A blast from the past: An Evelyn Colorimeter

For the past several years I have been working on a manuscript for a book on the use of colorimetric methods for the quantification of organic molecules. One of the major landmark pieces of equipment that I kept reading about was the Evelyn Photoelectric Colorimeter; it is basically a quaint little wooden box that put an affordable spectrophotometer into laboratories the world over. This was one of the pieces of essentially ended the days of comparators (devices in which you compare the color intensity of a sample to a reference material) which were often subjective and contributed semi-quantitative work at best. I myself used a comparator which used long Nessler tubes for comparing the color of liquid samples, which a bit of skill it isn’t so bad although having an unbiased eye was not always easy.

The Evelyn Photoelectric Colorimeter was the handywork of Kenneth Evelyn, hence the name of the device. Kenneth Evelyn published a paper in the Journal of Biological Chemistry title “A Stabilized Photoelectric Colorimeter with Light Filters” in 1936 (Evelyn, 1936; which can be viewed here). The design, while simple by today’s standards, was a major step forward in the field of spectroscopy. Perhaps unsurprising given the truly ground-breaking nature of this instrument, Kenneth Evelyn filed a patent in 1938 (United States Patent 2193315) for this photoelectric colorimeter for “biological” work. Consisting of a photocell and drop-in colored filters, the device put a cost-effective colorimeter into reach of many laboratories, ranging from industrial labs to clinical settings. Prior to this, a lot of chemical analysis consisted of traditional “wet” chemical methods such as titration, gravimetric methods which involved forming a precipitate and weighing the amount of material recovered, or the aforementioned color comparison methods in the event of a reaction that forms a chromophore.

Anyway, Kenneth Evelyn and a coworker (Helga Tait Malloy) published a paper on the colorimetric determination of Bilirubin using this device in the Journal of Biological Chemistry in 1937 (link) which is regarded as one of the landmark papers in clinical chemistry. A flood of other highly cited paper quickly followed which quantified a wide range of molecules using colorimetry including a high cited method for determining phosphorous published in the Journal of Laboratory Clinical Medicine.

A bit about spectroscopy and how we use light to measure stuff

The basic principle behind colorimetry, and spectroscopy in general, involves the principle of absorption and transmittance. Some types of molecules absorb light very strongly at specific wavelengths allowing their concentration to be measured if you can measure the amount of light transmitted through a sample at a given wavelength. The amount of light that is not transmitted to the sample due to absorption can be used to infer the concentration of a particular analyte. For those of you that have taken a course in college chemistry or biology have probably heard this referred to as Beer’s law, or more accurately the “Beer-Lambert law”, which is described by the equation:

Where A is the amount of absorbed light, I0 is the light intensity shining into a solution and I is the amount of light that makes it through the solution. So the cloudier the solution, the less light make it through or is absorbed. As you might guess, the amount of light absorbed by a solution is dependent on a few things, namely the concentration of the stuff that does the absorbing, the wavelength of light, and how “absorby” a particular thing is.

In this equation, A is again absorbance (at a specific wavelength), ε (epsilon) is the molar extinction coefficient (basically a measure of how “absorby” a particular molecule is for a specific wavelength of light), l is the pathlength (usually 1 cm to make the math easier!), and c is the concentration of a particular molecule. The beauty of this is that if we can measure the absorbance of light through a solution, we can infer the concentration of a particular molecule that absorbs at this wavelength! This technique has been widely applied to all sort of molecules over the past 100 years, from protein in blood and urine, to the amount of oxygen in the blood stream bound to hemoglobin, and literally tens of thousands of other kinds of molecules!

On the “absorby-ness” of a particular molecule as a function of the wavelength of light, consider carbon dioxide (which is something like 400 ppm in the atmosphere at the time of writing). Carbon dioxide gas lets visible light through with no problem, yet, infrared light is absorbed. If we could see infrared light, the world around us would appear to be very dark given how “absorby” CO2 is for light in this part of the spectrum!

The Big Find

About two or three years ago I stumbled upon the Science History Institute’s page where they have a photograph of an Evelyn Colorimeter (link here) and I have to say that I was taken back by the elegance of the design. There is something about the appeal of a wood box. And one that does science? I´d love to have one especially given my love of spectroscopy. Unfortunately, I figured such a think would be well out of my reach if such things are even still floating around out there!

In the spring of 2021, I stumbled across an Ebay listing for an Evelyn Colorimeter for $150 (USD). I could not believe the price for such an amazing artifact, and one in seemingly in fairly good condition given its age. Before I could bat an eyelash, I had my credit card number entered and a confirmation email in my inbox.

The arrival and a closer inspection

Upon receiving the Evelyn Colorimeter (Figure 1), the first thing that struck me when I opened the box was the unmistakable aroma of antique wood. It smelled absolutely fantastic. The potent yet gentle scent of the wood reminded me of my grandmother’s walk-in closet in her bathroom. Lifting the instrument out of the box, I was amazed at how sturdy it felt. The feel of 70+ years of grime on the surfaces was unmistakable. All things consider, I’m nothing short of amazed at how well this instrument has stood up against the passage of time.

Figure 1 – The Evelyn Photoelectric Colorimeter

As can be clearly seen from the name plate on the front, this instrument was manufactured by Rubicon in Philadelphia. Later iterations of this instrument were made by Honeywell (which still exists today).

The top of the instrument, home of various knobs and switches, is a stainless steel plate (Figure 2). On the left, we find the switches that control the lamps for the “galvanometer lamp” and “colorimeter lamp”, and the middle hosts a tube for slide a sample in with a slot for the desired wavelength filter (more on that later), and on the right we´ve got course and fine adjustment knobs.

Figure 2 – The top of the Evelyn Photoelectric Colorimeter

On the top metal plate, there is a hand etched inscription that reads “149-11-9” (which can be seen a bit more easily in Figure 3 below). I am not sure what significance these markings are but I have to wonder if this particular instrument was manufactured in 1949.

Figure 3 – The top panel is etched with several numbers etched at the bottom center

Figure 4-6 –

Figure 4 (left) – The switches on the left side of the instrument panel definitely have some wear after some heavy useage

Figure 5 (center) – The sample holder and filter slot

Figure 6 (right) – Even more grime!

The Evelyn Colorimeter that I purchased only came with a single filter (660/690 nm) although the seller displayed a 565 or 585/640 nm filter holder and a few other filters that didn’t make it to me for some reason (perhaps they got lost when customs opened up the box and inspected the contents?). Careful inspection of the Science History Institute’s images of this instrument reveals that the colorimeter came with a 420/515 nm and 540/600 nm filters. The slot holder in the back has 6 slots suggesting that this instrument may have originally came with more filters which have no doubt been last over the years.

Figure 7 – The rear filter holder of the Evelyn colorimeter

Based on the wear pattern on the back of the instrument, it is pretty clear that some filters (or at least specific filter slots) were used more than others. Each filter set comes fitted with two glass filters (such as the 660 nm filter seen below in Figure 8) which serve to filter the light from the source to a narrower set of wavelengths pass through the sample and reaching the detector.

Figure 8 – The 660/690 nm filter that came with my slightly used Evelyn Colorimeter

Opening the front panel, which has a very satisfying feel to pulling on the Bakelite handle, reveals the colorimeter´s internal components: a detector, a sample holder, the filter holder, and the light source (Figure 9). To my surprise I actually found an extra bulb in the internal compartment!

Figure 9 – The internals of the Evelyn Colorimeter include a detector, sample holder, and light source. Note the extra bulb holder assembly (complete with broken bulb) and an extra bulb in the holder at the right. White residue and damage to the bottom wood panel are apparent.

On the inside of the door, this is a pair of instructions (Figure 10) for the operation of the colorimeter. The paper is old and very discolored but otherwise intact. The piece of plastic material covering this paper has become very brittle with age. Removing the pins such that I can remove the paper and restore the wood underneath is going to be a chore.

Figure 10 – A scan of the original instructions for the Evelyn Photoelectric Colorimeter

Restoration plans

Over the coming weeks, I plan on restoring this beautiful piece of history to its former glory. I’ll be quite curious to see if I can safely remove the grime and repair some of the superficial damage that this instrument has endured over the decades.


Evelyn, K. A. (1936) ‘a Stabilized Photoelectric Colorimeter With Light Filters’, Journal of Biological Chemistry, 115(1), pp. 63–75. doi: 10.1016/s0021-9258(18)74751-0.


The never ending pandemic

So after more than a year of life with the SARS-CoV-2 pandemic, I’m starting to wonder if this will ever actually end. I’ve been so busy adapting my classes and trying to minimize the damage done by in silico education that I’ve hardly had time to tend to my other duties such as writing up results for publication. All I want to do is get back to the lab.

The hardest part of this ordeal has been trying to maintain some semblance of academic excellence although I have some serious concerns about the validity of the academic work done, particularly at home exams, administered during lock down. One of the key lessons that I’ve learned is that an educator can really only count on their own abilities and cunning to see them through challenges. I am not sure that I can manage another year like this, with the ground constantly shifting beneath my feet.

Wow! So I finished my Ph.D?! Whoopdy-effing do.

I finished my doctorate last spring and have kept it on the down-low regarding advertising that fact. While I occasionally use the fact that I´ve got a Ph.D. to poke fun at myself when I mess up in front of students or use my powers of deductive reasoning to make very obvious statements, I do not see the point in “celebrating” this academic accomplishment. I´ve had a few returning students come up to me and ask if I´ve finished my Ph.D. yet which is followed by the obvious question: so can I call you “Doctor Scully”?. My reply to this is usually as follows:

Absolutely Fucking Not Boiler Room GIF - AbsolutelyFuckingNot BoilerRoom WolfOfWallStreet GIFs

That said, when I finish my next doctorate, I wouldn’t mind being called “doctor-doctor” on account of how ridiculous it sounds.

I´ve been admonished my friends, family, and co-workers for my constant underplaying of this ‘accomplishment’ (this has actually been a recurring theme throughout my life). And I get it! Well, sort of. I suppose some people are defensive and want to feel like their own academic accomplishments matter and mean something or they want to see people take credit for the hard work and so on and so forth. To each their own, I guess.

In my mind, having a doctorate means that I know stuff and have learned how to do stuff good but those things are not exclusive to Ph.D. holders. I´ve met dozens of highly competent and skilled people that are dedicated professionals that lack ‘credentials’. I´ve learned many of the skills vital to finish my Ph.D. from people that only have associates degrees or bachelor’s degrees. If it wasn´t for people taking the time to teach me real skills (like troubleshooting problems or not letting bureaucratic bullshit get to so you don’t have a brain aneurysm), I probably wouldn’t have made it through university let alone managed to become a bench scientist. I suppose the reality of the situation is, I was already a practicing scientist responsible for supervising the research work of students before having a Ph.D. so I didn’t really experience much of a bump in my abilities just by virtue of completing a Ph.D. so what´s the big deal?

I think my attitude on the subject goes back to how I was brought up. My father had a Ph.D. and he would never allow people to call him ‘Dr. Scully’. I suppose that makes sense given his profession (he was a clinical psychologist working with young kids). Why build barriers between you and the people that you´re trying to help? That just creates an unnecessary hurdle that you have to unpack later; that´s counterproductive A.F. especially when you are charging by the hour for your psychological services! He spoke poorly of his work colleagues that pulled the ‘doctor card’ when introducing themselves and I totally get that.

I think another critical element in this little attitude of mine was my maternal grandfather; he was a highly skilled professional that was always curious and pushing himself to learn new things. He could pick up a new interest and just run with it. He did not complete any formal schooling beyond high school (he got drafted while he was in college because he was a mediocre student) and that didn’t stop him from mastering new skills throughout his entire life and his careers.

When I was in university (the first time), I took a course in analytical chemistry. The guy teaching the course was only a few years older than most of us and he told us to call him by his first name. It was the early 2000s and a lot of the up-and-coming academics were much more chill about their credentials than the old timers. I swung by his office one day to ask him a question about something or other. He was chatting with an older-looking person but he flagged me in and answered my question. I said, “thanks Dan, I appreciate it” and turned to walk away when the old fossil stands up and stops me with a firm, “HEY!” and proceeds to put me in my place. “You address him as DOCTOR or PROFESSOR!”. I was horrified and had no idea what was happening. I was just a 19 or 20 year old kid and I had seldom been dressed down by an authority figure (it turns out that he was the department chairperson and had a bit of a think for old-school formalities).

To top it off, I moved to Iceland when I was in my early 20s. No one uses formal titles like ‘mister’ or ‘doctor’ or whatever. Everyone is on a first name basis here regardless of social standing or professional status. It took some getting used to at first but ultimately I think it creates a more open and friendly atmosphere so we can get to the business of discussion ideas rather than wasting breathe on such nonsense. I´ve read stories about how overly formal societies (such as Japan) leads to situations where people are afraid to point out the errors of their superiors which can have catastrophic consequences.

TL;DR: don´t call me “Doctor” Scully.

Örveruvistfræði Norðurslóða

An article regarding this year’s Microbial Ecology summer course.

Rannsóknastöðin Rif — Rif research

Dagana 22. til 24. júní s.l. heimsótti okkur stór hópur í tengslum við námskeiðið Örveruvistfræði Norðurslóða sem haldið er af Háskólanum á Akureyri í samstarfi við Háskólann í Reading, Bretlandi.  Í ár komu jafnframt nemendur frá Háskólanum í Massachusetts, Dartmouth og Háskólanum í Medellín í Kólumbíu. Nemendahópurinn taldi í heildina 29 manns og var honum stýrt af 16 manna teymi kennara og starfsmanna.  Það var því ansi mikið um að vera á Raufarhöfn þessa daga en hópurinn hafði bækistöð annars vegar í Hreiðrinu og hins vegar í Grunnskólanum.

Námskeiðið samanstóð af vettvangsferð, rannsóknarstofuvinnu, fyrirlestrum og verkefnavinnu tengdri náttúrulegri örverubíótu Norðurslóða. Í ár voru sérstaklega teknar fyrir örveruvistgerðir á Melrakkasléttu, í Öxarfirði og Jökulsárgljúfri ásamt fleiri stöðum.  Meðal örveruvistkerfa sem könnuð voru beint eða óbeint má nefna ýmis jaðarvistkerfi á borð við jökulís, hafís, súra hveri og basíska. Einnig var hugað að örverulífríki í jarðvegi móa og mela og í árvatni.

Markmið námskeiðsins eru þau helst…

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Hunting the Holuhraun Eruption in Norther Iceland

The Icelandic Metrological Office predicted an evening relatively free of cloud cover for the evening of September 12th so my wife and I jumped into the car and drive east hoping to find a clear vantage point to catch a glimpse of the lava field at Holuhraun. Additionally, a double CME had hit so at the very least there was a pretty good geomagnetic storm brewing overhead. With a good shot at catching a glimpse of the fissure eruption at Holuhraun and a near perfect shot at catching a good show of the Northern Lights, what was there to lose?

We drove around on a back road to Mývatn just off of Route 483 and found some truly stellar displays of the Northern Lights which had been visible as twilight fell.

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Not finding any evidence of the eruption being visible, we turned around and went south. Driving down route 483 towards the ominously red sky, we eventually landed at a farm in Svartárkot where we were greeted with a road closed sign.

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Not wanting to piss off the cops and risk getting arrested, we turned around and took a few photos on the way back.

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An abundance of visitors

The research group has been blessed with a sudden burst of visiting Erasmus students and a visiting professor from Germany! All in all, we’ve got a total of six (6!) Erasmus students working on a variety of projects involving thermophiles. With any luck we’ll be able to clear the back log of environmental enrichments from last summer’s bioprospecting while kicking the ball down the road on a number of research projects.

Here’s the breakdown:

  • Two undergrads from Finland working on the metabolism of Thermoanaerobacter strains (and a few Thermoanaerobacterium, Caloramator, and random other strains from class Clostridia)
  • One MSc student from Slovenia working on characterizing a handful of strains (that are likely new species) from our lab (including members of Paenibacillus, Thermoanaerobacter, and Thermoanaerobacterium) and bioethanol using lignocellulosic biomass with our crown king: Thermonaerobacter strain J1
  • Two BSc students from Montenegro working on characterizing some of our aerobic thermophiles from last summer and finalizing some enrichment cultures of thermophilic anaerobes
  • and one Lithuanian that will arrive in June (hopefully) that will likely end up working on something or other (TBD!)

Hopefully these guys and gals will have a blast while playing with these bugs.