Fusion point

Reoxidation occurs when the metallic iron in hot DRI reacts with oxygen in the air to form either Ee O or Ee202. The reaction continues as long as the DRI remains hot and sufficient oxygen is avadable. Because reoxidation reactions are exothermic and DRI is a good insulator, it is possible that once reoxidation begins inside a pde, the DRI temperature increases and accelerates the reoxidation rate. Although the inner core of the pde may reach temperatures up to the fusion point of iron, the maximum temperature of the outer parts of the pde will be much lower because of heat dissipation. 

MetaHic potassium and potassium—sodium alloys are made by the reaction of sodium with fused KCl (8,98) or KOH (8,15). Calcium metal and calcium hydride are prepared by the reduction of granular calcium chloride with sodium or sodium and hydrogen, respectively, at temperatures below the fusion point of the resulting salt mixtures (120,121). 

The simplest analytical procedure is to oxidize a sample in air below the fusion point of the ash. The loss on ignition is reported as graphitic carbon. Refinements are deterrninations of the presence of amorphous carbon by gravity separation with ethylene bromide, or preferably by x-ray diffraction, and carbonates by loss of weight on treating with nitric acid. Corrections for amorphous carbon and carbonates are appHed to the ignition data, but loss of volatile materials and oxidation may introduce errors. 

Refra.ctories, Refractory products are prepared from a wide variety of naturally occurring materials such as chromite [1308-31 -2] and magnesite [546-93-0] or from clays predominandy composed of kaolinite. Increasingly, higher purity synthetic materials are being used to obtain special properties. On the other hand, for many refractory uses, a somewhat lower fusion point than that provided by kaolinite may be adequate, so that clay materials having a moderate amount of other components as, for example, iUite, may be satisfactory. High alumina clays are also used extensively for the manufacture of special types of refractories. 

The bulk density of powdered diatomite varies from 112 to 320 kg/m. The tme specific gravity of diatomite is 2.1 to 2.2, the same as for opaline sihca, or opal (1). The thermal conductivity of bulk quantities of diatomite is low but increases with higher percentages of impurities and a higher density. The fusion point depends on the purity but averages about 1430°C for pure material, which is slightly less than for pure siUca. The addition of chemical agents, such as soda ash, reduces the fusion point. 

Insulation. Diatomite makes an efficient thermal insulator because of its high resistance to heat (fusion point at 1430°C) and its high porosity... 

Scheme 3 illustrates two general annulation procedures, one with the a-halogenoketone moiety incorporated in a cyclic system leading to C—C fused systems. The other, with the heteroatoms already incorporated in a heterocycle, results in a product with a heteroatom at a fusion point. 

In contrast to the above, the reaction of a heterocyclic thione with an a-halogenoketone (Scheme 3) has been widely exploited as a route to [5,6] ring-fused systems with a heteroatom at a ring fusion point. 

The syntheses of ring-fused systems with both C—C and C—-N fusion points are particularly suited for cyclocondensations of this type. Treatment of the 4,5-diaminopyrazole... 

Type of brick Typical composition Approx. bulk density, Ib/fF Fusion point, F. Cbemical nature Deformation under hot loading Apparent porosity, % Perme- abibty Hot strength Thermal shock resistance Cbemical resistance ... 

Phenylacetylene (2, 67). It is stated in the directions that the distilling flask is heated until a temperature of 200° is reached and at that temperature the potassium hydroxide which is used is molten. The potassium hydroxide usually available contains sufficient moisture so that it will liquefy at 200 If pure dry potassium hydroxide is used, it is necessary to add a little water so that the fusion point will be lowered to the point indicated... 

Slag modifiers raise the fusion point or sintering temperature of the ash and directly neutralize any S03 formed. They are based on alkaline-earth metals such as magnesium, calcium, and strontium, or rare-earth metals such as cerium they are available as oxides, salts, or soaps. 

This is the earliest and the most commonly used casting process. It has the advantages of wide metal suitability, low cost, and simple operation. It uses sand as a refractory material. Many types of sand are utilized by the foundry industry. However, because of its wide availability and relatively low cost, silica sand is the one that makes most metal castings. Silica sand is composed of the mineral quartz (Si02), which has a fusion point of approximately 1670°C (3090°F), which is often lowered by the presence of appreciable quantities of minerals with lower fusion points. 

Refractory days (fusion point above 1600 °C but not necessarily white-burning)... 

Crucible material Usable in Usable in air to vacuum to °C °C Fusion point [°C Density [g cm s I Gas tight- ness Resistance against temperature changes Chemical properties... 

Staphylococcal protein A (SPA), with its immunoglobulin binding ability, has been used as an affinity tail for the purification of a human insulin growth factor-1 (lGF-1) fusion. The insertion of an acid-labile Asp-Pro cleavage site at the fusion point allowed the separation of the protein A moiety from lGF-1 (Nilsson et al., 1985). 

Let us first consider the liquid-solid phase transformation. At the melting point (or more appropriately, fusion point for a solidification process), liquid and solid are in equilibrium with each other. At equilibrium, we know that the free energy change for the liquid-solid transition must be zero. We can modify Eq. (2.11) for this situation... 

Procedure Fill a %x4 incb test tube to a depth of 1 inch with the specimen ground to pass a No 16 mesh screen. Submerge the tube to a depth of 2 inches in an oil bath previously heated to 120°, place a thermometer in the EtCell and increase the bath temp at the rate of 2°C per min, while stirring the specimen by means of thermometer. At a temp approx 25° below fusion point the particles soften and tend to cohere, making it difficult to stir. Continue beating and working the mass until it fuses and becomes plastic. Read the "thermoplastic point" as the temp at which the plastic mass can be repeatedly drawn into thread by pulling the thermometer from the mass. Duplicate detns should check within 3°C... 

Sulphur and selenium unite when warmed with the metal 51 when sulphur is triturated with sodium, the reaction proceeds with explosive violence which can be moderated by dilution with common salt. Under boiling toluene, sulphur forms the trisulphide Na2S3. Selenium forms the monoselenide, Na2Se, when heated with sodium. Sodium is attacked by hydrogen sulphide at ordinary temp., and at the fusion point the metal bums in the gas. Gaseous ammonia reacts readily with sodium, and liquid ammonia forms blue soln.—the so-called alkali-ammoniums. 

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