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April 20 2012 6 20 /04 /April /2012 13:16

Promethium, being an extremely radioactive and unstable element, is impossible to obtain in pure form. However, some old glow-in-the-dark watches that are radioactive have used promethium as the radioactive element. This is after the radium watches were discontinued and before tritium came into more common use.

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April 20 2012 6 20 /04 /April /2012 01:52

 

What temperature can be reached with a three-inch magnifying glass in direct sunlight?

 

1. Indium melts when directly focused on it. Indium has a melting point of 156.6 degrees Celsius. At least this temperature can be reached by focusing the light onto a shiny piece of metal.

 

To get a higher temperature, I needed to use a dark surface. I charred the surface of a piece of wood with the magnifying glass and placed my metal sample on the dark surface. Upon focusing the light, the metal melted.

 

2. Tin, bismuth, and lead easily melted. Their respective melting points are 232, 271.5, and 327.5 degrees Celsius. All of these temperature are easily reached by using this method.

 

3. Zinc melts with difficulty, requiring an extended period of time to warm. Zinc has a melting point of 419.4 degrees Celsius.

 

4. Magnesium burns with difficulty. This will not work with a large piece of magnesium; to get the magnesium to burn I cut a thin strip of the foil and focused the light on the super-thin and fragile end. Magnesium autoignites at 473 degrees Celsius. Hotter temperatures may be reachable but not very easily by such a primitive method.

 

5. Titanium does not burn using a dark charred wood base. The wood turns white due to ash formation and disappears from under the titanium, never allowing it to reach the maximum temperature. Titanium autoignites at 1200 degrees Celsius. A different method will need to be tried to determine if this temperature can be attainable.

 

 

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April 19 2012 5 19 /04 /April /2012 18:51

I have finished my second semester of general chemistry labs. I have had a generally positive experience with them academically, although there is some to be desired scientifically. Here is my opinion on ways to improve the chemistry labs in general chemistry.

 

1) There should be more questions on the lab reports that make students do some research about chemistry. This should not be inevery question, but once in a while, there should be an unknown result which will have to be researched. Also, the practical aspects of the labs and their use in a real-life setting can be mentioned, to help connect the student's learning to their career (if they are planning on a chemistry-related career).

 

2) Providing problems which will have to be solved by existing chemistry knowledge will help students apply all that they have learned about chemistry to synthesize a solution or a compound, for instance.

 

3) Do not do all of the preparation work for the students. Allow them to make their own solutions, fill their own burets, etc. This will help enforce the basic concepts such as molarity and molality much more than having everything done already. Maybe even leave some leeway in the instructions instead of providing a point-by-point process that can be followed without thinking or learning.

 

4) Perform some interesting and some perplexing demonstrations occasionally to get students interested in the course more.

 

5) Lab write-ups should be more thorough for those labs which are more complex. Obviously, there is not much to write about in a titration lab, for example, but other labs will benefit from a longer write-up.

 

Here are some things that are already good in the labs.

 

1) The labs are not too long, which helps the student to keep the goal in mind.

 

2) The instructors were very helpful and ready to fix any problems that the students might have.

 

3) Some of the experiments were quite thought-provoking for me as they did not produce the expected result or the results were just plain interested (mercury amide is just a weird and interesting-sounding compound).

 

I may expand this later.

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April 19 2012 5 19 /04 /April /2012 18:44

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

 

Neodymium is one of the more reactive rare earth metals. It forms one oxidation state, +3, and has the unique property of color-changing salts. A solution of neodymium chloride, pink in sunlight, may appear light grayish-yellow in fluorescent light. Neodymium oxide ranges from blue to purple to pink.

 

In element form: Neodymium magnets contain about 14% neodymium. Mischmetal has a small amount of neodymium in it.

 

In compound form: "Daylight" incandescent light bulbs often use neodymium oxide to make them bluish (fluorescent) or purplish (incandescent or sunlight) colored. The color change indicates the presence of neodymium.

 

Here is my sample of neodymium. It is a neodymium magnet.

 

Strong-magnet.JPG

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April 18 2012 4 18 /04 /April /2012 20:24

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

 

Praseodymium is one of the more reactive rare earth metals. It forms a trivalent state, like all other lanthanides, that is light yellow-green. Outside of aqueous solution, praseodymium forms some higher oxidation state compounds like the oxide.

 

In element form: Mischmetal contains a small amount of praseodymium. Carbon arc lamps used in film photography contain praseodymium at their cores.

 

In compound form: Some yellow colored glass is colored using praseodymium(III) oxide.

 

Here is my sample of praseodymium. It is a piece of mischmetal.

 

Mischmetal in water

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April 17 2012 3 17 /04 /April /2012 15:37

Magnesium powder or shavings are useful in many experiments in amateur chemistry as a reducing agent. It is also interesting to burn, although repeated burning is discouraged due to the production of harmful UV rays. There are several ways to obtain magnesium in a more finely divided form.

 

Buy it: You can buy magnesium turnings for a relatively low price ($4.50 for 50 grams at AlphaChemicals). However, magnesium powder has some shipping restrictions on it.

 

Knife: When a magnesium bar is scraped, large shavings and flecks of magnesium metal come off. These flecks are useful for reductions and sparkles in pyrotechnic compositions but are less than ideal for thermites or other reactions that need a finely divided form of magnesium.

 

File: I have found a file to be the best way to create small amounts of finely powdered magnesium. Rubbing the magnesium against the file over a piece of paper allows the magnesium to be collected on the paper. It can later be mixed in with any oxidizer and used to create a variety of energetic mixtures.

 

Steel grinder: Electric grinders, though much faster than hand, tend to create air currents that blow most of the superfine magnesium powder away. Powder can be created this way but with a large amount of waste.

 

My first thermite reaction burnt relatively quietly as it used magnesium shavings. The last one, which used a similar oxidizer with magnesium powder, burnt much more rapidly, noisily, and quickly, showing the benefit gained by using powder (generated by a file) instead of shavings.

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April 17 2012 3 17 /04 /April /2012 15:31

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

 

Note: Since the rare earth metals are so similar to each other, I will only include the differences in the description to avoid constant repetition.

 

Cerium is one of the rare earth metals that is more susceptible to aerial oxidation, so it is normally kept under oil or in an ampoule. Cerium forms two oxidation states, a trivalent state which is stable in acidic aqueous solution and colorless under normal circumstances, and a tetravalent state. This state is more stable as a compound, not an ion, and so it is found in basic solution. Cerium dioxide is light yellowish, while other cerium compounds like the sulfate are very bright orange or yellow.

 

In element form: Ferrocerium contains about 50% cerium.

 

In compound form: Cerium dioxide is used as an abrasive and a polish. Some tungsten arc welding electrodes are "Ceriated" with 2% cerium dioxide.

 

Here is my sample of cerium. It is a piece of mischmetal, just like lanthanum.

 

Mischmetal (1)

 

Feel free to view the category "Elements" below for information on obtaining the other elements.

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April 14 2012 7 14 /04 /April /2012 13:28

Trivalent iron has a significant amount of oxidative power to it. Here I will list some of the reactions of this common yet interesting substance.

 

Thermites: Iron(III) oxide (or red iron oxide) is one of the most common ingredients in thermites. Iron thermites tend to burn extremely hot, yet without much violence, allowing a prolonged heating of the supporting materials. See Magnesium - iron(III) oxide thermite for my experience with an iron(III) oxide thermite.

 

Most of the other experiments involve trivalent iron in aqueous solution as a chloro complex. To make this, iron(III) oxide is dissolved in hydrochloric acid and the resulting brown and highly acidic solution is the starting point.

 

Iron: Iron comproportionates with iron(III) chloride, forming a greenish solution of iron(II) chloride. This reaction goes to completion, as evidenced by the complete whiteness when the solution is neutralized with sodium carbonate. See Comproportionation Reaction for other comproportionation reactions including the iron one.

 

Nickel: Nickel reacts with iron(III) chloride, producing a green solution of iron(II) and nickel(II) ions. While nickel dissolves very slowly with hydrogen peroxide/hydrochloric acid and dissolution is almost nonexistent with pure HCl, nickel dissolves quite rapidly in trivalent iron solution.

 

Nickel-and-iron-III--chloride-reaction.JPG

Copper: Copper reacts with iron(III) chloride, forming copper(II) and iron(II) ions. However, copper(II) reacts further with copper, producing white and insoluble copper(I) chloride. This then further reacts with more copper(II) chloride, producing a brown solution. This breaks up when diluted with water to white copper(I) chloride and green copper(II) chloride again.

 

Bismuth: Bismuth dissolves extremely slowly and incompletely in iron(III) chloride solution. When the resulting solution is diluted, some bismuth hydrolysis is noticed.

 

Tin: Tin reacts with iron(III) chloride solution, forming tin(IV) ions and iron metal. Since tin and its divalent ion are both relatively strong reducing agents, they reduce iron(III) all the way to iron metal.

 

Tin-and-iron-III--chloride-2.JPG

Lead: Lead reacts with iron(III) chloride, forming insoluble lead(II) chloride and iron(II) ions. However, the reaction does not run to completion because the lead(II) chloride forms an impermeable layer.

 

As you can see, iron(III) is quite a reactive substance, reacting with and reducing most metals. That is why it is used as an etchant.

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April 14 2012 7 14 /04 /April /2012 13:19

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

 

Lanthanum is a relatively soft and reactive metal of the rare earth metal group. The first member of its group, it forms white or colorless trivalent compounds, making its aqueous chemistry boring. Lanthanum is found with all the other rare earth elements.

 

In element form: Mischmetal contains about 45% lanthanum, while ferrocerium contains about 30%. Lanthanum alloy is found in the anode of a nickel metal-hydride battery. (Be careful when opening these batteries, risk of fire.)

 

In compound form: No sources found.

 

Here is my sample of lanthanum. It is a piece of mischmetal. The presence of rare earths is indicated by the formation of hydrogen and slimy hydroxides when in contact with warm water.

 

Mischmetal-in-water.JPG

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April 13 2012 6 13 /04 /April /2012 14:23

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

 

Barium is a soft, silvery gray metal of the alkaline earth metals. It is the heaviest member of the group that is not radioactive, and also the most reactive. Barium metal reacts vigorously with water, producing soluble barium hydroxide. Barium easily absorbs oxygen and nitrogen from the air when heated. Barium is quite toxic in its ionic form, making it useful as a rat poison.

 

In element form: Barium metal is used in vacuum tubes and CRTs to absorb any leaking gases. It is visible as a reflective crown on the inside of a tube, but probably not visible in a CRT.

 

In compound form: Barium sulfate is used to map the digestive tract because it is opaque to X-rays. Barium ferrites are used in credit card magnetic strips. Electrodes in fluorescent lamps are coated with barium oxide to increase the emission of electrons. The screen of a CRT has barium oxide in it to help absorb the radiation.

 

Here is my sample of barium. It is a vacuum tube obtained from a friend who has a stock of them. The barium is visible on the right side.

 

Vacuum-tube.JPG

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