Rigid substances

Solid— is a rigid substance with a definite shape... 

If some monomers do in fact exhibit liquid crystal properties, the polsrmers obtained on their basis are rigid substances featuring high softening points wi-... 

On the other hand, cellulose—also known as fiber—is a stiffer and more rigid substance. Cellulose is the main structural component of plants. The bonding in cellulose makes it indigestible by humans. When we eat cellulose, it passes right through the intestine, providing bulk to stools and preventing constipation. 

Poly(ethylene terephthalate) is a colourless rigid substance. Because of its structural regularity, the polymer readily crystallizes and the physical properties of the bulk material are greatly affected by the extent of crystallinity, which, in turn, is largely determined by the previous history of the material. In the production of fibre, the molten polymer is extruded through spinnerets into air at normal temperature. The filaments are thus rapidly cooled and are largely... 

Polyfethylene terephthalate) is a colourless rigid substance. Because of its structural regularity, the polymer readily crystallizes and the physical pro-... 

Crude oil is recovered from the reservoir mixed with a variety of substances gases, water, and dirt (minerals) (4). Thus, refining actually commences with the production of fluids from the weU or reservoir and is followed by pretreatment operations that are appHed to the cmde oil either at the refinery or prior to transportation. Pipeline operators, for iastance, are iasistent upon the quahty of the fluids put iato the pipelines therefore, any cmde oil to be shipped by pipeline or, for that matter, by any other form of transportation must meet rigid specifications ia regard to water and salt content. In some iastances, sulfur content, nitrogen content, and viscosity may also be specified. 

PRESSURE SYSTEM Defined in the Pressure System Safety Regulations 2000 as a system containing one or more pressure vessels of rigid construction, any associated pipework and protective devices the pipework with its protective devices to which a transportable gas container is, or is intended to be, connected or a pipeline and its protective devices which contains or is liable to contain a relevant fluid, but does not include a transportable gas container. Here relevant fluid is steam any fluid or mixture of fluids which is at a pressure of >0.5 bar above atmospheric pressure, and which fluid or a mixture of fluids is a gas, or a liquid which would have a vapour pressure of >0.5 bar above atmospheric pressure when in equilibrium with its vapour at either tlie actual temperature of the liquid or 17.5°C or a gas dissolved under pressure in a solvent contained in a porous substance at ambient temperamre and which could be released from the solvent with the application of heat. 

Diatomaceous earth A fine, siliceous (made of silica) "earth" composed mainly of the skeletal remains of diatoms (single cell microscopic algae with rigid internal structure consisting mainly of silica). Tests prove that DE leaches unacceptable amounts of silicate into the water for fish health. If used as a filter substance, a silicone removing resin should be employed afterwards. 

This class of material does not set and must be held in position by a rigid cement or some mechanical means. A material commonly used is asbestos fibre mixed with various other substances such as china clay, sand, etc. and plasticised with some form of oil or tar. 

When iodine chloride is heated to 27°C, the weak intermolecular forces are unable to keep the molecules rigidly aligned, and the solid melts. Dipole forces are still important in the liquid state, because the polar molecules remain close to one another. Only in the gas, where the molecules are far apart, do the effects of dipole forces become negligible. Hence boiling points as well as melting points of polar compounds such as Id are somewhat higher than those of nonpolar substances of comparable molar mass. This effect is shown in Table 9.3. 

Given these differences between rigid and flexible conduit, let us examine the differences between steel and RTR pipe, both of which are, of course, flexible conduits. First, steel pipe is by definition constructed from a material, steel, that for our purposes is a homogeneous isotropic substance. Therefore, steel pipe can be considered to have the same material properties in all directions that is, it is equally strong in both the hoop and longitudinal directions [Fig. 4-2(b)]. 

In Chapter 4 we considered gases, in which intermolecular forces play only a minor role. Here, we deal with liquids and solids, in which the forces that hold molecules together are of crucial importance for determining the physical properties of bulk samples. Individual water molecules, for instance, are not wet, but bulk water is wet because water molecules are attracted to other substances and spread over their surfaces. Individual water molecules neither freeze nor boil, but bulk water does, because in the process of freezing molecules stick together and form a rigid array and in boiling they separate from one another and form a gas. 

Self-Test 9.9A The initial partial pressures of nitrogen and hydrogen in a rigid, sealed vessel are 0.010 and 0.020 bar, respectively. The mixture is heated to a temperature at which K = 0.11 for N2(g) + 3 H2(g) 2 NH3(g). What are the equilibrium partial pressures of each substance in the reaction mixture ... 

In diamond, each carbon atom is sp3 hybridized and linked tetrahedrally to its four neighbors, with all electrons in C C cr-bonds (Fig. 14.30). Diamond is a rigid, transparent, electrically insulating solid. It is the hardest substance known and the best conductor ol heat, being about five times better than copper. These last two properties make it an ideal abrasive, because it can scratch all other substances, yet the heat generated by friction is quickly conducted away. 

The interstitial carbides are compounds formed by the direct reaction of a d-block metal and carbon at temperatures above 2000°C. In these compounds, the C atoms occupy the gaps between the metal atoms, as do the H atoms in metallic hydrides (see Fig. 14.9). Here, however, the C atoms pin the metal atoms together into a rigid structure, resulting in very hard substances with melting points often well above 3000°C. Tungsten carbide, WC, is used for the cutting surfaces of drills, and iron carbide, FesC, is an important component of steel. 

In general compounds with heteroatoms (N, O, S and P) are more amenable to fluorescence reactions" than pure hydrocarbons. Under the influence of the catalytic sorbents substances rich in Jt-electrons are formed, that conjugate to rigid reaction products that are fluorescent when appropriately excited. The formation of fluorescent derivatives is frequently encouraged by gassing with nitrogen or carbon dioxide. 

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