manwithoutborders:

clearscience:

A battery scientist’s trivial dilemma
You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)
Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:
3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO
The 303/357 is a silver oxide battery having the overall reaction:
Zn + Ag2O = 2 Ag + ZnO
They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

Being a chemist, I’m more loyal to representing mixed oxides in the longhand format, MnO+Mn2O3. I don’t think the reaction in a battery is vigorous enough to produce “actual” Mn3O4. Is it common for battery scientist to use Mn3O4 over Mn2O3 as the product, I’m going to have to tear open a dead battery and check this on XRD. 

It’s a good point. However, if the battery is discharged at a sufficiently slow rate (20 hours or slower) you do observe the well-formed spinel structure of Mn3O4. Opening the battery and using a standard XRD will result in a collection of products that are difficult to distinguish. By using a synchrotron beam to do diffraction through the battery without opening it, a good Mn3O4 structure is observed. The Clear Science staff will have a paper out about this soon … our preliminary paper on the technique is here.
We aren’t the first people to identify Mn3O4 as the slow-rate product. The Handbook of Batteries gives the same reaction as we have written above. (Wikipedia lists a different reaction, which is not well supported by the literature.)

manwithoutborders:

clearscience:

A battery scientist’s trivial dilemma

You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)

Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:

  • 3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO

The 303/357 is a silver oxide battery having the overall reaction:

  • Zn + Ag2O = 2 Ag + ZnO

They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

Being a chemist, I’m more loyal to representing mixed oxides in the longhand format, MnO+Mn2O3. I don’t think the reaction in a battery is vigorous enough to produce “actual” Mn3O4. Is it common for battery scientist to use Mn3O4 over Mn2O3 as the product, I’m going to have to tear open a dead battery and check this on XRD. 

It’s a good point. However, if the battery is discharged at a sufficiently slow rate (20 hours or slower) you do observe the well-formed spinel structure of Mn3O4Opening the battery and using a standard XRD will result in a collection of products that are difficult to distinguish. By using a synchrotron beam to do diffraction through the battery without opening it, a good Mn3O4 structure is observed. The Clear Science staff will have a paper out about this soon … our preliminary paper on the technique is here.

We aren’t the first people to identify Mn3O4 as the slow-rate product. The Handbook of Batteries gives the same reaction as we have written above. (Wikipedia lists a different reaction, which is not well supported by the literature.)

A battery scientist’s trivial dilemma
You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)
Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:
3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO
The 303/357 is a silver oxide battery having the overall reaction:
Zn + Ag2O = 2 Ag + ZnO
They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

A battery scientist’s trivial dilemma

You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)

Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:

  • 3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO

The 303/357 is a silver oxide battery having the overall reaction:

  • Zn + Ag2O = 2 Ag + ZnO

They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

freshphotons:

"Of the 118 elements that make up everything—from the compounds in a chemists arsenal to consumer products on the shelf—44 will face supply limitations in the coming years. These critical elements include rare earth elements, precious metals, and even life essentials like Phosphorus. Research into more abundant alternatives, more efficient uses, recycling and recovery will help mitigate risks and move industry us towards sustainable supply chains." Via.

A while back Clear Science used the example of tellurium (Te, element 52) to illustrate how obtaining enough of a specific material can be challenging.

freshphotons:

"Of the 118 elements that make up everything—from the compounds in a chemists arsenal to consumer products on the shelf—44 will face supply limitations in the coming years. These critical elements include rare earth elements, precious metals, and even life essentials like Phosphorus. Research into more abundant alternatives, more efficient uses, recycling and recovery will help mitigate risks and move industry us towards sustainable supply chains." Via.

A while back Clear Science used the example of tellurium (Te, element 52) to illustrate how obtaining enough of a specific material can be challenging.

"A crate of oranges hastily filled at the orchard can be more efficiently packed if vigorously shaken a few times to eliminate waste space. In a similar way, atoms loosely collected or disordered in space can become more energetically stable by bonding together into an ordered crystal structure."

Introduction to Crystal Chemistry, by Howard W. Jaffe

Richard Wool from the University of Delaware won the 2013 Presidential Green Chemistry Challenge Award. His research group works to develop replacements for energy and pollution intensive materials. Leather is one example. In this video he talks about ecoleather, which is made from soybean oil and natural fibers derived from chicken feathers and flax.

Goals like this are good for people who like science and want to work with material and chemistry. People have used leather for thousands of years because it has a lot of properties that make it useful and valuable. But it’s also a material with a significant environmental impact (for example the chemicals used for tanning). Coming up with more sustainable replacement materials is not always easy. So maybe some young Clear Scientists should think about how to do more of that.

Oxides form on the surfaces of metals because in the atmosphere they are in contact with oxygen. The nature of these oxides affect how we think of the metals themselves. For example everyone knows that if you leave iron laying around, it will get rusty.
The oxide layer on aluminum is very thin and adheres to the aluminum, insulating it from air and protecting it from oxidizing further. This is why we think of aluminum as a material that doesn’t corrode. (By the way, this aluminum oxide is the same compound that many gems are made of.)

Oxides form on the surfaces of metals because in the atmosphere they are in contact with oxygen. The nature of these oxides affect how we think of the metals themselves. For example everyone knows that if you leave iron laying around, it will get rusty.

The oxide layer on aluminum is very thin and adheres to the aluminum, insulating it from air and protecting it from oxidizing further. This is why we think of aluminum as a material that doesn’t corrode. (By the way, this aluminum oxide is the same compound that many gems are made of.)

Since the oxide of osmium is volatile (i.e. it evaporates) and you can smell it, osmium is seldom used for anything practical as a pure substance. However one characteristic of osmium is that it is a very dense, hard metal. For materials that need to be hard and resistant to wear, like old school pens and phonograph needles, osmium used to be used, alloyed with other metals. Like in the Osmiroid pen tip. (photo credit)

Since the oxide of osmium is volatile (i.e. it evaporates) and you can smell it, osmium is seldom used for anything practical as a pure substance. However one characteristic of osmium is that it is a very dense, hard metal. For materials that need to be hard and resistant to wear, like old school pens and phonograph needles, osmium used to be used, alloyed with other metals. Like in the Osmiroid pen tip. (photo credit)

Here on Earth we live in an atmosphere containing a reactive compound called oxygen. It’s necessary for life as we know it to exist! It also reacts with most materials. For example, metals form oxides on their outside surfaces where they touch oxygen.
The way we think of metals has a lot to do with what this oxide is like. Everyone knows that iron rusts. This is because Fe2O3 is the oxide formed on iron, which is reddish and powdery and sticks to the iron surface. On the other hand, osmium forms osmium tetroxide (“osmium with four oxygens”)  OsO4 which is volatile and evaporates into the air. Since it’s a gas you can smell it, and this is why osmium has a name that basically means “a smell.”

Here on Earth we live in an atmosphere containing a reactive compound called oxygen. It’s necessary for life as we know it to exist! It also reacts with most materials. For example, metals form oxides on their outside surfaces where they touch oxygen.

The way we think of metals has a lot to do with what this oxide is like. Everyone knows that iron rusts. This is because Fe2O3 is the oxide formed on iron, which is reddish and powdery and sticks to the iron surface. On the other hand, osmium forms osmium tetroxide (“osmium with four oxygens”)  OsO4 which is volatile and evaporates into the air. Since it’s a gas you can smell it, and this is why osmium has a name that basically means “a smell.”

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.

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.)