This Day in Science History - February 16 - Julius Thomsen
His hypothesis would be later be shown to be correct. In 1895, Carl von Linde would discover these elements and call them the noble gases. Find out more about Thomsen and what else occurred on this day in science history.
Follow About.com Chemistry on Facebook or Twitter.
Wordless Wednesday - Rainbow in a Glass
How Haircoloring Works
In the Beginning
The first safe commercial haircolor was created in 1909 by French chemist Eugene Schuller, using the chemical paraphenylenediamine. How does haircolor work? It's the result of a series of chemical reactions between the molecules in hair, pigments, as well as peroxide and ammonia, if present.What is Hair?
Hair is mainly keratin, the same protein found in skin and fingernails. The natural color of hair depends on the ratio and quantities of two other proteins, eumelanin and phaeomelanin. Eumelanin is responsible for brown to black hair shades while phaeomelanin is responsible for golden blond, ginger, and red colors. The absence of either type of melanin produces white/gray hair.
Natural Colorants
People have been coloring their hair for thousands of years using plants and minerals. Some of these natural agents contain pigments (e.g., henna, black walnut shells) and others contain natural bleaching agents or cause reactions that change the color of hair (e.g., vinegar). Natural pigments generally work by coating the hair shaft with color. Some natural colorants last through several shampoos, but they aren't necessarily safer or more gentle than modern formulations. It's difficult to get consistent results using natural colorants, plus some people are allergic to the ingredients.
Temporary Hair Color
Temporary or semi-permanent haircolors may deposit acidic dyes onto the outside of the hair shaft or may consist of small pigment molecules that can slip inside the hair shaft, using a small amount of peroxide or none at all. In some cases, a collection of several colorant molecules enter the hair to form a larger complex inside the hair shaft. Shampooing will eventually dislodge temporary hair color. These products don't contain ammonia, meaning the hair shaft isn't opened up during processing and the hair's natural color is retained once the product washes out.
How Lightening Works
Bleach is used to lighten hair. The bleach reacts with the melanin in hair, removing the color in an irreversible chemical reaction. The bleach oxidizes the melanin molecule. The melanin is still present, but the oxidized molecule is colorless. However, bleached hair tends to have a pale yellow tint. The yellow color is the natural color of keratin, the structural protein in hair. Also, bleach reacts more readily with the dark eumelanin pigment than with the phaeomelanin, so some gold or red residual color may remain after lightening. Hydrogen peroxide is one of the most common lightening agents. The peroxide is used in an alkaline solution, which opens the hair shaft to allow the peroxide to react with the melanin.
Permanent Hair Color
The outer layer of the hair shaft, its cuticle, must be opened before permanent color can be deposited into the hair. Once the cuticle is open, the dye reacts with the inner portion of the hair, the cortex, to deposit or remove the color. Most permanent hair colors use a two-step process (usually occurring simultaneously) which first removes the original color of the hair and then deposits a new color. It's essentially the same process as lightening, except a colorant is then bonded within the hair shaft. Ammonia is the alkaline chemical that opens the cuticle and allows the hair color to penetrate the cortex of the hair. It also acts as a catalyst when the permanent hair color comes together with the peroxide. Peroxide is used as the developer or oxidizing agent. The developer removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odor of haircolor. As the melanin is decolorized, a new permanent color is bonded to the hair cortex. Various types of alcohols and conditioners may also be present in hair color. The conditioners close the cuticle after coloring to seal in and protect the new color.
Why Hair Turns Green from a Pool &124; Can Hair Turn White Overnight?
This Day in Science History - February 15 - Galileo Galilei
Before Galileo, science was not considered a profession. Typically, people who did 'science' were considered natural philosophers and held positions as medical doctors, mathematicians or priests with extra time on their hands. The name philosopher was typically used because it was just as likely for someone to explain a phenomenon by what they believed happened through other philosophies or their own ideas as easily as their own observations.
Galileo was one of the first to break away from Aristotle's four terrestrial elements of earth, air, fire and water with a new basic element of corporeal matter. He was the first to express the belief that the basic laws of science could be broken down into mathematics. He was among the first to take a closer look at the skies above with a telescope.
His life is generally used as the beginning point of the history of modern science. His philosophy of observe first, explain second and observe some more would become the foundation of the modern scientific method. Find out what else occurred on this day in science history.
Can You Pass a 3rd Grade Science Test?
Keep Valentine's Day Flowers Fresh
Presenting a bunch of wilted flowers on Valentine's Day may not convey the right message, unless that message runs along the lines of 'My love for you has faded, like these pathetic flowers' or 'See, I got you something for Valentine's Day, but I'm not out to impress you." I'd suggest cutting the heads off of the flowers or maybe giving black flowers if the former sentiment applies. If your heart is in the right place, however, either keep your flowers healthy or consider giving a different gift.
If you get Valentine's Day flowers from a florist, they probably include a packet of floral preservative, but if you pick flowers yourself or decide to custom-color them, you may want to make up some floral preservative to help keep your flowers fresh and beautiful. Though you can pay a lot for pre-packaged flower preservative, it's really easy and economical to make it yourself. Your preservative needs to contain water, food for the flowers, and a disinfectant to prevent bacteria, mold, and fungi from growing. Possibly the easiest way to make flower food is to mix together a can of Sprite™ (or other non-cola carbonated soft drink), refill the can with water, and add a splash of household bleach. If you don't have those ingredients handy, I have additional recipes for floral preservatives that you can try. Trim the stems of your flowers at an angle and underwater (so tiny air bubbles don't stick on the stems and prevent water from moving in). Flowers with long stems, like tulips, will benefit from having support for the first couple of hours after you put them in water. Either leave the flowers in their wrapping for loosely tie them together. You can remove the support once the stems are hydrated and strong. Keep your flowers in a cool location, preferably out of direct sunlight. Most flowers will last about a week if they are given proper care.
This Day in Science History - February 14 - Julius Nieuwland
Nieuwland discovered he could polymerize acetylene into a rubber-like jelly of divinyl acetylene. The story might have ended there except Elmer Bolton of DuPont attended a lecture of Nieuwland's. Many industries were looking for an alternative source of rubber. Rubber is a natural product produced from latex of the para rubber tree. The majority of the world's rubber came from plantations in the Amazonian rainforest. Chemical engineers around the world were trying to discover a useful synthetic alternative. Bolton acquired the rights to further develop Nieuwland's discovery for DuPont. Scientists at DuPont collaborated with Nieuwland to produce neoprene.
Nieuland is also known for his discovery of the chemical weapon lewisite. He discovered the reaction during his acetylene research, but abandoned further research because of it's poisonous nature. When his research was weaponized to produce lewisite, he nearly gave up chemical research entirely. Find out what else occurred on this day in science history.
Follow About.com Chemistry on Facebook or Twitter.
This Day in Science History - February 13 - Étienne Geoffroy
Anyone who has ever mixed two items together knows some things combine better than others. In chemistry, two different chemical species' affinity is a property that shows how likely a chemical reaction will occur when mixed. Reagents with strong affinity are more likely to react with each other than reagents with little affinity to each other. Geoffroy's table had a series of reagents across the top with other reagents with high affinity with these elements listed below. This table became a standard table for 18th Century chemists until the end of the century when it was shown the amount of a reagent drove the reaction.
Find out what else occurred on this day in science history.
How To Cook a Frozen Pizza on the Stove - Science Experiment
So, the other day I found myself in a hotel room with a frozen pizza and a stove, but no oven. I did what any hungry scientist would do. I set out to determine whether or not it was possible to cook a frozen pizza on the stove. In order for the experiment to be a success, the pizza had to be good enough to eat. Well, also I would have considered the experiment a failure if there had been a fire. That is not generally a condition of failure in my projects, but when I'm on the road I'm a little less of a pyro.Anyway, I wrote up the project in terms of the scientific method because I think this is the sort of everyday science that people can relate to more easily than an experiment using hard-to-pronounce chemicals... Let's cook pizza!
Bounce a Rubber Egg
My daughter's favorite science project is making rubber eggs. You only need two ingredients for the rubber egg project, an egg and some vinegar. You'll get somewhat different results depending on whether you start with a raw egg or a hard-boiled egg, so try both! The project is safe enough for young kids and doesn't make a mess (unless you throw the egg hard), plus the resulting egg can be used as a bouncy ball. Try it out...