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Martinus Van Marum (1750-1837) "discovers" a light blue gas,
with the help of Mr. Cuthbertson

Ozone, which liquifies as an explosive indigo-blue liquid & solidifies as violet crystals,
was produced in prodigious quantities by a huge 18th century high-voltage generator

Van Marum`s Frictional Electrostatic Machine 1785
~ large drawing of a tandem set-up ~
Marum`s Electrostatic Generator, set up for positive with respect to ground
Marum`s Electrostatic Generator, set up for negative with respect to ground
positive output
negative output

Dutch experimentalist Martinus van Marum (1750-1837) was extremely interested in electricity. He hired English instrument maker John Cuthbertson (1743-1821) to construct a giant double plate-glass frictional electrostatic generator. Cuthbertson had constructed various glass disc electrical machines with diameters from 2 to 7 feet in 1783, but the monster he built in 1785 at Haarlem, Netherlands, was designed for performance --

The voltage developed, almost three quarters of a million volts, was easily capable of overwhelming and arcing over the leyden jars. Controlled discharges from the leyden battery were of formidable energy --

During the operation of the machine, spectacular effects were produced - "Persons within 10 feet of the plates experienced a sort of creeping sensation over them, as if surrounded by a spiders web." and, "..a thread became attracted at a distance of 38 feet."

The stench of ozone gas was most apparent during operation of the huge machine. This is not surprising, considering the high electrostatic fields, ".. a pointed wire exhibited the appearance of a luminous star at a distance of 28 feet from the conductor."

Martinus Van Marum (1750-1837)
Marum noted, "the odor of electrical matter," determined that air or oxygen, subjected to electrical discharge, tarnished mercury, but he did not identify the gas as an allotrope of oxygen.

Read more about the Van Marum generator in Snow-Harris` 1853 section on The Plate Glass Electrical Machine, and more on it`s Leyden Battery See a replica of the machine at Teylers Museum, Haarlem, Netherlands. off-site link

The Preparation & Properties of Ozone

3O2 = 2O3

Marum`s electrostatic generator produced ozone in low concentrations, so he was unaware that a beautiful blue gas was being evolved - the colour becoming apparent only when pure. The gas remained un-named for 55 years, until in 1840, C.F. Schonbein detected the same peculiar odour in the oxygen liberated during the electrolysis of acidulated water, and gave it the name -

(from the Greek Greek for `to smell.` ozein, to smell).

The passage of a high voltage, alternating electric discharge through a gas stream containing oxygen will result in the breakdown of the molecular oxygen, to atomic oxygen. Some of the atoms of oxygen thus liberated can reform into ozone, while others simply recombine to again form oxygen.

Siemens`s Ozoniser - 1858

In 1857 Werner Von Siemens designed the ozone generator above, consisting of two concentric glass tubes. The inner tube has a tin-foil coating on its inner surface, the outer tube is similarly coated on its outer surface.

The Preparation of Ozone - page 220 Modern Inorganic Chemistry, Mellor 1934

The electrical discharge must be a "corona" or silent discharge - sparks destroy ozone. The apparatus above consists --

A - terminal connected to the inner surface
B - terminal connected to outer surface
C - gasholder
D - calcium chloride drying tube
E - battery
G - induction coil

Brodie`s Ozoniser 1872

Oxygen passes slowly through the annular space between two glass tubes, the inner tube filled with dilute copper sulphate solution, and the whole apparatus placed in a jar of the same liquid. Wires from an induction coil dip into the liquids. A bluish-violet glow is seen on the glass surfaces, accompanied by a hissing noise.

Brodie`s Ozone Generator - Page 285 Inorganic Chemistry, Partington 1946

Other Methods of Ozone Production

Ozone, chemically, is the triatomic, allotropic form of oxygen having the chemical symbol O3 and a molecular weight of 47.9982. These three oxygen atoms form a relatively unstable, highly oxidative molecule that serves as a strong oxidant for many commercial and industrial applications. The gas condenses to an indigo blue liquid which is extremely explosive -

Mellor, 1934 - "... a deep indigo blue liquid is obtained which is opaque in layers 2mm thick..... the liquid is particularly liable to explode when it reaches minus 120 o"

The Properties of Ozone. Page 291 Inorganic Chemistry, Partington 1946

Effect on Quicksilver.   Marum noted that the gas evolved from his great machine tarnished mercury metal. The effect is more remarkable than that. The distinct meniscus displayed by quicksilver is destroyed, and the metal adheres to glass. Upon shaking with water, the mercury recovers its original form. H.B. Baker determined the reaction is due to oxidation to Hg2O, which dissolves in mercury.

Soret`s apparatus for the determination of the density of ozone

Harries` Hyperozone
O4   tetraoxygen   O4

The 1929 Encyclopaedia Brittanica mentions another oxygen allotrope, oxozone, under ozone -

"The least volatile portions of liquid ozone contain a denser gas of great chemical activity to which the name oxozone has been given with a molecular formula O4 (C.D. Harries, 1911)"

Also, under ozonides -

"...remarkable results subsequently obtained by C.D. Harries (1905 -15) by passing ozonized oxygen into solutions of unsaturated organic compounds in inert solvents.... ...In certain instances unsaturated organic compounds take up O4 at the double linkage. The products are termed oxozonides, and are regarded as being due to the presence of oxozone, O4, in ozonized oxygen. Propylene gives C3H6O4 and butylene forms both ozonide, C4H8O3, and oxozonide, C4H8O4"

Mellor, 1934 - "There is some evidence indicating the formation of an even more condensed form of oxygen than ozone when the latter is produced by a silent electrical discharge of very high voltage - 18,000 volts. The last fractions of the fractional distillation of the liquefied product furnished Harries with a hyperozone, but it has not been isolated"   Modern Inorganic Chemistry p228

The exceedingly dangerous work of C.D. Harries appears to have been forgotten, according to this reference to the discovery of tetraoxygen in 2001- nature, offsite link

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