon after schooling.

 Practised chemistry at Bartholomew’s hospital near Hayle, but no Uni.

 Davy appointed to the Pneumatic Institute in 1798 moving to .

 It was started by in 1793, a physician from Shifnal, Shropshire. Davy was asked to be an assistant.

 Formed to study the medical effects of the gases that had recently been discovered, hoping to cure illnesses with them.

 Hoped to cure sufferers from tuberculosis and respiratory complaints by inhaling gases like hydrogen and and .

 Even took part because of his son dying from TB. He designed much apparatus and techniques necessary to produce and administer various gases. Apparatus designed by James Watt in preparation of the

 Davy headed the laboratories from 1798, and started

experimenting with N2O, nitrous oxide.

THE RI

 RI was founded by the president of Royal Society in 1799 to use science for practical purposes. Labs were in the basement.

 Few elements had been discovered in the the 1800’s, nor the table of elements.

 The obtained the services of the twenty two year old Humphry Davy in 1801 with a promise of funding for his work in “galvanism”.

 The RI began to stage spectacular and entertaining, not to say dangerous, demonstrations of scientific experiments.

 His lectures were wildly popular with over 500 attending which created the necessity for the first one way street in London.

 Davy associated with lords and ladies to gain funding for his battery experiments. Davy loved the showmanship in his lectures.

 Davy became a full lecturer & Professor of Chemistry in1802 at the RI.

 Davy’s Nitrous Oxide antics proved to be a good lecture…

A side effect of N2O? New Discoveries in Pneumaticks! or - an Experimental Lecture on the Powers of Air

DAVY & NITROUS OXIDE

 Joseph Priestly first heated filings dampened with nitric to

produce N2O. Called it phlogisticated nitrous air.  Davy used nitrate of ammoniac bubbled in a heated retort to produce the N2O.

 The escaping gas was collected in a hydraulic bellows before seeping through water into a reservoir tank from which a sealed box was filled.

 While seated in the box breathing deeply, Davy felt the effects from his previous experiments. Then inhaled some more gas after exit.

 It had a sweet taste, followed by a gentle pressure in the head as he continued to inhale. Within seconds the sensation of soft, probing pressure had extended to his chest, and the tips of his fingers and toes. This was accompanied by a vibrant burst of pleasure.

 Nitrous oxide made Davy laugh when inhaled.

 So he named it “laughing gas”.

The machinery used to create his experimental gases HEALTH & SAFETY. WHAT HEALTH AND SAFETY?

 His experimenting eventually proved N2O had no cure for diseases.

 N2O was also thought useful for performing surgical operations to reduce pain. His thoughts were ignored.

 Anaesthetics were not regularly used in medicine or dentistry until decades after Davy's death.

 Davy ran considerable risks inhaling gases like , acidic gases, and trichloride explosions around 1812.

 Losing two fingers and an eye in two separate explosions with it. ”It is not safe to experiment upon a globule larger than a pin's head”.

 "seemed sinking into annihilation." Davy faintly articulated, "I do not think I shall die”.

 Davy was able to take his own pulse as he staggered out of the laboratory, and he described it as "threadlike and beating with excessive quickness".

 And PPE? What protection equipment? DAVY’S LECTURES AT THE RI

And he wrote books too DAVY & ELECTRICITY AT THE RI

 Davy was a pioneer in the field of Electrolysis.

 In 1800, the Italian scientist had introduced the first pile, which is what Davy used.

 The pile was 2 different metal discs (Cu + Zn) with cloth soaked in as an . Each disc pair was ~0.76V.

 Voltaic piles were placed together in a trough by William Cruickshank of Woolwich. We know this now as a battery.

 Theoretically no limit to the or energy. Davy used 2000 piles.

 Plenty of practical limits though, as we know!

 Davy used these trough batteries for his electrolysis experiments.

THE ELECTROLYSIS EXPERIMENTS

 Davy used the Voltaic piles to split common compounds for what is now called electrolysis

 This produced many new elements and became a new electro- chemistry.

 He used common molten salts like KOH (caustic ) to discover this way in 1807.

 Then followed from molten sodium .

 During the first half of 1808, Davy did further electrolysis experiments on “alkaline earths” including lime, magnesia, strontites and barytes.

 Davy identified 9 elements by these methods, , , , and etc.

 He also identified Chlorine and Iodine as elements.

 Davy loved demonstrations which involved explosions and spectacular events at the RI. Magnesium for instance.

 This made science memorable to people at the time. DAVY & THE LIGHT BULB

 In 1802, Humphry Davy had what was then, the most powerful electrical battery in the world at the Royal Institution.

 With it, Davy created the first incandescent light by passing through a thin strip of platinum.

 Platinum was chosen because the metal had an extremely high melting point. It was neither sufficiently bright nor long lasting enough to be of practical use, but demonstrated the principle.

o By 1808 he was able to demonstrate a much more powerful form of electric lighting to the RI in London. It was an early form of arc light which produced its illumination from an created between two charcoal rods. It used a 2000 pile battery. The Massey Pillars AND NOT JUST A CHEMIST…

 Although Davy was a scientist, he also wrote poetry from his youth to just before his death.  He associated with Coleridge and Wordsworth.  Davy thought both chemistry and poetry transformed the world.  It is estimated that there are over 150 poems written by him during his lifetime, held at the RI. THE PROBLEM

 Anyone for tea?

 After Tea: The FireDamp Solution THE FIREDAMP PROBLEM

 Robert Gray, a rector in County Durham, and other mine owners were concerned about fatalities in North East mines.

 The explosions were caused by the ignition of

“Firedamp”, now known as , CH4, killing 100’s of miners in the 1800’s.

 James Wilkinson, a lawyer from Durham formed a society for preventing accidents in mines in 1813. WHAT NEXT?

 The Wilkinson society approached Davy at the RI about preventing explosions from methane in 1815.  Davy thought immediately about a lamp that would not ignite the gas rather than ventilate or neutralise.  Davy stayed the night near a colliery at Hebburn where he was lent a safety lamp that Dr William Clanny had invented back in 1812.  Used a bellows into an enclosed combustion chamber, stopping igniting surrounding gas.

THE COMPETITORS

 Bellows lamp that had been invented by a Dr William Reid Clanny.  Thought of not much practical use in a mine, because it would take a person to operate it.  But Clanny was awarded a medal for the lamp in 1816 by the Arts Society.

’s version of lamp.  Developed at same time as Davy’s.  His 2nd version had inlet tubes.  Stephenson eventually gave up, to concentrate on locomotion.

DAVY’S DEVELOPMENTS

 Davy collected samples of the firedamp gas and sent bottles of it to the RI in London.  He deduced that it was a hydrocarbon from experiments, CH4.  He found it would not explode through small tubes of 1/8th of an inch. (Stephenson also found this)  He also made the exhaust exit of narrow tubes and eventually added bellows.  He found that as the methane slowly entered the tubes, the flame would burn more brightly, exhausting the limited inlet oxygen, but not cause an explosion, as the flame would go out.  This was the basis of his first 3 lamp designs.

MORE MODIFICATIONS…

 Davy changed the chimney shape to include a valve actuated by a bimetallic strip. Too much heat would close the valve.  Then an inlet valve actuated by heat.

 Later the inlet tubes increased to six, each 1½” long.  Then a liquid seal at the top  Then “fire sieves” instead of tubes.

FINALLY, THE GAUZE

 Davy made a breakthrough by placing a gauze mesh over the flame.  “Forms an explosion sieve, and separates flame from air, yet emits light”.  If there was methane the gas would burn steadily blue and controlled inside the gauze.  But the flame would not penetrate the gauze “like a bird in a cage”.  So the methane now helped to see better without explosions.  But there is no record of how he came to this idea.

SO, HERE’S THE EVOLUTION LINE UP

THE DISPUTES

 Over the years 1815-17, a public controversy ensued over who should be given the credit for the invention of the safety lamp.  The controversy involved Davy, George Stephenson, and William Reid Clanny.  UK patent office didn’t start until 1820.  Davy was accused of using ideas from Clanny and George Stephenson’s versions.  Then started a furious dispute over who had actually invented a safety lamp.  Davy & supporters concentrated on the use of gauze for the design, but the dispute then centred on how big was a hole? THE REWARDS

 In October 1817, Davy was rewarded by some of the north-eastern coal owners with an expensive ornamental dinner service, for which £2,500 was raised.  A smaller sum of £1,000 was raised for Stephenson, and in January 1818 he was given a silver tankard, and the remainder of the fund.  But the effect of safety lamps was of great benefit.

 Davy was knighted in 1812, and Baronet in 1818.

A FEW FACTS…

 Colzaline was the official lamp oil, or Solvent40.

 With training and practice, a good Deputy could read a 1.25% methane level and distinguish between 1.25%, 1.5%, 2% onwards.

 At 1.25%, all electricity is to be isolated, all shot firing to be stopped, any diesel engine to be shut down....Also at 2% all men had to be withdrawn to safety.

 Lower point of explosibility is 5%, most dangerous around 10%.

 Methanometers are now mainly used to measure methane.

 “Protector Lamp” have been making miners flame safety lamps in Eccles since 1873. The GR6S Garforth miner’s lamp is the approved method of checking for firedamp in all UK coal mines. Also known as the Eccles Lamp.

 Lamps may still be used, not for presence of methane, but for lack of oxygen. Called “”. i.e. CO2 + nitrogen.

 Like all miners lamps they are based on the principle.

SO HOW BIG WAS A HOLE?

 “There should always be, at least, 24 of those spaces in the length of one inch in every part of the gauze, for this reason, that the flame or blaze will not pass through the wire gauze at or above that fineness.”

 “The gauze of the lamp commonly used contains about twenty six apertures in the length of one inch, or 676 in the square.” DEMO  How did it work?

 “It works because the wire mesh absorbs or takes away the heat of all flame that approaches or comes between them when the flame is divided by a gauze of the above texture but which would not be the case were the distances between the wire greater than specified.”

 But of course, the mesh mustn’t be damaged. THEN AND NOW

Today’s lamp still made in Eccles for blackdamp detection. The colliery lamp room for filling and inspection AND EVEN RECENTLY…

 Lamps were designed for the GPO the forerunner to BT. They were used from the 1960’s to 1998 to test for oxygen deficiency in tunnels and manholes.  Also good for use on boats.  They are still used in the Royal Navy Dockyards for testing bad air in ships holds and on .

And still available parts today DAVY’S LAST WORKS

 He spent the last months of his life writing Consolations in Travel, an immensely popular, somewhat freeform compendium of poetry, thoughts on science and philosophy.

 Published posthumously, the work became a staple of both scientific and family libraries for several decades afterward.

 Davy spent the winter in Rome, hunting in the Campagna on his fiftieth birthday.

 He had wished to be buried where he died, but had also wanted the burial delayed in case he was only comatose.

 He refused to allow a post-mortem for similar reasons. THE RESTING PLACE

 After spending many months attempting to recuperate, Davy died in a hotel room in , , on 29 May 1829 from a second stoke, aged 50. Davy's grave is at Cimetière  Davy's brother tried to secure his Plainpalais in reputation by publishing a biography Geneva and editing his Collected Works.  Today, Davy's brilliance is apparent as an experimentalist, if not as a theorist, and his importance as a Romantic scientist, and a voyager into nature. Images courtesy of the Royal Institution,  He achieved a lot. Lancaster University, Future Learn and Open University.