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This is one of the most beautiful and largest crystals you can grow overnight. All you need is hot water and potassium alum, also known as potash alum. Potassium alum may be sold as a 'deodorant crystal' or in solution for use as an astringent. I got the powder for growing this crystal from a Smithsonian crystal-growing kit (labeled as potassium alum). Prepare the Solution All you need to do to prepare the crystal solution is to mix as much potassium alum as will dissolve into 1 cup of very hot water. You can add food coloring to tint the crystals. The natural color of the crystals would be clear or white. Grow Crystals I poured the solution into a clean bowl, trying to avoid getting any undissolved material into the new container. Allow the crystals to grow overnight. If your solution is very darkly colored, you won't be able to see whether or not you have crystal growth. You can use a spoon or fork to scrape crystals from the bottom. To get a large single crystal like t...

There aren't any 'air' molecules, but you already knew this, right? Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Several other additional elements and compounds are present. Although this CRC table does not list water vapor, air can contain as much as 5% water vapor, more commonly ranging from 1-3%. The 1-5% range places water vapor as the third most common gas (which alters the other percentages accordingly). This is composition of air in percent by volume, at sea level at 15°C and 101325 Pa. Nitrogen -- N 2 -- 78.084% Oxygen -- O 2 -- 20.9476% Argon -- Ar -- 0.934% Carbon Dioxide -- CO 2 -- 0.0314% Neon -- Ne -- 0.001818% Methane -- CH 4 -- 0.0002% Helium -- He -- 0.000524% Krypton -- Kr -- 0.000114% Hydrogen -- H 2 -- 0.00005% Xenon -- Xe -- 0.0000087% Ozone -- O 3 -- 0.000007% Nitrogen Dioxide -- NO 2 -- 0.000002% Iodine -- I 2 -- 0.000001% Carbon Monoxide -- CO --...

In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans , who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives which were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement. Cements used in construction are characterized as hydraulic or non-hydraulic . The most important use of cement is the production of mortar and concrete —the bonding of natural or artificial aggregates to form a strong building material which is durable in the face of normal environmental effects. Concrete should not be confused with cement because the term cement refers only to the dry powder substance used to bind the aggregate materials of concrete. Upon t...

If you've ever poured hydrogen peroxide solution onto a cut and didn't experience the expected fizz, it's likely your bottle of hydrogen peroxide has become a bottle of plain water. The 3% hydrogen peroxide solution you can buy for use as a disinfectant typically has a shelf life of at least a year if the bottle is unopened, but only lasts 30-45 days once the seal has been broken. As soon as you expose the peroxide solution to air, it starts to react to form water. Also, if you contaminate the bottle (e.g., by dipping a swab or finger into the bottle), you can expect the effectiveness of the remaining liquid to be compromised.So, if you have a bottle of hydrogen peroxide that has been sitting in your medicine cabinet for a few years, it would be a good idea to replace it. If you've opened the bottle at any point, its activity is long-gone. If you feel like testing the solution. Solvay Chemicals describes a test you can perform to assess the remaining activi