Me too, but seeing as I'm a chemist, I figure why not investigate, and learn about some molecules. Plus, wouldn't it be impressive if someone looks at the back of something, and says, man I wonder what so and so does, and you quickly retort a scientific sounding response.
I took a bottle of Irish Spring Body Wash, and analyzed each of on the ingredients listed on the bottle. The order indicates the relative amounts, so there is more of the first listed component than the second, and so on. Enjoy!
Water
Water covers 71% of the surface of the earth. You're probably pretty familiar with it. Odds are you drink in it, and bath in it. What is it doing in my soap? Well, if you just had all of these chemicals concentrated, it would be pretty strong, and not very good for you. However diluted, these chemicals can do their wonders, which are described below.
Sodium Laureth Sulfate
Sodium laureth sulfate is a synthetic detergent. It is abbreviated as SLES. Its effect is to act as a foaming agent, and is an efficient cleaner. The alkyl end of the molecule (the zigzagging end on the right) is fat/oil soluble (soluble meaning that it can be dissolved in a certain substance), so it is able to bind to oils in our skin. The sulfate end on the right is composed of sulfur and oxygen, and is water soluble. Because the molecule has two ends soluble in different materials, it can act as an anchor to pull excess oil from our skin, and can still be washed away. The section of the molecule surrounded by paranthesis and marked with an n indicates that that section of the molecule will repeat n time, where n is a whole number. Often times with SLES, n is 2 or 3.
This compound can be classified as a detergent, and a surfactant. A surfactant is a molecule that reduces the surface tension of what it is emerged in.
There are rumors that this compound is carcinogenic (causes cancer), however these are just rumors; it is not true. It's biggest danger is being irritating to those with sensitive skin. It is very common in soaps and toothpastes, etc. For more on this being disproven as being carcinogenic, see below in the references.
Cocamidopropyl Betaine
Cocamidopropyl Betaine has similar properties to that of SLES. It is abbreviated as CAPB. You can see that it has a similar structure. The alkyl chain on the left is again fat/oil soluble, and the carboxylate (the carbon and two oxygens) group on the right is water soluble, and has the same effect as the sulfate in SLES.
The difference between these two molecules is that CAPB is a milder detergent, and it is a more viscous (thicker) compound. Why is it more viscous? Well, it's complicated, if you're feeling brave, feel free to delve into some fluid dynamics, it's not my sort of thing though. The short, simplified version is that bulkier molecules which have strong intermolecular forces (forces that pull the molecules together) are more likely to be a solid, or a viscous liquid. The nitrogen to the right of the oxygen in the line structure is a hydrogen bond donor, and the two double bonded oxygens act as hydrogen bond acceptors. Hydrogen bonding, is what makes water such an interesting molecule.
CAPB essentially dilutes SLES, and makes it less irritating, but not so much as to render it ineffective.
Sodium Chloride
Sodium chloride has a much more common name; salt. You encounter salt every day, and is the reason that salty foods are high in sodium; because salt is made of sodium. However what is it doing in my cleaning agent? Well, it has two major functions.
It "softens" water. You've probably heard of hard water. Hard water is laced with magnesium and calcium ions, which leave a residue, or scum in your bathtub, etc. The way sodium chloride softens water, is by "exchanging ions" with the magnesium and calcium ions. This reduces the negative effects of the magnesium and calcium ions, and helps prevent the residue from being left on you or your bathtub.
Salt is also an antiseptic, which helps prevent and clean bacteria from your skin.
Decyl Glucoside
This is another detergent/surfactant. It is one of the milder agents listed here, and also acts as one of the best foaming agents. As you can tell from the lack of (+)'s and (-)'s shown in its structure, it is non-ionic surfactant, which generally means it is more environmentally friendly, and it is also much less likely to be left as a residue.
Fragrance
Well, this is a vague term. Fragrance chemistry is a pretty specialized fields, and is pretty self-explanatory. It consists of engineering different compounds or mixtures of to produce a certain scent. So, "fragrance" could be a whole slew of things. I'm not going to go into it because it's useless since they don't tell us which fragrances they're using. If you're interested, google something along the lines of "fragrance used in soaps".
DMDM Hydantoin
Now this is interesting. This molecule is a preservative, which releases formaldehyde. Yeah, formaldehyde. Your first thought was probably of dead bodies, but formaldehyde is actually used in more things than you probably know about. For instance, it is even used in vaccinations, and to treat warts. All new to me. It is used in our product because formaldehyde is used to kill bacteria and fungi, and acts as preservative. These are also two reasons it's used to preserve dead bodies actually.
Formaldehyde is toxic to the body, becuase it is converted into formic acid. This has the effect of lowering the pH of our blood (making it more acidic), which is very bad. However, luckily our body is buffered, which means it resists changes in pH. I won't go into great detail here, but I will list just a few ways the body does this. our blood has carbon dioxide in it, which produces carbonic acid to neutralize any excess base we might have in us. Bicarbonate is in our blood as well which acts as a base to get rid of any acid in our blood. One of the main functions of the kidney is to excrete acid; our urine is much more acidic than our blood. In case you were wondering, our blood has a pH of about 7.4, which is just slightly more basic than water, which is often used as a standard, and has a pH of 7.
That was quite a tangent, but hopefully an interesting one.
Polyquaternium-7
Another interesting molecule. Polyquaternium-7 actually coats hairs on the body with a very thin film. The purpose is to make the hair less electrostatic and easier to comb, which will make it feel smoother. This is true for both the hair on your head, and body hair. If you're interested in seeing some cool microscopic pictures of hair before and after being coated with Polyquaternium-7, click on the "Morphological analysis of polymers on hair fibers by SEM and AFM" link in the references below.
Tetrasodium EDTA
Another component whose purpose is to soften water. Tetrasodium EDTA has four (which is why it's TETRA) sodium ions, which can be exchanged with magnesium and calcium ions from hard water. EDTA is very common in laboratory use for general ion exchange purposes.
Citric Acid
Get ready for it, Citric acid is used to... soften water! A recurring theme, but it is important. However, that is not the only purpose of citric acid. You're most used to hearing about citric acid from being in fruits. It makes foods taste sour (acidic). In terms of our product, citric acid also opens up the outer layer of hair, the cuticle, and allow the other detergents and such to have a deeper cleaning effects.
FD&C Green No. 3
FD&C stands for the US Food, Drug and Cosmetic Act. There are currently seven artificial food colorings permitted in the US. Natural food colorings such as caramel coloring, often found in cola are in a separate category. The name of FD&C Green No. 3 is Fast Green FCF. The reason food colorings are different colors (as well as why anything a different color) is due to the wavelength that light is absorbed at in a molecule. This varies based on structure and composition of a molecule. This coloring is used to give the product it's green color.
FD&C Yellow No. 5
See the above item for a brief explanation on food coloring and their name. The name of the FD&C Yellow No. 5 compound is Tartrazine. Its structure is shown below. This is the dye found in Mountain Dew and simliar sodas. There is an urban legend that ingesting this dye will shrink your testicles and/or penis. This is nonsense. Anyhow, this coloring helps reduce the intensity of the green in the product.
I hope you enjoyed this journey of chemistry, please leave any feedback in the commments below. If you enjoyed this and want more, just suggest a product.
References:
Wikipedia - Sodium Laureth Sulfate
Rumor: Sodium Lauryl Sulfate Causes Cancer
Wikipedia - Cocamidopropyl Betaine
Ingredients - Cocamidopropyl Betaine
Wikipedia - Viscosity
The Many Uses of Salt
Other Uses for Salt
Wikipedia - Decyl Glucoside
The Difference between anionic and nonionic surfactant, and its application to detergent
Ingredients - DMDM Hydantoin
Wikipedia - Formaldehyde
Morphological analysis of polymers on hair fibers by SEM and AFM
Wikipedia - Tetrasodium EDTA
Wikipedia - Citric Acid
Wikipedia - Fast Green FCF
Wikipedia - Tartrazine
Urban Legends Reference Pages: Mountain Dew Shrinks Testicles
Wikipedia - Water
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