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April 27 2012 6 27 /04 /April /2012 13:11

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

 

Holmium is one of the less reactive rare earth metals. It forms a yellow trivalent solution when dissolved in acids. Holmium(III) oxide has a color that changes depending on the light source. In normal light it is a dull yellow, while in trichromatic light it is bright pink.

 

In element form: No sources found.

 

In compound form: Commercial calibrators for spectrophotometers use holmium oxide glass or in some cases a holmium oxide solution.

 

I do not have any holmium or holmium compounds at the time of this writing.

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April 26 2012 5 26 /04 /April /2012 13:09

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

 

Dysprosium is one of the less reactive rare earth metals. Its compounds are trivalent and generally colorless, although the soluble compounds supposedly have a yellow solution. Dysprosium is quite a boring rare earth metal.

 

In element form: Dysprosium alloys are used on many hard disk platters. Terfenol-D, the alloy in a Soundbug(r), contains dysprosium metal.

 

In compound form: No sources found.

 

Here is my sample of dysprosium. It is a hard disk platter.

 

Dysprosium.jpg

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April 25 2012 4 25 /04 /April /2012 15:46

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

 

Terbium is one of the less reactive rare earth metals. It forms trivalent compounds, white and boring. Terbium also forms some divalent and tetravalent compounds, such as terbium (III,IV) oxide, which is black. Terbium compounds fluoresce green brightly. Higher valent terbium compounds are strong oxidizing agents.

 

In element form: Terfenol-D, an alloy used in Soundbug(r) speakers, contains terbium, dysprosium, and iron.

 

In compound form: CFL bulbs and CRT tubes contain green phosphors, most commonly made using terbium doped yttrium oxide or some other terbium doped compound.

 

Here is my sample of terbium. It is a CFL bulb.

 

Fluorescent lamp

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April 24 2012 3 24 /04 /April /2012 13:20
    At my college, I had a poster session where individuals are asked to create posters of some research project or work that they did and present them. I decided to create my poster about titanium anodizing. Since the time when I discovered the range of colors obtainable with titanium when it is anodized, I was fascinated by the process. Therefore, I decided to use the entire range of voltages to create the complete anodizing spectrum.
 
I ran into some electrical problems, however. I could only get a top voltage of 63 volts with nine volt batteries, so I decided to ask my neighbor to loan me his variable transformer. After a couple of fuse blowings from incorrectly connected wires (the strands of the wire were spread out and making undesirable electrical connections), he soldered the wires to the bridge rectifier that I was using. But there were more problems.
 
I remember learning about RMS voltage and how that 120 volts is not really 120 volts. But I did not realize this at the time so I believed that "70 volts" as marked on the AC voltage side would translate to a peak of 70 volts on the DC side. However, this was only the average; the peak voltage was somewhere around 110 volts, as evidenced by the anodizing color. After several unsuccessful attempts, we placed a motor starter capacitor in series to level out the voltage. It worked much better after that. Read about root mean square on Wikipedia for more information about the mathematics.
 
The lower voltages (18 volts and 24 volts) produced saturated colors (dark brown and dark blue, respectively). Nine volts produced a light tan, while 36 volts produced a light blue.
 
Titanium-anodized-1.jpg
Titanium-anodized-2.jpg
Voltages from 45 to 63 volts produced colors ranging from light green to light yellow to light yellow-pink.
Titanium-anodized-3.jpg
 
 Although light green supposed to be 50 volts while yellow-pink is 90, leaving the piece of titanium in the electrolyte for an extended period of time often makes the voltage seem higher than it really is (e.g. 45 volts makes a 70 volt color).
 
Because of the RMS difficulty mentioned beforehand, "70 volts" made a greenish-blue coloration, while "80 volts" made a lightly greenish coloration. Higher voltages made a whitish surface that was partially permeable to further titanium oxidation. This is when I realized the voltage problem. (I'm not sure why the purplish spot formed in the middle of the titanium.)
 
 Titanium anodized 4
Then I added the capacitor to see the real voltage. 55 volts made a lightly greenish surface. 
 
Titanium anodized 5
75 volts made an indigo-colored surface. 85 volts was purplish/indigo, while 95 volts was had a light purplish color.
 
 Titanium anodized 7
110 volts made a greenish color, while higher voltages made a whitish and faintly iridescent coloration.
 
Titanium anodized 8
 
Therefore, clean-cut charts about the anodization color when compared to voltage (like this are rather impossible to make. Extended periods of time in a solution at a particular voltage tends to show a coloration higher than what was expected. Momentary contact results in a lower-voltage color. Therefore, it is best to use a relatively low voltage like 45 volts for the lower colors (and 110 volts for higher colors) and just vary the time that the current is switched on to produce the different color effects.
 
Niobium, a similar metal, anodizes similarly to titanium. Anodized niobium jewelry is relatively common as it can be very colorful, durable, and hypoallergenic. Here is some anodized niobium.
 
Anodized-Nb.JPG
 
Here is the poster itself.
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April 24 2012 3 24 /04 /April /2012 13:15

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

 

Gadolinium is one of the more corrosion-resistant rare earth metals. In other words, it does not need to be kept in an ampoule or under oil to prevent rapid corrosion. Its trivalent compounds fluoresce green. Gadolinium compounds themselves, however, are white and boring.

 

In element form: No sources found.

 

In compound form: Some green phosphors contain gadolinium doped compounds.

 

I do not have any gadolinium samples at the time of this writing.

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April 23 2012 2 23 /04 /April /2012 13:22

I tried to extract pure chromium metal from a stainless steel spoon. It turned out to be much more difficult than I expected.

 

I had two extraction theories. One was to oxidize the electrolyzed chromium to chromate(VI), reduce it to chromium(III) in aqueous solution, precipitate it as chromium hydroxide, dry it, and react it with magnesium powder in a thermite-type reaction to make chromium metal.

 

Another was to use the chromium(III) in aqueous solution and electrolyze it to produce chromium metal at the cathode.

 

Trying it was a different matter.

 

First, I anodized the spoon in salt water solution. A huge amount of metal hydroxides were produced. I filtered them and placed the paste in sodium hypochlorite to oxidize the chromium(III) to chromate(VI). However, I did not realize that the inside of the huge lump of hydroxides still had a large amount of unoxidized iron(II) hydroxide. The oxidation from iron(II) to iron(III) used up most of the oxidative power of the bleach, severely diluting the solution.

 

Then, I reduced the light yellow chromate solution with ascorbic acid. It formed, as before, a light purple solution of some chromium complex. However, the resulting solution was by now so dilute that nothing could really be done with it.

 

I took a small portion, added hydrochloric acid and reacted it with zinc metal. No chromium(II) ions were produced in a measurable quantity.

 

I then took another portion, larger this time, and added some ammonia. Apparently, chromium(III) hydroxide forms a complex with ammonia, preventing it from precipitating anything.

 

I then reacted the previous ammonia mixture with sodium carbonate. Nothing precipitated.

 

I then took some more chromium(III) solution and reacted it with sodium carbonate. Nothing precipitate. Apparently, chromium(III) forms a complex with ascorbate.

 

I then electrolyzed some chromium(III) solution. Nothing happened.

 

I reduced the remaining chromate to chromium(III) to avoid environmental catastrophe and dumped down the drain.

 

 

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April 23 2012 2 23 /04 /April /2012 13:13

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

 

Europium is one of the more expensive rare earth metals, because of its high reactivity. For some reason, europium has a reactivity similar to calcium, corroding in moist air and reacting vigorously with water, producing the yellowish hydroxide. Europium is also the lightest rare earth metal. Most europium compounds are whitish but some are yellow; the sulfuric acid solution of europium(III) is reported to be pink.

 

In element form: No sources found.

 

In compound form: Europium-doped yttrium oxide is used to make phosphors in CFL bulbs. Red phosphors contain europium(III), while blue ones contain europium(II). Yttrium vanadata, used as a phosphor in mercury vapor bulbs, also contains a europium dopant.

 

Here is my sample of europium. It is a fluorescent bulb contain europium-doped phosphors.

 

Fluorescent-lamp.jpg

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April 21 2012 7 21 /04 /April /2012 13:26

This page will detail all of the ammine complexes that can be formed with various metals.

 

Copper(II): Copper(II) ammine complex  shows more information about this complex. This complex may be dried after being washed with an organic solvent, forming an extremely dark crystalline mass that tends to turn whitish in air. I have never done this without hydrolysis to insoluble copper hydroxide.

 

 Chromium(III): Chromium forms an ammine complex as well. It forms when chromium(III) chloride is reacted with excess ammonia.

 

Chromium-ammonia-chloride.JPG

Cobalt(III): Cobalt(II) forms several ammine complexes which easily oxidize in air to cobalt(III). I have yet to make some of these.

 

Nickel(II): Nickel(II) forms an ammine complex when nickel(II) chloride is reacted with excess ammonia. It is much bluer than other nickel solutions.

 

Nickel-ammine-complex.JPG

Silver(I): Silver forms a colorless ammine complex when silver chloride, oxide, carbonate, or nitrate is dissolved in ammonia. Upon standing, it can precipitate dangerously explosive silver nitride. It was used in the past to make silver mirrors by reacting with KOH and glucose.

 

Zinc: Zinc forms a colorless ammine complex when zinc hydroxide reacts with excess ammonia.

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April 21 2012 7 21 /04 /April /2012 13:17

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

 

Samarium is a rare earth metal that is more corrosion resistant than some of the earlier lanthanides. It is a divalent state, which compounds are strong reducing agents. Samarium(II) iodide is a greenish solid, while most of the trivalent compounds are yellowish or greenish as well. Samarium-cobalt magnets are the second strongest magnets, just behind NdFeB. They have a much greater heat resistance than the neodymium magnets. I tried to extract a pure sample of samarium chloride by dissolving the magnet in acetic acid, but some iron dissolved alongside the rare earths, contaminating the solution.

 

In element form: Samarium-cobalt magnets contain about 15% samarium metal. Mischmetal or ferrocerium contains about 1% samarium.

 

In compound form: No sources found.

 

Here is my sample of samarium metal. It is a complete samarium-cobalt magnet removed from a speaker. The shiny nickel plating is torn off in some areas, exposing the magnetic samarium-cobalt-misc. alloy.

 

Samarium-cobalt-magnet.JPG

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April 21 2012 7 21 /04 /April /2012 02:02

There are several super-strong acids that exist, with highly interesting properties.

 

Sulfuric acid: The most common of the strong acids, it is the acid that all other strong acids are compared to. Sulfuric acid does not have an extreme ability to protonate substances, but it is a highly reactive substance.

 

Magic acid: Containing antimony pentafluoride and fluorosulfonic acid, it was called this because of its ability to dissolve hydrocarbons such as paraffin wax. Dissolving a candle in this acid was a magic trick.

 

Fluoroantimonic acid: This acid contains antimony pentafluoride with hydrofluoric acid. This forms the extremely stable cation SbF6(-), leaving the hydronium ion quite bare.

 

Triflic acid: one of the earliest discovered superacids, this acid is relatively tame and in common use, but is still much stronger than sulfuric acid.

 

This is nasty stuff.

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