Experiment 66: Growing Large, Solid Tin Crystals

Encouraged by the success of my copper crystal growing experiment, I planned another metal crystal experiment - tin!  There are actually plenty of videos on growing tin crystals, but they all make terribly unsatisfactory small, flimsy crystals that can't even support their own weight out of water.  Using the same method I used for growing large, solid copper crystals, I successfully did the same for tin.

For this experiment, I initially used tin II chloride (about 90 grams per liter) acidified with a bit of HCl as the electrolyte.  A blob of tin and a strip of tin functioned as the anode and cathode, respectively.  As in my copper crystal experiment, the anode was on the bottom of my glass jar cell while the cathode poked into the electrolyte from the top.

The same sort of LM317 adjustable voltage regulator circuit was used, including the string of six diodes on the output.  Each diode drops a certain amount of voltage, so with a series of diodes, the lowest achievable voltage drops from the LM317's 1.25V down to about 0.25V.  This is critical for getting very low currents and slow crystal growth, which lead larger, more solid crystals.


I kept a thorough log of my observations during the experiment in a lab notebook, and the text of this may be viewed here.  The first try at growing the crystal worked fairly well, producing a solid result with some shiny crystal faces.  I couldn't really get the current to below 10mA or else it would drop almost discontinuously to 5mA.  I tried running the cell at 5mA, but I don't think tin was actually depositing.  A weird grey gunk started to grow at the cathode, and this turned out to be very brittle and crumbly out of water.  Upping the voltage just slightly to get ~10mA fixed the problem and tin crystals started growing again.  I also had to swirl the solution around a few times, and I think that this caused debris from the anode to get kicked up, which could have caused more small crystals to form, which is undesirable.  There was also some cloudiness at the end of this run, which may have been SnCl2 hydrolyzing in a not-acidic-enough electrolyte.  This should be avoided for best results.

To improve the experiment, I grabbed a small DC motor (probably scavenged from some dead electronics) and made a stir stick using an old plastic tube from a pen.  I powered the motor with another LM317 circuit so that I could get the lowest RPM.  This functioned as a very gentle agitator for the electrolyte cell to ensure the concentrations of tin chloride remained well-mixed.  Otherwise, the denser, more concentrated SnCl2 coming off the anode would stay at the bottom while the cathode would deplete the upper part of the cell of its SnCl2.  This seemed to work OK.  The resulting crystal did not have any grey gunk, but many of its crystals were smaller, though very solid.  There may have been more HCl in the solution than with the previous run; I had to re-acidify it to dissolve the cloudiness observed after the first run.

One interesting thing I noticed is that the tin anode made crackling noises as it cooled from being cast, and after using it as an anode, electrochemical etching showed some really neat crystals inside.
 I wonder if more metals would do this.

Still not quite satisfied with the crystals, I removed 30mL of the electrolyte from my cell (a tall glass baby food jar with a ~140mL capacity) and replaced it with tap water and a few drops of HCl (to ensure the solution stayed clear) for a new concentration of about 60g/L.  I used the same stirring technique as before, but this time, the crystal grew extremely quickly, taking less than 48 hours to grow to the bottom of the cell.  It also formed absolutely enormous crystal faces, with unblemished, flat, shiny parts a few centimeters long.  Through all three crystal growing runs, the current stayed below 15mA and the voltage was (according to the voltmeter) between 40 and 150 millivolts.  Thus, it seems that low current along with low(er) Sn2+ and HCl concentration is key to growing large crystals.

Once again, a microwave turntable motor was used for making 360° video of the crystals.  Unlike the copper crystals, these tin crystals do not tarnish, so they will retain their awesome shininess indefinitely.  :)  Perhaps it is time to try some new metals for crystal growing...

Cast a Mini Aluminum Skillet - Start to Finish

This actually happened a while ago but I just got around to posting the video.  I used a small cast iron skillet as a mold to make an aluminum skillet from melted-down vacuum cleaner parts.  Amazing!  A cast vacuum cleaner from the 1960s becomes a fully functional skillet useful for camping or making eggs.



I thought it would be helpful to explain how to do metal casting rather than only showing the pouring of the molten aluminum, so there are tips throughout the video aimed at those beginning casting.

MEL Science Chemistry Kits Review

Disclaimer: I was in no way compensated for this review, other than MEL Science generously sending me two free chemistry experiment kits along with their starter kit.

With the disclaimer out of the way, let's begin the review!  The basic concept is that upon subscription to MEL Science, they send you two chemistry kits each month.  You can then do experiments at home without needing to buy everything individually.
My first impression was that everything in the kit was well packed.  I did not find anything broken or damaged, and all the glassware was neatly padded so as to make breaking nearly impossible.  The starter kit has some good beginning materials - disposable plastic beakers (no more beaker-scrubbing!), a solid fuel stove, some glassware, etc.  It also has an instruction booklet on using the kits along with a detailed website that discusses the chemistry going on behind the scenes in the experiments.

The experiments themselves are on a variety of topics - I was sent one on combustion (The Chemistry of Monsters) and one on electrochemistry/redox reactions (Tin).  I enjoyed that the kits didn't require a lot of set-up work.  There wasn't anything to weigh out, plug in, or lay out.  In perhaps five minutes' time, I was doing actual experiments.

The tin dendrites experiment seemed to work well.  The dendrites grew beautifully, and the included macro lens took some stunning shots with my iPad 4 (sadly the MEL Science app does not support the iPad 4).

I tried one other experiment for the video, the sugar snake experiment from The Chemistry of Monsters.  As seen in the video, the hexamine solid fuel didn't quite fill the included mold, so its depression didn't hold all the sugar/sodium bicarbonate mix and the snake didn't work as well as pictured on the MEL website.  That was a small disappointment, but the sugar snake was still quite an intriguing experiment.  This simply shows that you may get different results as you try the experiments

In general, the MEL Science experiments seem to be "real"/unadulterated chemistry - they do dangerous and unique things like lighting off a Zn/S mixture and also have complicated concepts such as concentration cells.  They are meant to be suitable for most ages, so they won't be a substitute for a rigorous class in chemistry.  If, however, you are looking to explore, enjoy, and learn some unique chemistry, a subscription to MEL Science may be what you're looking for.

Experiment 65: Manganese Thermite from Batteries

A while ago, in Experiment 46: Manganese Dioxide Thermite, I attempted to make manganese metal for my element collection using thermite with manganese dioxide scavenged from batteries.  The experiment failed.  The batteries simply have too many contaminants (carbon, zinc oxide, etc.) to sustain a thermite reaction.

After reading some posts on ScienceMadness.org, I determined which steps would need to be taken to purify the manganese dioxide.  I first washed the manganese-containing battery paste with water and vinegar, then dissolved everything in HCl.  I filtered off my now-MnCl2 solution from the carbon, but it was contaminated with iron.  NurdRage's selective precipitation procedure came in handy for resolving that issue, and finally, I got a pretty pink solution - pure MnCl2!



I added NaOH to that solution to make manganese hydroxide, which oxidizes rapidly in air to Mn2O3, an oxide suitable for thermite.  After baking my hydroxide slush in the oven to help along the oxidation, I mixed my Mn2O3 with aluminum powder and lit it using a magnesium ribbon.  Unlike my previous manganese thermite attempts, this one violently flared up and reacted quite vigorously.
 Even better, I recovered some very beautiful shiny lumps of manganese metal.  While the thermite only gave a 23% yield on account of being so violent, it added another element to my collection, which is something to celebrate for sure.

Experiment 64: Homemade Napalm with Household Materials

A while ago, I saw a neat YouTube video on making napalm from Styrofoam and gasoline.  Making napalm is as easy as pushing Styrofoam into gasoline until it won't dissolve anymore.  I waited until I got a large block of Styrofoam from an appliance box and then tried making napalm in my own backyard.  :)

The Styrofoam dissolved surprisingly quickly, and it tripled the volume of the gasoline.  I only used about 10mL of gasoline, but that was plenty to make a good volume of napalm.  It had a consistency like silly putty, and it was very stretchy.  While saturated with gasoline, the napalm was slippery, but when it dried just a bit, it became tenaciously sticky.

I split my napalm into three blobs and lit one on an overturned paint can.  For its villainous reputation, napalm really isn't that interesting.  It just burns... and burns and burns and burns.  Each small chunk of napalm burned for over four minutes.

While the napalm itself wasn't super exciting, it did provide a neat photo opportunity.  I used my Nikon 1 J1 in manual mode to capture some really neat images of the flames.  The photos were all underexposed slightly to make the fire stand out, and I used a fast shutter speed to ensure sharp detail in the flames and toxic black smoke.  I took a lot of pictures as the napalm burned and then picked the best ones; at times, the flames had very beautiful contours.  Although napalm may be unexciting as far as fireballs go, it certainly provides a good subject for the amateur photographer.

Casting a 3D Aluminum Puzzle Cube

As I was searching for another casting project to hone my skills on, my eyes fell upon an injection-molded 3D puzzle cube made by Proto Labs.  The cube had nine plastic parts that all fit together to make the cube.  It fit the bill for an interesting casting project, so I started by planning out how each piece would be oriented in the casting flask.  I wanted to be able to pull them straight out of the sand without having undercuts.  The plastic parts were hollow with one side missing, so I had to put tape over the missing side so that I would cast solid aluminum parts.

After all the pieces were taped, I laid them in a circle in my casting flask.  I positioned them close together so that the aluminum would only have to travel a short distance to fill the mold.  Then, I dusted the parts in baby powder and sprinkled on casting sand, packing as I went.  To make the other half of the mold, I first flipped the initial mold half over and then cut away sand that had gotten under the yellow piece.  The yellow piece was tricky because it had an overhang/undercut in all orientations.  Thus, I had to cut away the sand under the overhang so that I could later pull the piece straight out of the mold.

With the first half complete, I dusted everything with baby powder again and then packed sand into the second half of the mold, which fit on the first half with wooden pegs.  When both casting flasks were finished, I pried the halves apart and carefully teased the pieces free from the sand.  I then cut a sprue and gate system to feed metal to the pieces.  The sprue and gate system should have rounded corners as much as possible to minimize sand erosion by molten aluminum.  I did not make any vents for the casting, as the pieces were fairly small.

Outside, I melted a full crucible of aluminum and heated it for three minutes after the last piece of scrap melted to bring it up to pouring temperature.  Then, I sprinkled sodium carbonate and sodium chloride on in a 50/50 ratio and scraped off the dross/flux mix.  I poured the shiny liquid aluminum down the sprue, and half an hour later, I broke open the mold to reveal a casting that looked somewhat like an ancient Mayan symbol.

Using a hacksaw with a metal blade, I cut each piece free from its gate and began filing.  Injection molding is quite different from sand casting, so the pieces weren't designed to be sand cast, and they were fairly rough straight from the mold.  My strategy for filing them was to file two pieces until they fit together and then file additional pieces to fit the previously filed ones.  I began with the orange and red pieces and ended with the green piece, since it holds the cube together.  I found that filing the edges and corners of the pieces greatly improved the cube's appearance, so I did that, using a Dremel tool to get in the hard-to-reach corners.  In total, I filed for 12 hours.  It was quite awful.

When all the pieces fit, I sanded them with progressively finer grits to remove the scratch marks left from filing and sanding.  I finished by sanding everything with a worn-out sanding sponge, which gave the cube a nice shine.  When looked at from a corner, the cube appears to be a 3D maze, which I think is pretty neat.  Although the cube was a lot of work and took an obscene amount of filing to finish, it was well worth it in the end.  Nothing worthwhile is ever easy... still, I'm never doing this much filing again!





Experiment 63: Purifying Potassium Chlorate from Matches

For a while, I have wanted to make flash powder, a mixture of potassium chlorate or perchlorate and aluminum powder.  Like nitrocellulose, it burns with a flash when unconfined, but it will explode if confined.  One easy (if expensive and time-consuming) way to get potassium chlorate is through purification from match heads, so I decided to try the process on a handful of matches.  I used this video as a reference for the experiment.

I began the experiment by crushing around 50 match heads into a powder.  For cardboard matches, I simply snipped the head off and then pulverized it, but for wooden kitchen matches, I crushed the powder off the match and discarded the matchstick.  Once I had a fine powder, I poured in about 100mL of water and stirred to thoroughly dissolve the potassium chlorate.

There were a lot of bits of floating cardboard, so I filtered the mixture through a coffee filter to separate the green-colored solution from the insolubles.  I also washed the cardboard with water to recover any soaked-up chlorate solution.  Then, I boiled the green liquid down to about 1/10 of its original volume and set the beaker aside to cool.  When it had cooled to room temperature, I placed it in an ice bath to precipitate as much chlorate as possible.  As the solution cools from boiling to freezing temperatures, the potassium chlorate's solubility drops, so it precipitates as solid crystals.

I filtered off my crystals using another coffee filter and then washed these with acetone to remove some of the green dye; obviously, I didn't get all of it.  Potassium chlorate is not soluble in acetone, so this step does not remove any potassium chlorate.  Then, I let my crystals dry and weighed them.  From around 50 matches, I got 1.5g of fairly pure potassium chlorate.  Combined with aluminum powder, this is sure to make a brilliant flash.

Experiment 62: Explosive Copper Thermite!

Copper thermite is notorious for being violent and even explosive, so naturally, it was next on my list of thermites to try.  I began by weighing my 49.25g of copper (II) oxide made in Experiment 54: Making Copper Oxide for Thermite.  I divided this mass by 4.42 (derived from stoichiometry) to get the required mass of homemade aluminum powder, which was 11.12g.  I mixed them thoroughly to ensure a fast reaction and then set aside 45g for later.  With the 15g I now had, I used a homemade electric match (wire filament + kitchen match) to ignite it with the press of a button.  I wanted to capture the reaction on slow-motion, but my Nikon 1 J1 only records slow-motion for five seconds, so I had to have the thermite ignite at a precise time.  The electric match was better for this than a magnesium ribbon.

I was quite impressed by the speed and violence of the reaction.  It was all over in less than a fifth of a second, and the cloud of smoke it created made a smoke ring at least a yard in diameter.  It was quite amazing to see.

I wanted to make molten copper with the rest of the thermite.  Since my unmodified copper thermite blew everything out of the paper cup I put it in, I diluted my copper thermite with 17g of borax powder in a 2.5:1 ratio.  In a previous small-scale test, the borax had slowed the reaction and acted as a flux to liquefy the alumina slag created by the thermite.  This helped separate the molten copper from the slag.  Since this thermite reacted more slowly, I ignited my large batch of it using a magnesium ribbon.  It started off well, but then the thermite fizzled and continued to sputter for a few minutes.  Since my small-scale test of the composition worked well, I think that the large batch didn't perform because I had lightly pressed the thermite down before igniting it.  Maybe this didn't let the fire travel quickly enough.

Although the slow thermite was a bit of a disappointment, it did make solid copper pebbles, which is more or less what I was aiming for.  I used a hammer to pulverize the slag and then washed the mix with water to float away the less-dense slag.  This actually separated the copper out quite well, and in the end, I recovered 3.55g of copper granules.  This is a 9% yield, which isn't terrible, considering the thermite seemed to sputter instead of flaring up nicely.  In any case, my expectations were "blown away" by the fast copper thermite smoke ring, so I consider this experiment a success.

Experiment 61: Single-Transistor Ion Chamber for Detecting Radiation

Radiation fascinates me, but it isn't very interesting unless you can detect it somehow.  Geiger counters cost a lot, so I built something a radiation detector using a soup can and a single transistor.

The ion chamber I built uses a thin whisker wire inside a metal can to collect charge from ions made by passing radiation.  The transistor (I used a BC547B, but any small NPN signal transistor should work) amplifies the difference in charge between the can and the wire and sends this out as a voltage read out on a multimeter.  The other components of this simple radiation detector are a 4.7kOhm resistor, a 9V battery clip, and a 9V battery for power.  My whisker wire was simply some bare wire that held its shape when straightened.  I got my design from this YouTube video, and the video's instructions seemed fairly clear.

I learned some important things through researching this ion chamber.  When picking a can, it is important to pick one without a coating on the inside (or sand it off).  Any coating interferes with picking up charge from the air, which hampers the detector's performance.  I sanded my can's inside to be sure it would work.  Also, the transistor gets epoxied to can.  The epoxy shouldn't touch any of the transistor leads (only the plastic), and the leads shouldn't touch the can.  Either of those situations would cause unwanted electrical conductivity.  The only electrical connection to the can is made through the 4.7kOhm resistor.  If there is a coating on the outside of the can, it should be sanded off to help make a good electrical connection with the resistor.  When attaching the whisker wire, it is important to make sure it doesn't touch the can as it goes from the transistor's base through the hole in the can bottom (see picture at right).

One problem with this design is its sensitivity to external electromagnetic fields.  Simply moving sometimes causes the measured voltage to fluctuate.  To help prevent this, the detector may be closed off with an aluminum foil "lid" with the radiation source inside.  I also made an electronics cover using the bottom of another soup can and taped it over the electronics with some foil tape (as seen in the two pictures below).

Using the detector is simple.  With a 9V battery connected, exposing the detector chamber to radiation creates an increased voltage readout on a connected multimeter.  I have tested this detector with an americium source and with uranium ore, and while both work, the americium definitely has a greater effect.  Sadly, I do not have any other radioactive items to test; if I did, I would check whether this ion chamber can sense beta and gamma radiation.  Still, I am truly amazed at what can be accomplished with just a soup can and a single transistor.

Experiment 60: Anodizing Titanium into Rainbow Colors

A very long time ago, I received some scrap rods of titanium.  One of titanium's really neat properties (it has several) is that it can be anodized into a rainbow of colors.  Unlike aluminum anodizing, where the created aluminum oxide layer is colorless and a dye is needed, titanium anodizes to create what is known as thin film interference.  Basically, light waves entering the transparent oxide layer created by anodizing interfere with each other, making new waves and colors.  Other metals like niobium and tantalum also have this effect.  I thought anodizing titanium looked really fun, so I slapped together an anodizing experiment.

For my anodizing bath, I used 200mL of tap water with 8 grams of Borax dissolved in it.  Then, I sanded my titanium and cleaned it with acetone.  It is important to not leave fingerprints on the surface.

I looked at this image to see which voltages anodized titanium to nice colors.  Then, I connected the number of 9V batteries necessary to achieve that voltage.  Some batteries were at a bit less than 9V, so my first voltage I used was 24V (three batteries).  I connected my titanium to the positive on my battery series and clipped a piece of aluminum to the negative.  After putting both electrodes in my anodizing bath for half a minute, the titanium had turned a bright blue color!

I wanted to try making a pattern, so I cleaned my blue titanium with acetone again and then cut a tiny square of electrical tape into the letters "Ti."  I carefully applied the tape letters to the titanium, being sure not to leave skin oil on the metal.  Then, I put the titanium back into the bath, this time using 57V (seven batteries).  I wasn't happy with the faint yellow color that voltage made, so I tried again with 73V (nine batteries).  That gave a nice pink color, so I took the titanium out and removed the tape.  The pattern had worked, and I now had beautiful blue letters on a pink background.  The experiment only took half an hour, but it had great results!

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