Get Clear Insights Into Cloudy Water With The Open Colorimeter

A basic scientific tool for chemistry and biology is a colorimeter device used to measure which wavelengths of light a particular sample solution absorbs. Some applications of colorimeters are measuring pH or chlorine levels, measuring pollutants, such as oil or pesticides, and, in some cases, can even be used to measure RNA/DNA concentrations. Even most washing machines today have a specialized colorimeter sensor, of sorts, to measure turbidity (cloudiness) to provide feedback on the cleaning process. To help in building your home scientific lab, [IORodeo] has released an Open Colorimeter.

A blown out diagram of the Open Colorimeter showing the 3d enclosure, the PyBadge, the LED board and sensor along with text describing each element

The Open Colorimeter is a self-contained device that accepts cuvettes filled with liquids for testing. The basic structure is an LED mounted onto a board that shines through the cuvette filled with a sample that is then measured at the other end by a TSL2591 color sensor. The Open Colorimeter has separate specialized LED boards for a range of wavelengths from 470nm to 630nm and incorporates a PyBadge that serves as the main microcontroller, as well as display and input.

[IORodeo] has done extensive documentation on the assembly, usage, and testing of the device. They have also provided protocols for the measurement of Ammonia, Nitrate, Nitrite, and Phosphates in addition to providing resources for absorption profiles of many other substances. All files relating to the 3D enclosure, firmware source code, schematics and Gerbers are provided under an open source hardware compatible license. For those not wanting to build it themselves, [IORodeo] is offering them for sale.

This isn’t the first time we’ve featured colorimeters, with some building a DIY version and others using it in a Tricorder project. The Open Colorimeter is a nice addition to this list and is ready for hacking and extending!

A home-made colorimeter

Classic Colorimeter Clone Calibrates Cuvettes’ Contents

For anyone dabbling in home chemistry, having access to accurate measurement equipment can mean the difference between success and failure. But with many instruments expensive and hard to find, what’s a home chemist to do? Build their own equipment, naturally. [Abizar] went ahead and built himself a colorimeter out of wood and spare electronic components.

A colorimeter (in a chemistry context) is an instrument that determines the concentration of a solution by measuring how much light of a certain wavelength is absorbed. [Abizar]’s design was inspired by the classic Klett-Summerson colorimeter from the 1950s, which uses a light bulb and color filters to select a wavelength, plus a photoresistor to measure the amount of light absorbed by the sample. Of course, a more modern solution would be to use LEDs of various colors, which is exactly what [Abizar] did, although he did give it a retro touch by using an analog meter as the readout device.

The body of the colorimeter is made from laser-cut pieces of wood, which form a rigid enclosure when stacked together. The color wheel holds eleven different LEDs and is made with a clever ratchet mechanism to keep it aligned to the cuvette, as well as a sliding contact to drive current into the selected LED. All parts are painted black to prevent stray reflections inside the instrument, but also make it look cool enough to fit in any evil genius’s lab. In the video embedded below, [Abizar] demonstrates the instrument and shows how it was put together.

While we haven’t seen anyone make their own colorimeter before, we have seen DIY spectrophotometers (which measure the entire absorption spectrum of a solution) and even building blocks to make a complete biochemistry lab.

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Coffee, Conspiracy, And Citizen Science: An Introduction To Iodometry

I take coffee very seriously. It’s probably the most important meal of the day, and apparently the largest overall dietary source of antioxidants in the United States of America. Regardless of whether you believe antioxidants have a health effect (I’m skeptical), that’s interesting!

Unfortunately, industrially roasted and ground coffee is sometimes adulterated with a variety of unwanted ‘other stuff’: corn, soybeans, wheat husks, etc. Across Southeast Asia, there’s a lot of concern over food adulteration and safety in general, as the cost-driven nature of the market pushes a minority of vendors to dishonest business practices. Here in Vietnam, one of the specific rumors is that coffee from street vendors is not actually coffee, but unsafe chemical flavoring agents mixed with corn silk, roasted coconut husks, and soy. Local news reported that 30% of street coffee doesn’t even contain caffeine.

While I’ve heard some pretty fanciful tales told at street side coffee shops, some of them turned out to be based on some grain (bean?) of truth, and local news has certainly featured it often enough. Then again, I’ve been buying coffee at the same friendly street vendors for years, and take some offense at unfounded accusations directed at them.

This sounds like a job for science, but what can we use to quantify the purity of many coffee samples without spending a fortune? As usual, the solution to the problem (pun intended) was already in the room:

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Making High Concentrations Of Hydrogen Peroxide At Home

Hydrogen peroxide – the same stuff you can pick up from a drug store or beauty supply store – is one of those very interesting chemicals that belongs on every maker’s cabinet. At concentrations of about 30%, it’s perfect for etching PCB boards, and at even higher concentrations – about 70% – it can be used as rocket fuel. Unfortunately for the home hacker, it’s very difficult and expensive to obtain peroxide in concentrations above 3% or so. That’s alright with [Charlie], though, because he’s come up with a way to concentrate peroxide and measure the concentration once he’s done.

There are a few YouTube videos of kitchen chemists concentrating peroxide by heating it on a stove to just under 100°C. Because hydrogen peroxide boils at 150°C, they’re simply boiling off the water and increasing the concentration of peroxide. This is a qualitative method, and you’ll never know what concentration you’re getting. [Charlie] rigged up a small-scale with a pipette to measure the weight of his concentrated peroxide per unit of volume, giving him the density of his concoction and thus the concentration.

We have to note that concentrated peroxide is dangerous stuff, but the results of [Charlie]’s lab work aren’t much more dangerous than what hair stylists work with every day. If you’re going for high-test peroxide, good job, that’s awesome, but do be aware of the risks.