Sapphire , synthetic

Aluminium oxide occurs naturally as emery (an impure form) and as corundum. Corundum is a crystalline form which may be coloured by traces of impurity, for example as ruby (red) and sapphire (blue). Small synthetic rubies and sapphires have been made by heating alumina with the colouring oxide in an oxy-hydrogen flame. 

The compounds of greatest importance are aluminum oxide, the sulfate, and the soluble sulfate with potassium (alum). The oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery, and is used in glassmaking and refractories. Synthetic ruby and sapphire are used in lasers for producing coherent light. 

Synthetic gemstone materials often have multiple uses. Synthetic mby and colodess sapphire are used for watch bearings, unscratchable watch crystals, and bar-code reader windows. Synthetic quartz oscillators are used for precision time-keeping, citizen s band radio (CB) crystals, and filters. Synthetic mby, emerald, and garnets are used for masers and lasers (qv). 

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Examples are the beryl, comndum, and quart2 families. Quart2 has poor optical properties (RI = 1.55, DISP = 0.013), but becomes of gemological interest when it exhibits attractive colors. Any material can have its color modified by the addition of various impurities synthetic mby, sapphires, and spinel are produced commercially in over 100 colors (2). Synthetic cubic 2irconia has been made in essentially all colors of the spectmm (11), but only the colorless diamond imitation is produced commercially in any quantity. 

Fig. 1. The Verneuil technique, or flame-fusion growth, as used for synthetic mby and sapphire.

Monochromator 663, 791 Monodentate ligand 51 Morphine (and codeine) D. of (fu) 740 Mortar agate, 155 mullite, 155 percussion, 155 synthetic sapphire, 155 Muffle furnace 97 Multielement analysis 174, 184, 775 Multiple range indicators 268 Murexide 316... 

Sapphyrins were discovered serendipitously by Woodward33 during the course of synthetic studies directed towards the total synthesis of vitamin B, 2. The sapphyrins were the first example of expanded porphyrins in the literature. Due to sapphyrin exhibiting a deep-blue color in the crystalline state and intense green in solution. Woodward coined the expression sapphyrin with reference to the deep-blue color of sapphire stones. 

The critical part of the valve consists of a synthetic sapphire ball resting on a seat. The seat may be of stainless steel, PTFE or, more usually, also of sapphire. When the flow is directed against the ball the ball moves forward allowing the liquid to flow past it. When the direction of pressure changes resulting in potential flow-back through the valve, the ball falls back on its seat and arrests the flow. 

Vemeuil A process for growing single crystals of refractory compounds. The powdered material is dropped through an oxy-hydrogen flame and the product, consisting of microscopic molten droplets, is collected on a seed crystal. As the liquid mass reaches a cooler zone it crystallizes in the form of a single crystal known as a boule. Invented by A. V. L. Vemeuil at the Museum of Natural History, Paris, who made synthetic rabies and sapphires in this way. 

Sapphires are naturally occurring gem stones, and are transparent to translucent. We know from ancient records that they have always been highly prized. Natural sapphires are found in many igneous rocks, especially syenites and pegmatites. Alternatively, synthetic sapphires may be made by doping aluminium oxide AI2O3 with a chro-mophore. 

First, the zero line is recorded using two empty crucibles. Next, a calibrant substance (usually alumina, i.e., synthetic sapphire) is placed in the sample crucible and the temperature program is repeated. Finally, the calibrant is replaced by the sample under study (keeping the crucible) and the temperature program run a third time. Based on equations 12.20 and 12.21, it can be concluded that the ordinate difference between the traces of the calibrant curve and of the zero line obtained for a given time t leads to the corresponding value of fcp ... 

Aluminum oxide is used to make synthetic rubies and sapphires for lasers beams. It has many pharmaceutical uses, including ointments, toothpaste, deodorants, and shaving creams. 

A different system has been introduced by Index Instruments [2]. This modular analysis system (MAS) provides the analysis of up to four different parameters refractive index, density, colour and optical rotation. A wide range of viscosities can be handled. The analysis, wash and drying times can be selected by computer control so that crosscontamination can be reduced to undetectable levels. Samples are only in contact with inert materials such as glass, synthetic sapphire, PTFE and 316 stainless steel. 

The middle knife edge rests on a plate on the central column of the balance and is the point of support. In an analytical balance, the knife edges and plate are made from agate or synthetic sapphire. The stirrups carrying the balance pans rest on the side knife edges. The beam is provided with a long pointer that indicates the deviation of the beam from a horizontal position on a scale. When the beam is horizontal, the pointer is opposite zero of the scale. 

Spinel. Colorless (pure), blue (Co), and olher colored synthelic spinels made by the Vemeuil process are widely seen in class rings and in other jewelry uses, where the blue is often mislabeled as synthetic sapphire. 

Spinel is a colorless magnesium aluminate (MgAl204) of cubic structure. It is hard and durable, but, like white sapphire, it is not a good diamond substitute because it has a low refractive index and lacks brilliance. However, it is readily doped to produce other gems of various colors. Artificial ruby, for example, is often natural red spinel, and most synthetic blue sapphires on the market are actually blue spinel. 

Figure 4.16 Polarized absorption spectra of natural and synthetic sapphires (from Bums and Bums, 1984a). (a) Natural yellow sapphire (b) natural dark blue sapphire (c) synthetic Ti-doped A1203 (d) synthetic Fe-Ti-doped A1203. —Ellc spectra -----EJx...

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