Platinum group metals Rhodium and palladium Iridium and osmium Wollastonite Names Commentary

William Hyde Wollaston, Smithson Tennant elements

Platinum group metals

• Known as an impurity in silver ore
• by the pre-Columbian people of America,
• the ore of platina was thought to be
• immalleable, and impossible to melt.
• William Hyde Wollaston and Smithson Tennant, however,
• smuggled platinum ore from South America,
• and treated it with aqua regia.
• This dissolved most of it.
• Wollaston investigated the soluble portion,
• which contained platinum, rhodium, and palladium.
• Tennant investigated the insoluble portion, a black powder,
• which contained iridium and osmium.

Rhodium and palladium

• Wollaston dissolved platinum ore in aqua regia
• and added ammonium chloride to remove most of the platinum.
• He added zinc to the filtrate, which precipitated the residual platinum
• along with small amounts of palladium, rhodium, copper, and lead.
• He removed the copper and lead by dissolving the residue in nitric acid,
• and dissolved the rest in more aqua regia.
• He added sodium chloride and evaporated the solution
• to give the rose-red chlorine compound whose color gave it its name.
• After extracting this with hot alcohol,
• he added zinc to precipitate the rhodium.

Iridium and osmium

• After treating platinum ore with aqua regia
• and obtaining an insoluble black powder,
• Tennant heated the powder with sodium hydroxide
• until it was red hot. He cooled the melt
• and dissolved the resulting mass in water
• to obtain a yellow solution with a very pungent smell.
• On acidification the solution gave a white volatile oxide,
• osmium tetroxide, which he distilled from the solution.

Wollastonite

• Wollaston proved that static electricity
• is the same as electricity from a Voltaic pile.
• He contributed to Faraday’s invention
• of the first electric motor.
• He was the first to observe Fraunhofer lines
• in the solar spectrum.
• He invented the camera lucida,
• used as a drawing aid by artists.
• He invented the first lens specifically for a camera
• called a meniscus lens.
• He invented the reflecting goniometer
• to measure the angles of crystals.
• He invented the Wollaston prism
• to separate unpolarized light into polarized components.
• Unrelated to his work, wollastonite and pseudowollastonite,
• useful chain silicate minerals, are named after him.

Names

• Wollaston named rhodium
• after the color of its chlorine compound.
• Wollaston first called palladium ceresium
• after the recently discovered asteroid Ceres,
• but changed his mind named it after the asteroid Pallas.
• Louis Nicolas Vauquelin proposed pténe as a name for osmium,
• from the Greek word for winged,
• but Tennant named osmium because of its ashen and smoky smell
• from the Greek word for smell,
• and he named iridium because of the colors of its compounds
• after the Latin word for rainbow.