Homeostasis

 My hikes, especially the grueling ones, double as medical monitoring. I regularly tell my doctor that I've just completed my stress test....An endurance hike, if I can survive that, my heart must be in pretty good shape!

In my experience, if my general health is good, incidental and focal illnesses are not as intense and resolve quicker.

Living things maintain homeostasis  We are assemblages of tiny bags of chemicals. Try throwing a bunch of chemicals in a bag and see how long the reactions last. Living thing evolved to maintain the chemical reactions we call life for a lifetime.

So, I put cold and warm tap water, and water from our tea kettle into plastic cups and dropped in Efferdent effervescent tablets. And I videoed the process. Guess the temperature sequence!

The cup on the left has the hot water and the one on the right has the cool water. The rate of the reaction is determined by the temperature. The last thing a living creature needs is to be dependent on temperature 

I wanted to know how well my body maintained its internal temperature so I taped a temperature and humidity sensor (Cloudcom A1 by ACInfinity) to my chest (the upper right circle below). The transmitter is in the lower left circle just above the bottom circle around my smartphone.

The data logger communicates with my phone via Bluetooth. Then I put on a t-shirt and my floppy hat and went on a 2,8 mile hike in the 103° F Chihuahuan desert.

The ACInfinity app collected the data and I imported it to my spreadsheet and charted it 

 As shown in the legend, the blue dots trace my body temperature (a little affected by the air temperature since the side of the sensor not against me was against tape, a t-shirt, and the outside world) and the red dots trace the humidity inside my T-shirt (mostly determined by my sweat.)

Two things in particular affected my body temperature: the cooling evaporation of my sweat and the blood which was being shunted to my skin to get rid of its heat (Despite America's song about the "Horse With No Name", I didn't turn brown....I turned red). There's a little temperature fluctuation in the chart but it's on the order of four degrees around 95°.  Looking at the histogram provided by the ACInfinity app, .....

my body temperature was between 93.9° and 97.2°. The mean was around 96° which is pretty close to my regular body temperature. (Yep. I'm cool.....at least my body temp. is. Average normal value for humans is 97.9° but that value varies considerably between 97 to 99° with older people being a little cooler and axial (armpit) temperatures being about a degree below oral temperatures.

Those low temperatures happened when I got back to my air conditioned house.

The humidity readings followed my sweating, which dropped pretty quickly when I started back and stepped into the shade of a pecan orchard  Notice that,  that jogged my temperature a bit but it stabilized quickly.

All in all, my body does pretty well maintaining an even body temperature.

Blood pressure is a different matter. My homeostasis in the area of blood pressure has been rather faulty most of my adult life. Both of my parents' families had a tendency towards hypertension. But there are drugs for that. 

One way you can explore bioIogical processes is in your own body. Home diagnostic equipment like blood pressure cuffs, thermometers, and even stethoscopes are not expensive. I tracked my temperature, blood pressure and pulse through a day and came up with these results 

Only that top blood pressure reading (systolic and diastolic) is in a clinically significant range and for my history it's still pretty good. 

I take most of my antihypertensive drugs soon after awakening, which explains why my blood pressure quickly dropped after the first reading  Otherwise, my pulse and temperature behave during the day. The mildly effortful task of cleaning out the refrigerator didn't even appreciably change the readings 

If you're curious about the "systolic" and "diastolic",  check your blood pressure sometime, at home or at one of those department store kiosks. The cuff will inflate around your arm (or some of the home units use a finger) and then start to deflate. At a point, you will feel your pulse..... that's your systolic pressure where your heart's strongest stroke is fighting the cuff. Then at another point the pulse will almost disappear because the cuff's pressure no longer blocks your circulation..... that's your diastolic. It's the pressure behind your heart's weaker stroke. If you have access to a stethoscope, you can hear this double stroke.

Medical diagnostics are a rich source of information for students of biology. They measure homeostasis. The "normal range" is the values your body tries to maintain. The temperature range of 97° to 99° F. Is the optimal range for the chemical reactions that keep you alive. 

What I call "endurance hikes" are exercises I do to push myself a little outside those limits to see if my body can effectively bring me back to optimal conditions 

Some of the processes of over-exertion simulate the more dangerous process of starvation. You have the resources to recover quickly but you don't access them quickly enough to maintain balance. I've made several endurance hikes while writing these blog. You can search for "endurance hike" using the blog's search box in the upper left 

In starvation, you first draw on the glycogen stores in your muscles and liver. You can do that for about a day. Longer, and you start burning up protein stores in muscles  Generally, you want to conserve  your muscle tissues while delivering enough glucose past your blood-brain barrier to fuel your brain. That's when you start drawing on fat deposits which deliver ketones which can easily cross over into your brain. 

On a long hard hike, it's not hard to catch the ammonia scent of proteins being burnt or the musty or fruity smell of ketones.

For extreme exertion, the primary factors you need to monitor are blood glucose (trail mixes that gives fast release sugars and slow release fats and proteins are actually good sources), hydration, and electrolytes (sodium, chloride, potassium, and calcium are the most important) Clarity of mind, muscle tone, and your own smell are good indicators but you should have planned stops to replenish and concentrate on how you feel 

Unfortunately, there are two ways that homeostasis can go wrong. It's easy enough to overdrive it if you're not paying attention and push yourself outside your limits. Or your homeostatic machine can be defective.

An example....I know several people with diabetes 

Glucose is the fuel that living things oxidize to get energy. They can't directly burn the sugar, of course, so there are involved chains if chemical reactions that gradually break the simple sugar down and store the energy produced in compounds like ATP that can release the stored energy as needed. But the toxic level of glucose in the blood is fairly low so glucose levels must be kept fairly tightly between toxic and starvation levels.

Human bodies maintain blood glucose levels using two negative feedback loops. Three systems sense glucose levels. The primary organ in the loop is the pancreas. It has alpha cells that sense when blood glucose is too low and release glucagon which signals the body to break down glycogen stored in muscle and liver tissue to release glucose. There are a couple other mechanisms to control glucose levels. The brain itself can detect glucose in the blood and modify the hunger response. Also the gut can produce a hormone, insulin that tells the pancreas to produce insulin. 

The pancreas also has beta cells that sense high levels of glucose and cause other cells in the pancreas (called "the Isles of Langerhans") to secrete a polypeptide, insulin, which triggers the reactions that polymerizes glucose to form fats in adipose tissues and glycogen in liver and muscle cells.

There are two forms of diabetes (at least). In one, type 1 diabetes, the body's immune response attacks the pancreas and kills the cells that produce insulin. Without insulin, there is no quick response to too much glucose in the blood. In the other, the cells that store glucose develop a tolerance to Insulin and doesn't react to take glucose out of the blood. That's type 2 diabetes. (There's also a third form of diabetes associated with pregnancy, gestational diabetes. There may be other, rarer forms).

Homeostasis, control of blood glucose levels doesn't work in people with diabetes, so they have to use artificial means. One friend has a pump that responds to an attached glucose sensor to deliver  synthetic insulin by injection. The older way to deal with type 1 diabetes was to frequently measure blood glucose from finger sticks to adjust dietary intake of carbohydrates.

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Another example of homeostasis gone wrong is fever. It's part of the general inflammatory response. If you turn your ankle or have some other joint problem or if a wound gets infected, you might notice that the area becomes warner to the touch. Microscopic pathogens also have "normal" temperature range and your body will try to make them hotter than is good for them. Unfortunately, the response over does it and let's your internal temperature get too high. That's when the behavioral side of homeostasis comes into effect and you start taking medicine and wiping your forehead with cool cloths to get your temperature down.

Homeostasis has to work at all levels for life to happen.

For instance, for the chemical processes that make up life, the human body needs to maintain a pH range between 7.35 and 7.45. There are several buffer systems in the blood to achieve that but the primary one is the bicarbonate-carbonic acid system. The carbon dioxide formed as a waste product of metabolism in the body is carried to the lungs dissolved in blood to be removed into the air. Carbon dioxide dissolved in water is carbonic acid. Along with the sodium ions, sodium bicarbonate is also present. It just so happens that the carbonic acid (an acid that can neutralize bases) and sodium bicarbonate (a base that can neutralize acids) form a chemical system that maintains it's environment between a pH of 7.35 and 7.45.

You can actually throw this buffer system off by breathing fast and hard (hyperventilating) and loading the blood stream with too much carbon dioxide. That causes respiratory acidosis, a condition that can cause severe side effects 

On the cellular level, there are proteins in cell walls that can move glucose into and out of cells but you need to have a certain amount in the cell to fuel the cell. Once the sugar is in, you don't want it to escape, so the first thing a cell does when processing sugar is to attach a phosphate group so that it can't leave 

On the organism level, both hormones and autonomic nerves play a part in homeostasis and not just with negative feedback loops. Positive feedback is also used 

One of the "feel good" hormones, oxytocin, plays a big part in childbirth. When the child's head presses up against the mother's cervix, it stimulates the production of oxytocin by the brain which, in turn, causes uterine contractions. That causes more pressure on the cervix until the baby is born and the process is shut down.

The process of blood clotting in a wound is also a positive feedback loop with the clotting factors increasing until bleeding stops.

Feedback loops operate to maintain balance on the ecosystem and even the global levels.

Predator-prey populations are classic. If there are too many predators, they eat too many prey. Then there's not enough food and some of the predators die until balance is restored. If there are too few predators, the prey overpopulate and reduce their food resources, which reduces the prey population and valance us restored.

Two major studies are the Isle Royale wolf-moose study

Wolves and Moose on Isle Royale

And the Yellowstone River wolf reintroduction study.

History of Wolves in Yellowstone

Do plants demonstrate homeostasis? Certainly.

An interesting demonstration tracks the state of stomata (leaf pores) in plant leaves.

Plants take in one of their primary nutrients, carbon dioxide, through these pores. They use carbon dioxide to build sugar via photosynthesis. Then they use the sugar the same way we do, as fuel. The process also needs water, which most plants take up through their roots. But evaporation of water through stomata produces a negative pressure that draws water up into the plant.

Stomata open and close to take up or conserve gases (carbon dioxide or waste oxygen) or water vapor (and keep in mind the cycle in which plants "breathe" in carbon dioxide and ",breathe" out oxygen while animals breathe in oxygen and breathe out carbon dioxide...... it's important).

You can observe stomata by taking a cast of a leaf using clear nail polish  You need the nail polish, clear tape, and a microscope slide.

Lightly paint a strip of polish over the leaf. There is usually more stomata on the underside of leaves. Give if 15 minutes to dry. I used Sally Hansen's Diamond and waited 30 minutes once. The cast came out perfectly. Stick a piece of clear tape over the polish. When you peel the tape off, the polish will come with it. Stick the tape to the microscope slide. 

Keep in mind that you aren't looking at the leaf. You're examining an impression of the leaf surface. The reason for looking at the cast is that you can't see through the leaf with a light microscope 

Here are my subjects.

Right; pistachio (Pistacia vera, probably)

Left: ash (my guess velvet ash: Fraxinus velutina)

Pistachio leaf

Here's a cast I took during the hot part of the day

And one I took at 9:00 PM.

Notice that the pores seem to be more open at night. They are. The plant is trying to conserve water and carbon dioxide during the hot hours of the day, but it has to get rid of oxygen and extra water so it waits until night to do that.

Top level responses like behavior play a part in homeostasis. Abraham Maslow organized needs by order of urgency. We barely consider higher level needs if lower level needs aren't met. If you're hungry, you don't worry too much about social status  Here's his pyramid.

Maslow's Hierarchy of Needs

From Wikipedia. Author: Factory Joe. (6/29/2009)

And not all of our behavior is choice. Part of our neuronal machine is the autonomic nervous system. It's "autonomic" because it's automatic. It takes care of things like breathing, sweating, digestion....things you don't want to tell your body to do everytime.

There are two parts to the autonomic system: the sympathetic nervous system and the parasympathetic system 

If you're surprised by something, whether it's dangerous or not, your body goes on alert by triggering the sympathetic system  It speeds up you're heart and lungs to get oxygen and fuel to your cells. It also slows down your digestion (this is no time for stomach issues!) and dilates your pupils to get more light to your eyes. It also stimulates your adrenal glands to release epinephrine which tells your metabolism to go into catabolic overdrive so that cells will break down stores of glucose for quick energy.

It's called "fight or flight response" because it's what it makes you want to do.

There's an opposite reaction governed by the parasympathetic system when things are nice and calm and you can conserve energy. Digestion ramps up to set up stores of fuel. Most other functions slow down and you get to "rest and digest" ( that's what the parasympathetic response is often called. Sometimes it's called "tend and befriend"). When things are going well, you might get a dose of oxytocin, the "feel good" hormone.

When the sympathetic system goes on the fritz, it might result in a reaction called Generalized Anxiety Reaction. If you see someone in the middle of one, don't tell them to calm down, they can't. And it is often described as the feeling that you're going to die. Usually they don't (I've been there, by the way. I can vouch for it ) Just stay with them. Make sure they're in a safe space. Offer them cool water. Be supportive and remind them to breathe deeply and slowly. Ask them what they need 

An attack usually doesn't require hospitalization but if it lasts more than a few minutes, it might be something else so don't panic and call an emergency number.

There is another reaction called "homeostatic emotion". If you've ever been so hungry, thirsty, or oxygen deprived that urgently have to do something about it you've experienced it 

Every morning, your body ramps up for business. You may have notice when you were sick or injured that inflammations get worse later in the day. That's because the body dumps cortisols into the bloodstream early to get inflammations out of the way at the start of the day. Also, the reason you don't soil your bed in your sleep is that, when the parasympathetic nervous system puts you in rest mode, it clamps off exits from the body. Those open up when the day starts.

The sympathetic reaction perhaps should be called "fight, flight, or get busy". Exercise routines tell the body when to fire up the sympathetic system. When I was in college, I exercised religiously but I soon learned that if I exerted myself during an epidemic, I would catch whatever was going around.

I have an overactive immune system. As a consequence, I rarely ever have an infection and when I do, it lasts a few hours or maybe a day, but if it triggers an inflammation, I was in for it. Bronchitis, gastroenteritis, and iritis have been the babes of my existence all my life. As I've aged, joint problems have joined the trio 

But as I've aged, I've also learned ways to navigate my inflammatory problems. For instance, knowing that exertion reduces my body defenses, I use that to modulate them.

Homeostasis is a constant thread in biology from biochemistry to planetary ecology. It will appear over and over 

But if you don't become interested in biology as a long time study, you should learn how to balance your internal environment.

I haven't come close to completely covering the topic. I've just recounted my adventures. If you really want to learn about homeostasis, here are my sources:

Kahn Academy. They have whole sections on biology and if you just want to study homeostasis, they have a search bar that you can type "homeostasis" into. Lectures, articles, hands-on experiments, tests, they're all there 

CK12 Biology for High School. Multiple contributors

CK12 Biology for High School

Many healthcare providers have patient portals that allow patients to look at their own records. I use those a lot. 

And I look up normal ranges of medical tests in my copy of the Merck Manual. They're also on various websites.

 

What's Little Dry Creek made of?

Everything recycles on the Earth. Air, water, rock are are all conditioned, modified, processed, and returned to the surface fresh and ready for reuse. My vote for the "lifeblood of the planet" would be water. It's hard to imagine a planet without water with any life above simple, single cell beings. Water perculates underground to create caves and deposit metal ores in fissures. Water not only washes the ground as rain, but rain aerates streams with life giving oxygen. It's weird properties causes it to float as it freezes, giving fish and other creatures beneath it protection against the outside world. 

Water vapor is a greenhouse gas that helps Earth regulate it's temperature. If you live in a temperate climate, you might notice that cloudless winter nights can be brutal. Clouds generally moderate cold nights by holding daytime heat nearer the ground.

The primary component of Little Dry Creek is water. It's may be a very familiar substance, but it's also very strange. As I mentioned above, unlike most substances, it's solid form is less dense than it's liquid form so that ice floats on water. It's a weak acid and base. A liter of water will ionize to contain 0.0000001 liters of hydrogen ions (making it slightly acid) and 0.0000001 hydronium ions (making it slightly basic). The water (dihydrogen oxide) molecule is polar, the electron hungry oxygen atom pulls the hydrogen atoms electrons away making the two hydrogens positively charged while the oxygen is negatively charged. These charges rip ionic substances apart making water the "universal solvent". Water is good at moving other substances around.

Little Dry Creek is fed by runoff and the Dawson aquifer. As water falls on the ground and pavement around Centennial, Colorado it has to go somewhere. The two main "drainages ditches" are Little Dry Creek and Willow Creek.  It can also deep into the porous sandstone of the Dawson, Arapahoe, and Denver formations in the Denver Basin and pour out at the many springs in the area. One is just east of Yosemite Street.

The water from the aquifer is well filtered and fairly clean but runoff from the surrounding area carries substances into the stream. Being interested in whether agricultural products were being washed into the creek in the Walnut Hills area, I wanted to test for nitrogenous materials in the water. An aquarium test kit checks for pH (acidity), ammonium, nitrate, and nitrite - perfect for my interests.

I was also interested in the dissolved metal content and decided to perform a chromatographic analysis.

I sampled the creek at three points: as it emerges from the spring, just east of Uinta Street, and at the small cascade east of Spruce Street. I also measured the air and water temperatures.

Using Google Sheets, a spreadsheet that stores the documents I created online in secure memory set aside for me by Google, I recorded the results of the analyses.

The air temperature was right around what would be considered room temperature or a little cooler but the water was frigid, just a few degrees about freezing. Not unexpectedly, it was cold as it emerges from the aquifer (3.5°) and it warmed up to 6.6° about a half a mile away after it had picked up some runoff. But it was actually colder a little further down. This was where it picked up the intermittent stream from Fiddler's Green, which ran a good bit of it's course underground.

The table above gives parts per million amounts of various substances in Little Dry Creek water at (from top to bottom) sites 1, 2, and 3. The bottom row is our home tap water.

What initially drew my interest to chemistry were two things - fire and color. On the color side we're analytical indicators, solutions that changes color in the presence of certain materials. The picture at the top of this blog shows the pH test for water from site 1 (the spring). (Ain't it perty?)

There are indicators for a lot of substances. Early on, indicators were primarily used only for qualitative analyses. In other words, they could only be used to determine the presence or absence of a substance, not how much there was. But as methods were developed to measure the degree of color change in a solution, quantitative methods also developed to indicate how much of substances were in a solution.

Including high school and college chemistry labs, I would imagine that pH is the most common chemical characteristic tested for. It's an indication of the acidity or alkalinity of a solution.

I used the Top Fin aquarium test kit to test for pH, ammonia content, nitrate, and nitrite. I could not find the actual ingredients used but they look (from the color reactions) pretty much like most of the other kits.

So, what is pH?

Chemists use p functions to express concentrations of substances in solutions, especially substances that exist in tiny amounts in solutions. Specifically, pH describes the concentration of hydrogen ions in solutions of weak acid or dilute strong acids. Concentration is expressed in moles of dissolved substance (solute) per liter of solvent. A mole is 6.02214076×10²³  particles (it's not as complicated as it looks. You add up the atomic masses of all the different atoms in a substance - the atomic mass of sodium is 23 and that of chlorine is 35 so the sum is 58 - and a mole is that number of grams. A mole of sodium chloride - table salt - weighs 58 grams.) So the pH of a solution is the number of moles of hydrogen ions in a liter of solution.

Take water for example. It is both a weak acid and a weak base. It ionizes to form hydrogen ions and hydroxide ions in equal amounts. It's a weak acid because a liter of pure water has only 0.0000001 moles of free hydrogen ions in it. (By contrast, hydrochloric acid is a strong acid because, in a water solution, all the molecules come apart to form hydrogen and chloride ions.) 0.0000001 is an awkward number so chemists use the negative logarithm (to base 10). The logarithm of 0.0000001 is -7, so the negative logarithm is 7.

Water is special since it dissociates into equal numbers of hydrogen and hydroxide ions - half way between acids and bases. Acid-wise, pure water is neutral. Water is both a weak acid and a weak base. A characteristic of mixtures of weak acids and bases is that they resist becoming more acid or basic. If an acid is added to water, the hydroxide ions neutralize some of it to form more water (H + OH = H2O). If a base is added to water, the hydrogen ions will tend to neutralize the extra hydroxide ions. Such a mixture of weak acid and base is called a buffer. So it takes a lot of acidic leaves or carbon dioxide from the air to acidify water to a level that's dangerous for aquatic life. Similarly, it takes a lot of limestone to raise the alkalinity of water to a dangerous degree. Mind you, there are lakes like Ijen in Indonesia, that are so acid that the water will eat the skin right off your body. Highly acid lakes are usually volcanic or has water that has leached a lot of acid from mine tailings.

Anyway, safe water should be nearly neutral. In other words, it should have a pH close to 7.

Judging from the color change for the pH indicator (red fir acid to green for bases), I would guess that the indicator I used is a mixture of bromothymol blue and cresol red. The cresol red is red at pHs around 5 and yellow above 6. Bromothymol blue is colorless below pH 6.5 and turns progressively bluer above 6.5.

Most wide range pH indicators are such mixtures. Anthrocyanines that give flowers and fall leaves red, blue, and purple colors are an exception that goes through color shifts over a wide range of pHs. (see http://adventuringbcc.blogspot.com/2022/02/eat-your-beetsthen-use-juice-to-test-ph.html).

That green color in the picture at the top of this blog means that the water from Little Dry Creek has a pH of around 6.5 and it's consistent throughout Walnut Hills. A pH less than 7 is acid but 6.5 isn't very acid and is well within a safe range for aquatic life. Notice that our tap water is a little basic (7.5). The creek water is a little acid because leaves fall into it and the tannic acid leaches out. Also, carbon dioxide from the air dissolves in water to form weak carbonic acid. Cold water will hold more gas in solution than warm water. Little Dry Creek was very cold, at least when I fell in!

Ammonia is a stable nitrogen and hydrogen compound. A gas at commonly experienced temperature and pressure, it's also frequently given off by cleaning fluids and has a sweetish, biting, rather repulsive odor. (Ammonia water, a solution of ammonia gas in water, is a common cleaning fluid.)

It's common in nature as a byproduct of decay. Any water that has or has had living organisms in it can be expected to have a little ammonia. There's not usually enough to smell. A stream can be loaded if agricultural chemicals like fertilizers or raw sewage is dumped in.

A common test for ammonia uses a phenolic compound to react with ammonia to form an indole compound that is bright blue. The Top Fin test has two solutions. The first contains the phenol compound, sodium salicylate (related to the salicylic acid in willows and other plants, methyl salicylates also known as wintergreen oil, and acetylsalicylic acid or aspirin). The second solution contains sodium hydroxide (which adjusts the pH of the solution), sodium hypochlorite (which chlorinated the product), and sodium nitroferricyanide (which catalyzes the reaction). The combined solutions without the ammonia is yellow but if the indole forms, the yellow color mixes with the blue dye to form a green solution, the more ammonia, the darker green.

The spring water contained 2 parts per million ammonia. The EPA maximum standard for freshwater is 17 milligrams of ammonia per liter of water (that's 17 ppm). The other two sites showed 0.25 ppm ammonia. Interestingly, our drinking water has more dissolved ammonia (0.5 ppm) than the creek. It's not surprising that the "pure" spring water has more ammonia. It's a gas and colder water under pressure can hold more devolved gas than the water in an aquifer. The ammonia is released as it flows in the open stream.

Nitrates and nitrites are also common nitrogenous compounds found both in nature and in industrial processes. They are anions of nitric and nitrous acids (respectively) and their salts. Nitrates are also artificial fertilizers that are readily taken up by plants, especially as the ammonium salt, ammonium nitrate. In lakes and streams, they can lead to overpopulation of algaes. The Top Fin kit has tests for both.

Before I get into the Griess reaction, which is commonly used to test for nitrites, I need to explain "aromatics". When I use that word, most people are going to think "something that smells nice." Chemists think something else. The two meanings do overlap. Many nice smelling (and colorful!) Substances are also aromatic compounds, but there are aromatics (like the number one aromatic, benzene) that most people would say smells unpleasant.

Aromatics have this ring structure somewhere in their molecule.

That's benzene, six carbon atoms (the six gray balls) bonded to six hydrogen atoms (the white balls). Other atoms and collections of atoms can take the place of one or more hydrogen.

The Griess reaction is used to being and two of these rings together.

Start with an aromatic compounds with an amide group replacing one of the hydrogens. In our case, it's probably sulfanilamide.

The nitrogen with two hydrogens at the bottom is the amide group we want to target. A nitrite ion will knock the two hydrogens of the amide group off to form a diazo group (just two nitrogens) and the whole molecule becomes a positively charged ion waiting to react with something....it likes the carbons in an aromatic ring.

In the Griess test, we want an end result that's brightly colored....an azo dye. One common aromatic reactant, and probably the one in the Top Fin kit, is N-(1-naphthyl)ethylenediamine. It's a big word, but the stick diagram is rather pretty.

The carbon just opposite the tail on this molecule.... that's where the diazo group latches on. The result is this dye.

It's purple. The more nitrite is present, the more of the two aromatic compounds get stuck together and the more purple the solution becomes.

What about the water in Little Dry Creek (and in my drinking water)? There was no nitrite in our tap water and the creek had a tiny, but consistent amount at all three sites, 0.1 parts per million, which is about 0.1 milligram in a liter of creek water. The Environmental Protection Agency's maximum contaminant level goal for nitrites in drinking water is 3.3 mg/L.

The nitrate test seems to be the same Griess reaction used for the nitrite test except the nitrates gave to be reduced to nitrite (with concentrated hydrochloric acid and a witches' brew of other substances). It used sulfanilamide but I couldn't find what it was reacted with to give a red color. 

The test didn't indicate any nitrate in our drinking water or at the spring but the creek had picked up 5 parts per million of nitrate by site 2 and that concentration continued at least to site 3. 

EPA maximum contaminant goal for nitrate is pretty high, 44 mg/L, so the creek is okay for nitrates.

Eat your beets...then use the juice to test pH!

As a child, Two things attracted me to chemistry...colorful reactions and fire/explosions. My favorite gifts were science kits and at the top of the list was a chemistry set.

As I got older, I was delighted to find that you didn't need a chemistry set to have fun with chemistry. Everything is composed of chemicals! Check out these colorful reactions.

The big depression in the spot plate is filled with the juice from some beets my son cooked the night before, butter and all! The upper depression has a solution of baking soda. The one below it has tap water. The bottom depression has some rice vinegar in it. The color is from beet juice.

The reason the colors are different is pH. So, what is pH?

p functions (there are many that are used in chemistry) are ways of reporting concentration, especially concentrations of ions in solutions. pH, specifically, tells the concentration of hydrogen ions (that's what the H stands for) in a solution. Acids are substances that place hydrogen ions into a solution; bases are substances that take them out, usually putting hydroxide ions in instead. Concentrated acids and bases are very reactive.

I used to sell car batteries. The sulfuric acid in car batteries will dissolve cotton and turn your skin into parchment. I couldn't keep blue jeans and my knuckles would crack to the bone. A strong base like lye will also take your skin off. Of course, sometimes you want a concentrated acid or base. Strong lye solutions are used in the manufacturing of soap.

The hydrogen ion concentration can range from 0.1 mole per liter in a very concentrated acid to 0.00000000000001 moles per liter in a very basic solution. These numbers are disturbing, but the negative logarithms (base 10) are 1 and 14. That's what a pH is, a negative logarithm, and that's why they're used.

The logarithm (base 10) of 10 is 1, 100 is 2, 1000 is 3, and so on. See? The number of zeros tells you the logarithm. Between each multiple of 10, the logarithms will be between whole numbers. For fractions, the logarithm of 1/10 is -1, 1/100 is -2, 1/1000 is -3, and so on. p function values are negative logarithms so that small numbers will be positive values.

Pure water at room temperature and atmospheric pressure at sea level has a pH of 7 and that is considered neutral because there are the same number of hydrogen ions as there are hydroxide ions. That makes sense because each water molecule splits into a hydrogen ion (actually, each hydrogen ion binds with a water molecule to form a hydronium ion) and a hydrogen ion.

It's nice to have a way to test for acids and bases. Enter beet juice...

Many plants (not just beets) have compounds called anthocyanins. In fact, many of the reds and purples of autumn are from anthocyanins in leaves of trees that are masked during the spring and summer by chlorophyll. Blue and red flowers are often colored by anthocyanins.

But why do they change colors with acids and bases?

Anthocyanins are acids that can lose hydrogen atoms to form basic ions. The neutral molecule and the ion have different colors. In the case of beet juice, it's red when there's a lot of hydrogen ions (in an acid) and yellow when most of the hydrogen is tied up (in a base). Beet juice turns from red to blue to yellow as it becomes less acid and more basic. The yellow color only shows in extremely basic solutions...pH 11 and higher. The sodium bicarbonate solution in the photograph is only weakly basic.

I used to take different colored flowers and hang them above ammonia cleaning fluid, a base, or hydrochloric acid, an acid. The vapors the fluids give off are also basic and acidic. You should try it. The color changes are dramatic.

I would also make violet syrup. If you can find a big patch of violets (don't destroy a whole patch of flowers just to make syrup), pack a Mason jar full and pour hot simple syrup over them (half water and half sugar by volume). Stretch some plastic wrap quickly over the mouth of the jar until it cools (you don't want to lose any of the violet flavor), and then screw the lid on for a day. You'll end up with a dirty blue liquid. That's the basic color. Now add just enough lemon juice to turn the fluid a beautiful magenta. That's the acidic color.  You have a tasty, violet flavored syrup. I think it tastes like wildflower honey.