Tag Archive: DIY


If you’ve ever taken an organic chemistry lab class, you’ve probably done a melting point determination. That’s when you take a small sample of a solid, heat it up, and make note of the temperature at which it melts. This can be used to identify an unknown, but it is often used to assay purity. This is because impurities tend to make solids melt over a range of temperatures rather than at a single point, and because they tend to lower the melting point overall. There are fancy instruments you can buy which will measure melting points, but they’re so simple that I decided to make my own.

One way to do it is to use a Thiele tube, but I didn’t have one of those lying around. So I reached for my volumetric flask, filled it with mineral oil, and set it on a hot plate. Then, I put a tiny bit of the chemical vanillin into a capillary tube; this is my sample to test. I rubber-banded the capillary tube to a thermometer, such that the sample was next to the bulb. I set up a stand and clamped the thermometer in place, suspended in the mineral oil.

This would have worked, except that the samples used are typically so small that they are difficult to see with the naked eye. So I grabbed my USB microscope and clamped it in place, focused on the sample.

do it yerself

With my apparatus assembled, I turned up the heat and sat back to watch. Sure enough, between 80 and 82 degrees C. My copy of the Merck Index actually gives two melting point ranges for this compound, 80-81 and 81-83 degrees, which is a little confusing but seems to confirm that my melting point apparatus works as expected. Sweet!

melting

Today in LabLulz, I’m going to walk through a recent preparation I did in my chemistry lab: increasing and measuring the concentration of hydrogen peroxide.

WARNING: This procedure involves heat and the end product is a powerful oxidizer. Don’t get burned and don’t get it on yourself – wear gloves, splash-resistant goggles, and an apron. I had a spill of ~15%, all over everything, including myself. It was okay, but only because I followed safety protocols. I didn’t have the apron though, and I had to get pantsless.

Hydrogen peroxide is an interesting substance; it’s formula is H2O2, meaning that it is composed of two hydrogen atoms bonded to two oxygen atoms.

sdfsfasdf

Figure 1. Behold, the hydrogen peroxide molecule!

It is a powerful oxidizer, decaying into water and free oxygen. This is because the bond between the two oxygen atoms, called the peroxide bond, is unstable. Some substances which contain the peroxide bond are even explosive, like triacetonetriperoxide. Because it’s an explosive precursor, and somewhat dangerous on its own, concentrated hydrogen peroxide can be difficult to come by. The weak 3% solution found in drugstores is all that is available to DIYers, hobbyists, and other scientists outside of the mainstream chemical supply chain.

Fortunately, it is relatively trivial to increase the concentration from 3% to around 30%. There are several tutorials on the subject at YouTube (TheChemLife; zhmapper, nerdalert226) so I’m going to focus on measuring the concentration of the end product, a procedure which the videos tend to treat very qualitatively. I hope this tutorial will be informative and useful, even outside of punklabs; the process is easily generalized and density is important in many fields, including medicine and winemaking.

The concentrating procedure is pretty simple: pour about 500 mL of the 3% solution into a beaker and heat it, forcing the excess water to evaporate until there is a tenth as much liquid left (peroxide boils at 150 C, compared to 100 C for water.) There are only a couple of tricky points: the liquid must NOT boil, only steam – if it starts boiling, the peroxide will decay. Bits of dust and dirt will also cause disintegration, so the equipment must be kept very clean and free from scratches.

Okay, so after a few hours, I have about 50 mL of liquid. I drop a bit into a solution of corn starch and potassium iodide, and the mixture turns black, a positive test for oxidizers. I add a squirt to some sulfuric acid and copper wire, and the metal wire begins bubbling and the solution begins to turn blue with copper sulfate*. This reaction is faster and more vigorous than when I try it with the 3% solution, so I’ve clearly succeeded in increasing the concentration, but to what level? To answer that question, I’m going to measure the density of the solution. Continue reading

How did TopOc do on last year’s to-do list?

Not bad! As consistent readers might have noticed, the big news behind the scenes is that I have gotten involved in another production space, LumShop. Not only is it providing facilities for DIY Spectro development, it is also kindly hosting my chemistry lab! This will end well, I’m sure.

So what’s next?

  • Even more hard-hitting commentary and sass
  • More fractals and fungaloids!
  • Augmenting and measuring the concentration of hydrogen peroxide!
  • Third generation DIY Spectro!

Between this lineup and my lab, I’m sure the site will stay busy, but if you have any requests or suggestions, leave a comment!

There is a companion article exploring the issue from the perspective of environmental monitoring over at ArkFab.

Human influence on the environment has increased dramatically over the last 10,000 years, to the point that some geologists have argued that human reworking of the earth defines a new geologic age, The Anthropocene. (Zalasiewicz et al, 2008) Much of the focus has been on relatively robust, tangible changes in biogeochemistry. Examples include:

  • megafaunal extinction, accelerated erosion (Zalasiewicz et al, 2008) and nitrogen fixation resulting from the spread of intensive subsistence patterns
  • the loss of stratospheric ozone resulting from the release of novel chlorofluorocarbons

However, fleeting and less tangible effects are also important. Two examples are:

  • the light pollution resulting from urbanization and transportation infrastructure
  • changes in the acoustic environment resulting from direct addition of sonic energy and memes, as well as indirect sources.

A year-long composite view of the earth at night, showing human light generation. White lights are cities; blue lights are fishing boats; green lights are natural gas flares, and red lights are ‘ephemeral light sources’, interpreted as fires. Image from  NOAA National Geophysical Data Center – click for source + discussion.

Light pollution, the scourge of urban astronomers, is a well-accepted phenomenon with serious consequences. A 2004 review begins:

In the past century, the extent and intensity of artificial night lighting has increased such that it has substantial effects on the biology and ecology of species in the wild. We distinguish “astronomical light pollution”, which obscures the view of the night sky, from “ecological light pollution”, which alters natural light regimes in terrestrial and aquatic ecosystems. Some of the catastrophic consequences of light for certain taxonomic groups are well known, such as the deaths of migratory birds around tall lighted structures, and those of hatchling sea turtles disoriented by lights on their natal beaches. The more subtle influences of artificial night lighting on the behavior and community ecology of species are less well recognized, and constitute a new focus for research in ecology and a pressing conservation challenge. (Longcore & Rich 2004)

The amount of sonic energy released by human activity is recognized as an urban nuisance as well as an occupational safety concern. It also has recognized ecological effects: urban European robins have begun singing at night, when they have less acoustic competition. (Fuller et al 2007) Frogs have begun changing the pitch of their croaks in order to talk over traffic noise (Paris et al 2009)  In addition to sonic energy, human activity has released sonic memes into the environment. A meme is a self-replicating information pattern; jokes and computer viruses are two examples of memes. A person or computer acquires a meme and then spreads it, through retelling or infected emails. Sonic memes, such as ambulance sirens and cellphone ringtones, have been picked and repeated by songbirds. (Stover 2009) This is very interesting: human memes, the basis of Richard Dawkins’ ‘extended phenotype’ concept, have organically extended into other animals’ extended phenotype. (Recent reports of dolphins mimicking human speech are also very interesting in this context. The reverse flow also occurs, as animal communications are repackaged as ringtones or ambient music.)

Continue reading

dont forget the crystals

Magnesium sulfate crystals, clingin’ to a petri dish. Chillin’.

Another quick lab snap. These are some nice crystals I grew. I was washing an earlier, less photogenic crystal garden with alcohol, and catching the runoff in a petri dish. I let it evaporate and was greeted with this happy little accident! The crystals are magnesium sulfate, available as Epsom salt at most pharmacies.

haxor hijinx: a DIY hotplate

I have, once again, found myself at the helm of a DIY lab, this one with a chemical wetlab focus. I’m sure this will provide lots of material in the future; right now, I want to share a protip I came up with the other night. I have been using soda can alcohol stoves for heat, but this isn’t always appropriate. You can’t heat flammable mixtures, and they leave soot on my glassware. But I don’t have a hotplate yet! What’s a gutterpunk labnerd to do?

Don’t forget the boiling chips!

It’s won’t spin a stir bar, but a clothes iron will do fine as a hotplate! You can see that I’ve secured this one to the lab bench with wood and a clamp for extra stability.

 

 

DIY Spectro II

There is a more philosophically focussed companion article over at ArkFab.

At long last, second generation DIY spectro has arrived!

The spectrophotometer. Yes, that is an invisibility cloak. You can't see the stuff that's under it can you? Then that stuff is invisible!

If you recall, when last we left our humble spectrophotometer, it was a shambling mess of stone-age technology. Now, its a shambling mess of information-age technology!

Let’s take a closer look… Continue reading

A Detective Story

About to run the Final Qualifying Round for some second generation DIY Spectro, I placed the first blank into the cuvette holder, and pressed start (or rather ran python tryna.py; I’m tryna measure a spectrum, gosh!). The machine hummed into action, now that the motor control wire was plugged into slot 9, which the computer was communicating with rather than slot 2, which the computer was not.

A few minutes later I got the results: Nothing. The machine was not seeing any light. At all.

See, normally when I scan a blank sample, the detector (which has different sensitivities at different colors) shows a characteristic hill shape:

Some typical blank sample runs. Horizontal axis is motor position in degrees (0-180) and vertical axis is detector response. Black is the mean of the time series coming from the detector at a given motor position (1 sec data per degree); green is the standard deviation of the time series, and red denotes the maxima/minima. Time series were preprocessed to remove annoying serial communications glitches.

But when I ran this blank: Continue reading

DIY Spectro

UPDATE: There is a newer, more automated version of this project here, and an FAQ section here.

For the last while I have been concentrating on a project: developing an easily built spectrophotometer for low budget and DIY laboratories.

At the subatomic level, light is made up of entities called photons. Photons are electromagnetic vibrations; the speed at which they vibrate (in vibrations per second) determines the color of the light. Red light has a relatively slow vibrational frequency, while purple light has a faster one. The frequency also determines the energy that the the photon has: the faster a photon vibrates, the more energy it has. A photon of violet light has more energy than a photon of red light.

White light, like that from a halogen lamp, contains photons of a lot of different frequencies. However, you can use a prism or a diffraction grating to break that light up into its component colors, to get the familiar rainbow:

 

The spectrum of a halogen lamp

The above image is from a spectroscope I built during development. It’s made from bamboo, duct tape, pieces of beer cans, and an old CD: the perfect combination of steampunk, cyberpunk, and drunkpunk.

 

I did this spectroscope myself.

Continue reading

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