The Clear Science staff recently read a couple of articles about researching a scientific basis for the widely-believed health benefits of cranberry juice. Cranberry juice is renowned for preventing urinary tract infections (UTIs), and there is evidence that it hinders E. coli attachment to cells in the urinary tract. Also, molecules found in cranberries can chelate or bind iron atoms. They do this because they have a lot of phenolic OH group on them. Lone pairs on the oxygens chelate positive metals (chelate means “hold like a claw”). This could remove extra iron from your system.
But these theories are not without counter-evidence. The residence time of cranberry components in your system after you drink them is low. Some argue that to make a real difference, they would have to stick around much longer, or you would have to drink a lot of juice.
We called the voltaic pile the first modern battery, because some believe that objects discovered in the 1930s (that date to the biblical era) were early batteries, called “Baghdad batteries.” These have iron rods surrounded by copper tubes, and the two metals could be separated by an electrolyte. This is the basic construction of the electrochemical cell we described earlier, with iron replacing zinc.
However, it is unknown if these objects were used this way, or for some other purpose that has not been thought of. This type of battery would have a very low potential (about 0.44 volts) and would not have a lot of power. (The voltage of the cell is the difference between the individual electrode potentials.)
By connecting zinc and copper discs separated by brine-soaked cloth, a zinc-hydrogen cell in made. Alessandro Volta studied the effect produced when metals were connected this way. One of his papers (from 1769) was called De vi attractiva ignis electrici or “On the attractive force of electric fire.” In the 1800s the concept of a battery began to be developed. By connecting several cells, stacking them, a higher voltage is produced. The word voltage comes from his name.
The Clear Science Staff got an email from a producer for National Geographic a few weeks ago, and they wanted to record us explaining how a citrus battery works. (That’s us in the video BTW.) It’s for a science/comedy show that comes out next year called Duck Quacks Don’t Echo.
You put nails made out of two different metals into some acidic fruit, like an orange. If one is zinc and one is copper, you essentially make a zinc-hydrogen cell.
The battery half-reactions are 1) zinc electrodissolution (anode):
Zn → Zn2+ + 2e-
and 2) hydrogen formation (cathode):
2H+ + 2e- → H2
The zinc electrodissolution obviously happens on the surface of the zinc nail, and releases electrons. These electrons are at a low potential and want to flow to someplace at high potential. The hydrogen formation has a higher potential, and occurs when the protons (H+) in the fruit acid meet the electrons at the copper nail to form hydrogen gas (H2).
So if the two nails are connected, electrons will want to flow from the zinc nail to the copper nail. In between these two nails you place something like a cell phone. Flowing electrons are electricity, and so when they flow through the phone charger it’s electricity to charge the phone. This is how batteries work.
The Clear Science staff has been busy with battery science lately, so we haven’t had a chance to post. Perhaps talking a bit about batteries would be a good way to fill the void.
Did you know sometimes batteries are actually made of other batteries? If you cut open a 6-volt lantern battery, as they do in this video, you will find 4 smaller batteries inside. Usually these are 4 F-cell batteries (as in the video). Sometimes it is 4 D-cell batteries. An F-cell is like a D-cell but taller.
F- and D-cell batteries each have ~1.5 V potential. So that’s how they get 6 V:
For our posts on what smells are, the Clear Science staff used a strawberry as the example because it’s well known what chemicals are in a strawberry and because we like them. But did you know: not everyone is a fan?
A list of the volatile organic compounds found in strawberries has about two dozen chemicals on it. Examples are methyl butyrate, octyl acetate, hexanol, etc.
Since these chemicals are volatile, they are always evaporating a little bit, and you smell them in the air. In different kinds of strawberries, the amounts change a little bit. The smells we can sense (in strawberries and everything else) are the result of complex mixtures of volatiles, like this one.
During photosynthesis the enzyme RuBisCO does the work of reducing carbon dioxide from the atmosphere. It is reacted with a molecule of ribulose-1,5-bisphosphate anion, which has a 5-carbon backbone. The resulting unstable 6-carbon compound immediately breaks down into two molecules of glycerate 3-phosphate, which is 3-carbons.
This happens during the Calvin Cycle (or the light-independent reactions or dark reactions). All the carbon chains you love, like plants, food, fuel, cats, dogs, and you, started getting linked together this way.