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.

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.

As the Clear Science Labs are based in the United States, we’ll be away for Thanksgiving for the rest of the week. We’re thankful for volts and amps and watts this year. How about you?

As the Clear Science Labs are based in the United States, we’ll be away for Thanksgiving for the rest of the week. We’re thankful for volts and amps and watts this year. How about you?

(Source: vintageedition, via freshphotons)

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.)

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.
This is essentially the same idea as a citrus battery, where instead of brine you have citrus juice.

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.

This is essentially the same idea as a citrus battery, where instead of brine you have citrus juice.

Batteries are electrochemical cells. Electrochemical cells are two electrochemical half-reactions coupled to each other. A zinc-hydrogen battery, which is what you make if you make a citrus battery, has:
a hydrogen-forming half-reaction that happens at 0 V
a zinc-dissolving half-reaction that happens at -0.76 V
In reality, half-reactions cannot exist independently. They must always be coupled to make a cell. This is because otherwise you have electrons without a home. 

Batteries are electrochemical cells. Electrochemical cells are two electrochemical half-reactions coupled to each other. A zinc-hydrogen battery, which is what you make if you make a citrus battery, has:

  1. a hydrogen-forming half-reaction that happens at 0 V
  2. a zinc-dissolving half-reaction that happens at -0.76 V

In reality, half-reactions cannot exist independently. They must always be coupled to make a cell. This is because otherwise you have electrons without a home. 

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:

  • 1.5 V x 4 = 6 V 

constant--randomness asked: regarding viewsofalien's question: you wrote that "Visible light tends to get scattered and blocked by crystallinity, i.e. regularly repeating atoms" -- what about diamonds, quartz... all kinds of jewels/gems? they are all crystalline and highly transparent.

Excellent point username: constantrandomness (and totally non-random!).

Our answer was pretty incomplete, because crystallinity will only scatter light if it has some order that is about as big as the wavelength of the light in question. Other factors cause opacity, such as the number of interfaces the light has to cross. In this example from a while back, the Clear Science staff used this to explain why snow is opaque. But instead of individual snowflakes, the grain boundaries in crystalline substances can also act this way. To add more complication, substances can also absorb light instead of transmitting it.

So it’s really an semi-unsatisfying answer: “anything visible light can’t go through is opaque.” And crystallinity and interfaces can play a part in that.

viewsofalien asked: What makes different things transparent, translucent and opaque?

Well, username: viewsofalien, it all has to do with visible light since that’s what our eyes “see.” Does an object block visible light, smear it, or let it straight through? That will determine it. Visible light tends to get scattered and blocked by crystallinity, i.e. regularly repeating atoms. “Amorphous” materials like glass tend to let light go right through! 

emgremlyn asked: Hi I am a new science tumblr and I need some one to notice my blog. I love your blog. If you could help my blog get people to notice me it would mean a lot. Thank you soooo much.

Hi username: emgremlyn, why not. The Clear Science staff liked the article you posted about 3D printing organs.