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May 16 2012 4 16 /05 /May /2012 18:36

This will be my last elements post. I may be posting less often in the future due to work.

 

I have compiled a list of sources for the elements that are available to the amateur chemist. Bismuth will be discussed here.

 

Bismuth is the left-most metal on the periodic table and the only metal with more than four valence electrons. (All other such elements are nonmetals or semimetals.) Bismuth is a silvery gray metal that develops a pinkish hue on exposure to air due to the formation of an iridescent oxide layer. When bismuth is crystallized from a melt in air, the surface becomes multi-colored due to the formation of this oxide layer. Bismuth is one of the least toxic heavy metals, making it useful for replacing the more toxic lead. Bismuth is quite inert, with an activity slightly above copper. Therefore, it is insoluble in normal acids. Its compounds are prone to hydrolysis in aqueous solution. Bismuth is extremely slightly radioactive; the half-life of the dominant bismuth isotope is over a billion billion years. Its radioactivity was unnoticed until 2003.

 

In element form: Bismuth fishing sinkers and ammunition are relatively common, but expensive. Bismuth crystals are available for sale from mineral shops. Some lead-free solders are made with bismuth alloy.

 

In compound form: Pepto-Bismol contains bismuth subsalicylate.  Some internal deodorants have bismuth subgallate in them. Bismuth oxychloride is used in some cosmetics to obtain a shiny effects.

 

I have several sources of bismuth, but no pictures.

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May 14 2012 2 14 /05 /May /2012 14:52

Copper is a first-row transition metal that produces a wide variety of colors in its compounds and complexes. Copper chemistry is interesting and easy, making it optimal for chemistry beginners. One such exercise involves the creation of every color in the rainbow using copper. In my example below, the only starting copper chemical was copper(II) chloride.

 

Copper-rainbow.JPG

 

Red: Copper metal is reddish. In the photo, I took copper(II) chloride solution and reacted it with zinc metal to produce the reddish copper. I also added some ascorbic acid to the solution after the reaction was completed to absorb dissolved oxygen and prevent the copper from oxidizing to black copper(II) oxide. A red coloration is also obtained through copper(I) oxide. When glucose is heated with Benedict's reagent, red copper(I) oxide is produced. Another copper complex is deep red, and preparation instructions are found here.

 

Orange: Copper(I) oxide has the unique ability of forming a range of colors. The exact coloration depends on the rapidity of the compound's formation. When slowly prepared such as in the above reaction of glucose and Benedict's reagent, copper(I) oxide is red. The orange coloration in the picture was obtained by reacting ascorbic acid with copper(II) chloride to precipitate white copper(I) chloride. Sodium carbonate is added, and the orange compound precipitates.

 

Yellow: Tetrachlorocuprate(II) ion has a yellow coloration. When a small amount of copper(II) chloride is reacted with hydrochloric acid, a yellow solution (in the photo) is formed. Reaction of sodium hydroxide with copper(I) chloride precipitate forms yellow copper(I) oxide.

 

Green: A mixture of blue copper(II) aqua complex and yellow copper(II) chloro complex produces this deep green solution. I made it by dissolving a significant amount of copper(II) chloride in hydrochloric acid. When copper(II) chloride is crystallized from this solution, it is a green solid.

 

Blue: A dilute solution of copper(II) chloride (or sulfate or acetate) in water produces the sky-blue coloration of copper(II) aqua ions. Copper sulfate has a blue coloration when solid.

 

Violet: Tetramminecopper(II) solution is often violet. Copper(II) chloride (or carbonate or sulfate or acetate or oxide, provided  that they are not strongly heated) is dissolved in aqueous ammonia. The precipitate of copper(II) hydroxide dissolves in the ammonia, forming a deep purplish solution of cuprammonium chloride.

 

White: Copper(I) chloride, produced when copper(II) chloride is reacted with ascorbic acid, is white until it gets oxidized by air.

 

Black: When copper(II) chloride is reacted with sodium hydroxide and heated to boiling, the unstable blue copper(II) hydroxide decomposes to black copper(II) oxide in solution, despite being surrounded by water.

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May 14 2012 2 14 /05 /May /2012 12:47

I have compiled a list of sources for the elements that are available to the amateur chemist. Lead will be discussed here.   

 

Lead is a soft blue-gray metal well known for its rather high density, although a significant number of elements exceed the density of lead. Lead is rather inert to many corrosive substances such as hydrochloric and sulfuric acid, but vulnerable to others like acetic acid. Soluble lead compounds are mostly colorless, while the insoluble ones can be either colorless (lead carbonate) or colorful (lead iodide). Lead is one of the few elements that forms insoluble halides. Lead chloride can be dissolved in hot water, while lead bromide is pale white like silver bromide and lead iodide is bright yellow, much brighter than silver iodide. All of them can dissolve to a significant extent in hot water. Lead has a low melting point and is easy to extract and shape, making it the ideal metal for many applications. However, its toxicity is necessitating a replacement of lead by other elements such as bismuth, which are more expensive, less dense, and more brittle. The banning of lead pellets for shooting of birds in wetlands is one such example. Lead forms a sulfide ore that forms large cubic crystals, known as galena. Lead also forms cerussite, which is lead carbonate and was used as a white pigment for many years. Crocoite, lead chromate, is a bright red mineral that was also used as a pigment until it was discontinued.

 

In element form: Lead fishing sinkers, bullets, and wheel weights are still relatively common. Lead acid batteries contain spongy lead metal on the anode. Tin-lead solder can be dissolved in hydrochloric acid, leaving lead behind.

 

In compound form: Lead white pigment contains lead carbonate. Lead glass contains lead silicate. Lead acid batteries have lead dioxide cathodes. Piezocrystals can have lead titanate or lead zirconate titanate in them.

 

Here is my sample of lead. It is a wheel weight containing about 95% lead.

 

Wheel weight

 

 

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May 12 2012 7 12 /05 /May /2012 12:49

Thallium is a highly toxic element which had its primary household source (thallium sulfate in rat poison) banned in the 1970s due to its extreme toxicity. Thallium minerals can be obtained, as well as thallium metal, but both are rare and highly expensive. Back when mercury thermometers were legal, thallium was added as an 8% alloy to lower the freezing point, making the thermometer more useful in cold conditions.

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May 10 2012 5 10 /05 /May /2012 12:52

I have compiled a list of sources for the elements that are available to the amateur chemist. Mercury will be discussed here.  

 

Mercury is one of the two liquid elements on the periodic table and the only metal that is liquid. Well known for its toxicity and interesting properties, mercury is a fascinating element to experiment with. Mercury itself is a mobile (easily flows), silvery gray, and dense metal. Under certain conditions, it may form a skin of orange mercury(II) oxide, although my mercury has never done this. Mercury forms alloys with many elements known as amalgams. Mercury is found in the ore cinnabar, which consists of red mercury(II) sulfide. When it is roasted in air, it forms mercury vapor, which can be condensed to form pure metallic mercury. Sometimes cinnabar is oxidized by air, forming droplets of native mercury, which are the only liquid mineral. Mercury is a rather inert metal, but it dissolves in oxidizing acids to produce various colorless mercury salts. Mercury(II) chloride, the most common source of mercury ions, is a colorless, highly toxic, and water-soluble solid. Most insoluble mercury compounds are brightly colored.

 

In element form: Old tilt switches contain beads of mercury metal. These can be found in old thermometers, barometers, and blood pressure sensors. Mercury vapor bulbs have mercury vapor and sometimes mercury metal in them. Fever thermometers used to contain mercury metal. Dental amalgams contain 50% mercury. Fluorescent bulbs contain tiny amounts (5 milligrams or so) of mercury vapor. High pressure sodium bulbs have sodium amalgam in them.

 

In compound form: Cinnabar is made of mercury sulfide.

 

Mercury-bead.JPG

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May 9 2012 4 09 /05 /May /2012 12:38

I have compiled a list of sources for the elements that are available to the amateur chemist. Gold will be discussed here. 

 

Gold, the most well known precious metal, has been that way since antiquity. Gold is a yellow, malleable, dense (19 g/cm3 compared to about 11 for lead), and soft metal. It is sometimes found in the earth in nugget form. Although nuggets are becoming increasingly rare, a few are still found. More often, gold is scattered in tiny specks throughout quartz rock. There are several ways to extract this gold. One is to grind the rock to powder and place it in mercury. The gold and silver dissolve, forming amalgams, while the common dirt does not dissolve. The mercury is evaporated and recondensed to create "electrum", from which the gold and silver are separated. Another method is the cyanide process, where air is bubbled through a sodium cyanide bath with powdered gold ore submerged in it. The gold dissolves easily in this mixture due to complex formation with the cyanide ion. The solution is treated to obtain the pure gold. Gold metal itself is resistant to attack by most acids. However, a few acids, such as aqua regia and selenic acid, have the ability to dissolve gold. Gold easily alloys with other elements.

 

In element form: Gold jewelry or gold-plated jewelry is common. Gold-plated electrical contacts are also common. Gold bullion bars are available for sale from gold dealers.

 

In compound form: No sources found.

 

Here are my samples of gold. One is a piece of gold foil generously donated by my dentist upon request, along with a piece of lead foil. The other is a squashed piece of a gold plated electrical contact from a headphone jack.

 

Gold.JPG

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May 8 2012 3 08 /05 /May /2012 18:32

Note: Unfortunately, there are no photographs in this document. I have, can produce, or can obtain the pictures of a large number of compounds, but posting hundreds of pictures in one post is difficult because of size restrictions on the hosting site. Instead, there are links to pictures. While most of these link to a JPEG file, there is no guarantee that all of these links are safe. Most are.

 

The elements on the periodic table form simple inorganic compounds with a wide range of color. Nowhere is this more evident than with the transition metals, although most elements have their own uniquely colorful compounds.

 

Below is a list of elements with a few of the colorful substances pertaining to each element. Radioactive elements such as plutonium and uranium are not included. This list makes no claim of completion; many elements have dozens of inorganic and organometallic complexes with vastly different colors and properties which are not mentioned here at all.

 

Alkali metals: The alkali metal compounds have no visible color from the metal. Other ions may contribute their coloration to a compound.

 

Alkaline earth metals: The alkaline earth metal compounds have no visible color from the metal. Other ions may contribute their coloration to a compound.

 

Aluminium, boron, gallium, and indium: None of these elements form any colored compounds when pure. Aluminium chloride is often colored slightly yellow.

 

Antimony: antimony trisulfide – dark gray or yellow, hexachloroantimony(V) acid – greenish, antimony(III) bromide – colorless solid and yellow liquid, antimony(III) iodide – red, ammonium antimony(IV) bromide – black, antimony(V) oxide – pale yellow, sodium thioantimonate(V) – yellow

 

Argon: See “Noble gases”.

 

Arsenic: arsenic – yellow or gray, arsenic(III) iodide – red, arsenic(II) iodide – red, realgar – red, arsenic(V) sulfide – yellow

 

Barium: See “Alkaline earth metals”.

 

Beryllium: See “Alkaline earth metals”.

 

Bismuth: bismuth(II) chloride – black, bismuth(III) bromide – yellow orange, bismuth(III) iodide – black, tetraiodobismuthate(III) - red orange, bismuth(III) oxide iodide – red, bismuth(III) oxide nitrite – light yellow, bismuth(III) oxide – light yellow, sodium bismuthate – light brown, bismuth(V) oxide – red, bismuth(III,V) oxide – brown

 

Boron: See “Aluminium, boron, gallium, and indium”. Boron - gray crystals or red brown powder.

 

Bromine: bromine – dark red liquid, cesium dichlorobromide – yellow, sodium hypobromite – yellow, bromine nitrate – pale yellow

 

Cadmium: cadmium sulfide – yellow, cadmium selenide – red, cadmium(II) oxide – white or brown

 

Caesium: See “Alkali metals”. Caesium forms many colorful complexes with halogens which are mentioned under each specific halogen.

 

Calcium: See “Alkaline earth metals”.

 

Carbon: Metal carbides often have a gray or blackish coloration. potassium carbide – copper colored or bluish gray, tricarbon disulfide – bright red liquid, carbon diselenide – bright yellow liquid

 

Cerium: Cerium dioxide - light yellowish. Cerium(IV) sulfate – bright yellow orange, cerium(IV) fluoride – brown powder, cerium(IV) ammonium nitrate – red

 

Chlorine: Chlorine - light yellow green, Sodium hypochlorite - light green in solution, chlorine dioxide -bright yellow green gas, dichlorine monoxide - brown gas, dichlorine hexoxide - red liquid

 

Chromium: chromium(II) chloride solution - blue, chromium(II) fluoride – dark green, chromium(II) iodide – brown, chromium(III) chloride – purple anhydrous and green hexahydrate with purplish gray or greenish gray or grayish solution, chromyl fluoride – red brown gas, chromyl chloride - red liquid, chromium(IV) fluoride – brown with blue vapor, chromium(III) oxide – blue green solid, alkali metal chromates – bright yellow, dichromates – orange, trichromates – red (left one in picture), chromium(VI) oxide – reddish purple, chromium(III) phosphate – grayish brown, chromium(II) acetate – dark red brown, chromium(III) acetate – purple blue

 

Cobalt: cobalt(II) chloride - blue anhydrous and pink hexahydrate, cobalt(II) ammine complex – tan, cobalt(II) bromide - green anhydrous and pink hexahydrate, cobalt(II) iodide - black or yellow anhydrous and pink hexahydrate, cobalt(II) oxide - olive green, cobalt(II,III) oxide – black, cobalt(II) hydroxide - red or blue, cobalt(III) sulfate – green, sodium cobaltinitrite – yellow, cobalt(II) carbonate - indigo, cobalt(II) phosphate – purple, cobalt borate – tan, cobalt chloro complex - violet to greenish-blue, cobalt(III) ammine - orange or purple

 

Copper: copper – pinkish red, copper(I) oxide - yellow or red, copper(II) oxide – black, copper(II) carbonate – green blue, copper chloro complex – green to yellow, caesium copper(II) chloride – red orange, copper(II) chloride – brown when anhydrous and green or blue hydrate, copper(II) bromo complex – brownish or purplish, copper(II) bromide – black, copper(II) hydroxide – blue solid, copper(II) sulfate – gray anhydrous and blue pentahydrate, copper(I) acetylide – brown, copper(II) ammine complex – deep blue, copper(III) periodate complex - dark red

 

Dysprosium: dysprosium(III) chloride – yellow, dysprosium(III) nitrate – pale yellow

 

Erbium: erbium(III) oxide – pink, erbium(III) chloride – pink, erbium solutions - yellow

 

Europium: europium(III) oxide – pale pink, europium(III) carbonate - yellow, europium(III) chloride – yellow, europium(III) sulfate – pale pink

 

Fluorine: fluorine – brownish gas

 

Gadolinium: See “Rare earth metals”.

 

Gallium: See “Aluminium, boron, gallium, and indium”.

 

Germanium: germanium(II) oxide – yellow or brown, germanium(IV) iodide – orange red, germanium(II) iodide – yellow

 

Gold: gold – golden yellow, gold(I) chloride – yellow, gold(III) chloride – ruby red solid and yellow solution, potassium gold(III) chloride – light yellow, gold(III) oxide – black or brown, gold(I) sulfide – brown, gold(III) sulfide – black,  gold(I) cyanide – yellow

 

Hafnium: hafnium(IV) iodide – red

 

Helium: See “Noble gases”.

 

Holmium: holmium(III) oxide – pale yellow or pink, holmium(III) chloride – yellow or pink

 

Indium: See “Aluminium, boron, gallium, and indium”.

 

Iodine: iodine – blue black crystals and purple vapor, iodine monochloride – brown liquid, iodine trichloride – orange or yellow, triiodide solution – dark brown, potassium dichloroiodide – orange, dibromoiodide – red, tetrachloroiodide – golden yellow, iodine(III) nitrate – yellow, diiodine tetroxide – yellow, cationic iodine - blue green

 

Iridium: iridium(IV) oxide – blue black, iridium(III) oxide – pale green, iridium(III) chloride – green, potassium iridium(IV) chloride – olive green, iridium(IV) chloride - purple or tan or green, tetrachloroiridate(IV) - deep red

 

Iron: iron(I) nitrosyl - green brown solution, iron(III) chloride – yellow brown solutions and solid, iron(II) chloride – yellow green solution, green hydrate, iron(III) bromide – black, ferrates in solution - light magenta, iron(II) hydroxide - white to greenish gray, iron(II,III) oxide - black, iron(III) oxide - red orange or brown, basic iron(III) acetate - red, ferric nitrate - light purplish, iron(III) ammonium sulfate – yellowish or purplish, Prussian blue – blue, ferricyanic acid - yellow or brown solution, potassium ferricyanide - red, tetrachloroferrate(III) - yellow, potassium ferrocyanide - light yellow

 

Krypton: See “Noble gases”.

 

Lanthanum: See “Rare earth metals”.

 

Lead: lead(II) oxide – light yellow or red, lead(II,IV) oxide – bright red, lead(IV) oxide – dark brown, lead(IV) chloride – yellow, ammonium lead(IV) chloride – yellow, potassium lead(II) iodide – light yellow, sodium metaplumbate or orthoplumbate – yellow, lead(II) sulfide – gray , lead(IV) sulfate – white or yellow green, lead(II) iodide – bright yellow to red, lead(II) chromate – bright yellow

 

Lithium: See “Alkali metals”.

 

Lutetium: See “Rare earth metals”.

 

Magnesium: See “Alkaline earth metals”.

 

Manganese: permanganate solutions - magenta, solid permanganates - dark purple, manganate(VI) solutions - green, manganate(V) – blue, manganese(III) chloro complex - brownish, manganese(II) chloride - light pink, manganese dioxide - black, manganese(II) hydroxide – light tan, manganese heptoxide - greenish or reddish oil, manganese(III) sulfate - dark green, caesium manganese(III) sulfate – red, manganese(III) acetate – brown 

 

Mercury: mercury(II) oxychloride – brown, potassium mercury(II) iodide – light yellow, copper(I) mercury(II) iodide – red or brown, mercury(II) sulfide – red or black, mercury(II) selenide – gray, mercury(II) iodide – red or yellow, mercury(II) oxide – orange

 

Molybdenum: molybdenum blue – blue or olive, molybdenum(II) chloride – yellow, molybdenum(III) chloride – red brown, molybdenum(III) hydroxide - greenish gray, molybdenum(V) chloride – blue black, molybdenum(III) bromide – black, potassium molybdenum(III) chloride – red, molybdenum(IV) oxide – brown or violet, Mo4O11 – violet, molybdenum(VI) oxide – white or bluish when cool and yellow when heated, molybdic acid – yellow crystals, molybdenum(IV) sulfide – blue gray, ammonium molybdenum(V) oxychloride – green, zinc molybdenum peroxo complex – red brown, molybdenum(VI) peroxo complex - yellow

 

Neodymium: neodymium(III) oxide – sky blue or pink or purple, neodymium(III) fluoride – lilac, neodymium(III) chloride solutions – rose pink or almost colorless, neodymium(III) bromide – green solid and dark brown liquid

 

Neon: See “Noble gases”.

 

Nickel: nickel – golden tinged gray, nickel(II) aqua solutions - green, nickel(II) chloro complex – yellow, nickel(II) ammine complex – blue, nickel(II) chloride – yellow green anhydrous and blue green hexahydrate, nickel(II) iodide - black anhydrous and blue green hydrate, nickel(II) oxide - green, nickel(III) oxide – black, nickel(II) thiocyanate – brown, potassium nickel(II) cyanide - orange

 

Niobium: niobium(V) chloride – yellow, niobium(II) chloride – brown, niobium(III) chloride – green black, niobium(IV) chloride – brown black, niobium(V) bromide – red, niobium(IV) iodide – dark gray, niobium(II) iodide – gray black, niobium(V) oxide – white when cool and yellow when heated, niobium(V) peroxo complex - yellow

 

Nitrogen: nitrogen dioxide – brown gas, nitric oxide –colorless gas and blue liquid, dinitrogen trioxide – blue liquid, nitrogen triiodide – dark brown powder, nitrosyl chloride – orange gas, lithium nitride – ruby red

 

Noble gases: The noble gases are colorless.

 

Osmium: osmium(IV) chloride – red brown or black, ammonium osmium(IV) chloride – dark red, osmium(IV) oxide – black, potassium osmate(VI) – pale violet red

 

Oxygen: dioxygen difluoride – brown gas, red liquid, ozone – light bluish gas, hydrogen peroxide- very pale bluish liquid, lithium and sodium peroxides - yellowish

 

Palladium: palladium(II) chloride – red brown solid and brown solution, palladium(II) oxide – black, potassium palladium(II) chloride – dark yellow or brown, ammonium palladium(II) chloride – olive green, palladium(IV) chloride complex – bright red, potassium palladium(IV) chloride - orange, palladium(II) ammine complexes – red or yellow, palladium(IV) oxide - dark red

 

Phosphorus: phosphorus – yellowish, red brown, or violet, diphosphorus tetraiodide – red, phosphorus trisulfide - yellow brown, phosphorus triselenide - orange, phosphorus pentabromide - yellow

 

Platinum: platinum(IV) chloride – reddish brown, platinum(III) chloride – dark green, platinum(II) chloride – greenish brown, chloroplatinic(IV) acid – orange, chloroplatinic(II) acid solution – red, potassium platinum(IV) chloride – yellow, potassium platinum(II) chloride – red, platinum(II) oxide – black, platinum(IV) oxide – yellow, potassium platinum(II) cyanide – blue or yellow, platinum(II) ammine complex – dark colored or yellow

 

Potassium: See “Alkali metals”.

 

Praseodymium: Praseodymium(III) chloride – bluish green when anhydrous and green when heptahydrated, praseodymium(III) fluoride – green, praseodymium(IV) oxide - black (top center), praseodymium(III) oxide - light green

 

Rare earth metals: Lanthanum, yttrium, lutetium, gadolinium, and ytterbium have no visible color in the majority of their compounds.

 

Rhenium: rhenium(III) chloride – red purple, rhenium(V) chloride – black brown, rhenium(IV) chloride complex – yellow green, rhenium(VI) oxychloride – red brown, rhenium(IV) oxide – gray black, rhenium(VI) oxide – red, rhenium(VII) oxide – bright yellow, sodium rhenite(IV) – brown, barium rhenate(VI) – green, rhenium(IV) sulfide – black, rhenium(VII) sulfide – black

 

Rhodium: rhodium(III) chloride – yellow HCl solution or red solid, rhodium(III) oxide – lemon yellow, rhodium(III) sulfate – red or yellow , rhodium(II) sulfate - red

 

Rubidium: See “Alkali metals”.

 

Ruthenium: ruthenium(IV) oxychloride – dark brown, ruthenium(III) chloride – yellow brown solution, ruthenium(IV) oxide – dark gray, ruthenium(IV) chloride complex – orange brown, ruthenium(VIII) oxide – yellow solid or solution and orange liquid,  ruthenate - red, potassium perruthenate – black solid and green solution, ruthenium(II) - lavender

 

Samarium: samarium(III) oxide – light yellow, samarium(III) sulfate – yellow, samarium(III) iodide – orange, samarium(II) iodide – yellow with brown solution

 

Scandium: Scandium iodide – yellow (in light bulb core), scandium sulfide – yellow

 

Selenium: selenium – red or purplish gray or black, diselenium dichloride – dark red  liquid, selenium tetrachloride – faint yellow, ammonium selenium chloride – yellow, diselenium dibromide – black liquid, selenium tetrabromide – yellow, selenium oxychloride – yellow liquid, selenium sulfur trioxide – dark green, selenium nitride – orange

 

Silicon: Silicon – bluish, silicon tetraiodide - yellow liquid, colorless solid

 

Silver: silver(I) oxide – dark brown, silver(I) carbonate – light yellowish, silver(I) iodide – light yellowish, silver(I) sulfide – black, silver(II) oxide – grayish, sodium argentite – light green, silver nitride – black

 

Sodium: See “Alkali metals”.

 

Strontium: See “Alkaline earth metals”.

 

Sulfur: Sulfur - yellow solid and red when molten, sulfur dichloride – red liquid, disulfur dibromide - red liquid, disulfur dichloride - yellow liquid, disulfur trioxide – greenish, thionyl bromide - yellow liquid, sulfur nitrides – yellow orange. Alkali metal sulfides turn yellow upon exposure to air.

 

Tantalum: tantalum(IV) chloride – brown, tantalum(IV)  bromide – black, tantalum(V) bromide – yellow, tantalum(V) iodide – black

 

Tellurium: potassium telluride – pale yellow, chlorotellurate(IV) and bromotellurate(IV) - orange or yellow, iodotellurate(IV) – gray, tellurium(VI) oxide – yellow or gray, tellurium sulfur trioxide – brown

 

Terbium: Tb4O7 – dark brown, terbium solutions – pale pink

 

Thallium: thallium(I) fluoride – yellow, thallium(I) bromide – pale yellow green, thallium(I) iodide – yellow or red, thallium(III) bromide – light yellow, rubidium thallium(III) bromide – yellow, thallium(I) triiodide – black, thallium(I) oxide – black, thallium(I) hydroxide – yellow, thallium(III) oxide – black, thallium(I) sulfide – black

 

Thulium: thulium(III) chloride – green, thulium(III) oxide - green

 

Tin: tin(II) iodide – orange, tin(IV) iodide – orange, tin(II) oxide – black, tin(II) bromide – bright yellow, tin(II) sulfide – brown, tin(IV) sulfide – gold yellow

 

Titanium: Titanium peroxo complex – orange, titanium(II) halides – black, titanium(III) chloride – violet, titanium(III) bromide – bluish black, titanium(III) iodide – violet, titanium tetrabromide – yellow orange, titanium disulfide – yellow, titanium nitride - yellow brown, titanium(III) hydroxide - dark blue, titanium(III) fluoro complex - green

 

Tungsten: tungsten(V) chloride – black, tungsten(VI) chloride – blue black, tungsten(IV) oxide – brown, W18O49 – red or violet, tungsten blue – brown to blue to violet, tungsten(VI) oxide – yellow, tungsten oxytetrachloride – red, tungsten sulfide – blue gray, potassium tungsten(III) chloride – dark green

 

Vanadium: vanadium(II) solution – lavender, vanadium(II) hydroxide - black, vanadium(III) solution – light green blue, vanadium(III) hydroxide - green gray, vanadium(IV) hydroxide - gray, vanadate(IV) solution - red brown, vanadium(IV) chloride – reddish liquid, vanadium(II) bromide – reddish brown, vanadium(II) sulfate – reddish brown, vanadium(III) bromide – black with violet vapor, vanadium(II) iodide – violet, vanadium(III) iodide – brown, vanadium oxychlorides – brown or green or yellowish or orange, vanadyl sulfate – bright blue, vanadates – light yellow, vanadium(V) oxide – orange brown, vanadium(V) peroxo complex - yellow and purple

 

Xenon: See “Noble gases”. Some xenon compounds may be colorful.

 

Ytterbium: See “Rare earth metals”.

 

Yttrium: See “Rare earth metals”.

 

Zinc: zinc oxide – white when cold and yellow when strongly heated

 

Zirconium: zirconium tetraiodide – red brown

 

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May 8 2012 3 08 /05 /May /2012 12:57

I have compiled a list of sources for the elements that are available to the amateur chemist. Platinum will be discussed here.

 

Platinum is a dense, shiny, expensive metal. It is extremely malleable, just like gold, allowing it to be shaped easily. Platinum is quite corrosion resistant as well, making it very useful in chemistry. It only dissolves in aqua regia, not in any other acid. It is attacked by halogens and molten salts though when heated. Platinum forms divalent and tetravalent compounds, both of which are oxidizing and colorful. Platinum sponge is a finely divided form of platinum that is used as a catalyst. It is created by the heating of ammonium platinum(IV) chloride. Platinum is not affected by oxygen at any temperature, making it useful for high temperature work. Platinum was found in ores brought to Spain from the New World. It is often found along with similar precious metals: osmium, iridium, ruthenium, rhodium, and palladium.

 

In element form: Platinum spark plugs and platinum jewelry are relatively common. Some platinum spark plugs have a center wire of pure platinum, while others have a wide platinum-plated electrode.

 

In compound form: No sources found.

 

Here is my sample of platinum. It is a couple of spark plugs. The left has a platinum wire, the right has a platinum-iridium alloy plating on the center electrode.

 

Platinum.JPG

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May 7 2012 2 07 /05 /May /2012 12:51

I have compiled a list of sources for the elements that are available to the amateur chemist. Iridium will be discussed here.

 

Iridium is one of the rarest and densest elements in the earth's crust. It is found in small concentrations in platinum ores and competes with osmium for position of densest element, the two's densities being extremely close (22.56 grams per cubic centimeter for iridium, compared with 22.59 for osmium). Iridium's is named after the "goddess of the rainbow" because of the many colors that it exhibits in its salts. Meteorites tend to contain larger quantities of iridium than the general earth. Iridium does not dissolve in any acids, but is attacked by halogens and some molten salts when heated to a high temperature. Iridium black is an extremely black pigment for ceramics made of finely divided iridium metal. See this link for more information about the colorfulness of iridium chloride and its complexes.

 

In element form: Iridium spark plugs often contain pure iridium or iridium-platinum alloys plated on the central electrodes. Osmiridium pen tips for expensive pens contain iridium metal.

 

In compound form: No sources found.

 

Here is my sample of iridium. It is a spark plug with the electrode coated with a platinum-iridium alloy (90% Pt 10% Ir is typical).

 

 

Iridium.JPG

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Published by LanthanumK - in Elements
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May 6 2012 1 06 /05 /May /2012 03:04

 

Hydrolysis is the reaction of a compound or ion with water. Most hydrolysis reactions in inorganic chemistry result in the donation or removal of a proton by water, forming either hydroxide or hydronium ions. Two sample hydrolysis reactions are:

NH4(+) + H2O à NH3 + H3O(+) forms an acidic solution

 

CN(-) + H2O à HCN + OH(-) forms an alkaline solution

Here, ammonium ion reacts with water, generating ammonia and hydronium, which makes an acidic solution. Below, cyanide ion reacts with water as well, generating hydrogen cyanide and hydroxide. Learn more by taking a General Chemistry II course.

These reactions happen with salts of weak acids or weak bases, which is what gives the salts their pH. Many other chemical compounds form their unique hydrolysis products which can be interesting. Most metal oxides are weak bases, making their salts prone to hydrolysis. The less basic the oxide is, the stronger the hydrolysis of the salt and the more acidic the resulting solution. Below several metal and semimetal ions are listed, along with their hydrolysis properties and any uses of such properties.

 

Aluminium: Aluminium forms a stable complex with water, but solutions of aluminium with strong acids are highly acidic, showing the weakness of aluminium(III) hydroxide as a base.

 

Antimony(III) and arsenic: This ion is stable in strongly acidic solutions. When diluted with water, it produces a white precipitate of antimony oxychloride in a similar manner to bismuth. However, the hydrolysis happens at an even lower pH. Arsenic(III) hydrolyzes even more easily than antimony(III) in water. Arsenic pentoxide, however, is insoluble in concentrated hydrochloric acid, preferring instead to dissolve in water, forming its own acidic solution. When the nonmetals are reached, the oxides no longer keep up any pretense of basicity.

 

Bismuth(III): When a colorless acidic (pH 1 or so) solution is bismuth(III) chloride is diluted with water, a white precipitate of bismuth oxychloride is instantly formed, even though the pH remains around 2. Bismuth(III) oxide is a very weak base and so its salts are highly acidic and prone to hydrolysis. This is how bismuth oxychloride, a substance used in cosmetics, is created.

 

Monovalent ions: Monovalent ions hardly even have an acidic pH in most cases, showing that they do not hydrolyze at all. The alkali metal salts with strong acids are completely neutral. Other monovalent ions (thallium, silver, copper) can have different properties because of their greater proximity to the right side of the periodic table, but none are easily hydrolyzed AFAIK.

 

Most divalent ions:  Copper shows a very small tendency toward hydrolysis. The production of an acidic pH of 3 and higher is the most hydrolysis that occurs. Therefore, aqueous solutions of metals which form divalent ions (cobalt, copper, manganese, iron, nickel, zinc, cadmium, mercury, lead, alkaline earth metals) are often the easiest to study in amateur chemistry due to ease of dissolution in water.

 

Niobium(V): Niobium pentachloride is a yellow solid that hydrolyzes completely in water and in moist air. Even in the most acidic solutions it slowly hydrolyzes, depositing white niobium pentoxide.

 

Phosphorus: Although not technically an ion, simple phosphorus compounds are highly prone to hydrolysis. Phosphorus trichloride, a colorless liquid, fumes upon contact with water, forming phosphorous acid and hydrochloric acid. Phosphorus pentachloride also has a vigorous reaction. The reaction between phosphorus triiodide and water (which creates hydriodic acid) is used in illegal drug manufacture.

 

Silicon compounds: Silicon tetrachloride, a typical binary silicon compound, hydrolyzes rapidly with water, releasing silicic acid (hydrated sand, essentially) as a colorless gel along with hydrogen chloride fumes. Because of silicon tetrachloride's unique properties, it is used to produce high-purity silica gel by mixing with water.

 

Sulfuryl chloride: This compound hydrolyzes much more slowly in water. I have heard that it can take weeks for a layer of sulfuryl chloride to completely react with water.

 

Thionyl chloride: This compound reacts vigorously with water, releasing sulfur dioxide gas and hydrogen chloride fumes in large amounts, as I accidentally experienced upon opening a lithium battery containing the substance. The high acidity of this complex is used to prevent sensitive metal chlorides (e.g. rare earth chlorides) from hydrolyzing as they are dehydrated. The thionyl chloride reacts with any released water, releasing a cloud of acidic gases that keep the anhydrous chloride stable.

 

Tin(II): A solution of tin(II) chloride is stable in hydrochloric acid, but slowly hydrolyzes when diluted, forming a white precipitate of tin(II) oxychloride. This is not desired in most circumstances, and is prevented by using hydrochloric acid.

 

Tin(IV): Solutions of tin tetrachloride in water are generally turbid to some degree. Because tin dioxide is a weak base, the solution hydrolyzes easily, forming white insoluble tin dioxide. The anhydrous form of tin tetrachloride fumes upon contact with air or water. This was used in the past as a naval smokescreen.

 

Titanium(IV): Titanium tetrachloride, one of the common tetravalent titanium compounds, hydrolyzes very strongly. When the anhydrous compound is sprayed into air, it forms a dense white smoke as a result of reacting with the water vapor in the air. This is used to determine air flow in a room or to test smoke detectors for effectiveness.

 

 

 

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