Carved oxidation

It darkens with exposure to the ultraviolet rays in sunlight, and the surface becomes opaque due to oxidation. Examples of beads carved in the Stone Age are usually a deep, dull, reddish colour, but when viewed by transmitted light they glow a deep brownish-red. If one of these beads were broken the inside would be much paler and probably clear. The length of time taken for this to happen varies according to where and how the amber has been stored. It can take from several years to several hundred years to occur naturally, but the effect can be simulated through treatment. 

As a member of the corundum family of minerals, sapphire (the September birthstone) consists primarily of aluminum oxide, AI2O3. Small amounts of iron and titanium give it its rich dark blue color. Gem cutter Norman Maness carved a giant sapphire into the likeness of Abraham Lincoln. If this 2302-carat sapphire were pure aluminum oxide, how many moles of AI2O3 would it contain (There are exactly 5 carats per gram.)... 

Calcium is found in rocks as the carbonate, fluoride, oxide, phosphate, and sulfate. In purified forms, each of these minerals has practical applications. Limestone, calcite, and marble occur in the form of calcium carbonate (CaC03) and are used as building materials. In addition, marble is carved to make statues. Portland cement—derived mainly from calcium carbonate and calcium silicates—is a staple of the building industry. Calcium carbonate is taken to relieve heartburn antacids like... 

All of the aforementioned tetracyanoplatinate complexes. Table IV, form columnar structures in the solid. The partially oxidized complexes exhibit short uniform metal-metal spacings and the physical properties characteristic of metallic systems. The K2Pt(CN)4Xo.3(HaO)a complexes, due to the ease of growing large defect-free crystals, have been the most extensively studied inorganic one-dimensional systems. In addition, the ability to carve these crystals with a sharp knife (364a) is an aid in performing some physical measurements. 

These characteristics of polysiloxanes are also reflected in their many other properties such as their high water repellency (hydrophobicity), low surface tension etc. Among the other desirable properties of polysiloxanes are their high gas permeability, thermal stability, oxidative stability and low volatility. In addition, their fire points are quite high and so they do not present a fire hazard [1, 5, 7]. Also, polysiloxanes have high biocompatibility and very low toxicity. These properties of polysiloxanes have helped them to carve out a niche for themselves in the area of polymers and have helped their ever expanding utility some of which are outlined in the following section. 

These types of boxes are well known for their thick layers of lacquers which are then carved. Two types of colors have been used to pigment oriental lacquer boxes even in early periods. One Is the vermilion color caused by an iron oxide pigment and the black color which Is caused by either magnetite, elemental iron or carbon black. Heavy pigmentation is needed because processed raw urushi used for painting has a deep bluelsh/black to black color. 

An interesting class of nonionic surfactants that has developed as a result of advances in block polymerization techniques is that of the polyalkylene oxide copolymers. Such materials exhibit many interesting and useful properties that have allowed them to carve out a special niche in the surfactant formulation world. Although they are relatively low-molecular-weight materials as polymers go, they are much larger than normal surfactant molecules and for that reason will be discussed in more detail in Chapter 7. 

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