Solid forms

This chapter is concerned with the arrangement of molecules in solids. Crystalline solids 

simple substances separate from solution on cooling as crystals. These crystals have a sharp melting point, which marks precisely the boundary between the liquid and solid states. They also have a definite and consistent shape. This shape is due to the pattern in which the atoms, ions or molecules are arranged. Thus crystals of common salt are always cubic. The arrangement of the Na+ and Cl ions is in a cubic pattern (Fig. 8), which extends in all directions to fill and form the shape of a single crystal. 

Other inorganic compounds have a variety of crystal shapes, in all of which the ions, atoms or molecules are arranged in a definite pattern, held together by ionic or covalent bonds, or by intermolecular attractions, which arise from the polarity (or electrical asymmetry) of the molecules. In diamond, for example, each carbon atom is covalently bonded to four neighbours (Fig. 9) so that the crystal is one giant molecule . This in part accounts for its great strength and hardness. 

In many solids, the molecules are not arranged in any pattern at all. Instead they contain the random arrangement of molecules typical of a liquid, which appears to have become fixed as a solid by cooling. Since there is no pattern of molecules, there is no typical shape to the solid, which is known as an amorphous (shapeless) solid. 

The act of crystallization is a sudden process, which occurs at the precise temperature at which the energy of movement yields to the forces of attraction. In an amorphous solid, the molecules gradually become slower and more closely attracted to one another, until they are so closely packed that they completely impede one another and the substance will not flow. It is impossible to say exactly when this occurs, or even whether the substance has changed from flowing very slowly indeed, to not flowing at all. There is no melting point and the boundary between the solid and the liquid state is blurred. 

Spray drying has been utilized for decades and is still one of the common production methods for enzyme products. Other modes of drying such as freeze drying are typically costly and are not economically justified for the production of large volume, low cost enzyme product. 

FIGURE 6.7 Enzyme granules with matrix (a) and core/shell (b and c) morphologies. 

FIGURE 6.8 Manufacture of enzyme granules (microparticles) by spray drying process. 

The spray dried powders can also be incorporated into more structured particles such as extrudates or high shear granules. These particles can offer other advantages including improved stability and particle integrity. They also have the possibility of including other functional ingredients and customized enzyme release mechanisms. 

Various binders and stabilizers can be used in high shear granulation to produce non-friable particles with different morphologies, which protect enzymes during storage but allow for their ready release in solution during application. 

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Copper(l) oxide, CujO. Red solid formed from Cu(II) salt and hydrazine or heat on CuO. Gives a cheap red glass and a cuprate, KCuO (K2O plus CU2O). 

Copper(II) oxide, CuO. Black solid formed by heating Cu(OH)2, Cu(N03)2, etc. Dissolves in acid to Cu(II) salts, decomposes to CU2O at 800 C. Forms cuprates in solid state reactions. A cuprate(III), KCUO2, is also known. 

Krilium The trade name of a soil conditioner. The solid form of Krilium has as active in-gredienl a copolymer of about equal molar proportions of vinyl ethanoate and the partial methyl ester of maleic acid. It may be formulated with lime, bentonite, etc. In aqueous form, Krilium contains a copolymer of about equal molar proportions of isobutene and ammonium maleamate. Other polymers are also used. 

S02NH) . Colourless crystalline solids formed by the action of ammonia on a solution of sulphuryl chloride in benzene free sulphimide exists only in the polymerized form. 

Tin iy) fluoride, Snp4, stannic fluoride. Polymeric solid formed Sn plus F2 or SnCU plus HF. Very hygroscopic, forms fluoro-stannales(IV) containing [SnFgp ions. 

Vanadium ni) chloride, VCI3. Violet solid formed V plus HCl gas. VCIj bHiO formed from solution. Forms many complexes. 

Vanadium II) chloride, VCI2. Green solid formed VCI4. plus H2. 

Vanadium difluoride, VF2. Blue solid formed H2 plus HF on VF3 or HF on VCI2 at bOO C. 

The sulfur vapor is condensed and recovered in the liquid or solid form. 

Under certain conditions of temperature and pressure, and in the presence of free water, hydrocarbon gases can form hydrates, which are a solid formed by the combination of water molecules and the methane, ethane, propane or butane. Hydrates look like compacted snow, and can form blockages in pipelines and other vessels. Process engineers use correlation techniques and process simulation to predict the possibility of hydrate formation, and prevent its formation by either drying the gas or adding a chemical (such as tri-ethylene glycol), or a combination of both. This is further discussed in SectionlO.1. 

It is clear that if the vapour at a pressure below the triple point is reduced sufficiently in temperature, it will condense directly to the solid form, or, sublimation will ensue. In order that a solid may pass directly... 

The gas is colorless, odorless, and tasteless. The liquid and solid forms are a pale blue color and are strongly paramagnetic. 

What if the analyte is an aqueous ion, such as Pb + In this case we cannot isolate the analyte by filtration because the Pb + is dissolved in the solution s matrix. We can still measure the analyte s mass, however, by chemically converting it to a solid form. If we suspend a pair of Pt electrodes in our solution and apply a sufficiently positive potential between them for a long enough time, we can force the reaction... 

Inclusions, occlusions, and surface adsorbates are called coprecipitates because they represent soluble species that are brought into solid form along with the desired precipitate. Another source of impurities occurs when other species in solution precipitate under the conditions of the analysis. Solution conditions necessary to minimize the solubility of a desired precipitate may lead to the formation of an additional precipitate that interferes in the analysis. For example, the precipitation of nickel dimethylgloxime requires a plT that is slightly basic. Under these conditions, however, any Fe + that might be present precipitates as Fe(01T)3. Finally, since most precipitants are not selective toward a single analyte, there is always a risk that the precipitant will react, sequentially, with more than one species. 

A large family of compounds is based on combination of TTF-type donors and TCNQ-type acceptors. The resulting solids form... 

Properties. Lithium fluoride [7789-24-4] LiF, is a white nonhygroscopic crystaUine material that does not form a hydrate. The properties of lithium fluoride are similar to the aLkaline-earth fluorides. The solubility in water is quite low and chemical reactivity is low, similar to that of calcium fluoride and magnesium fluoride. Several chemical and physical properties of lithium fluoride are listed in Table 1. At high temperatures, lithium fluoride hydroly2es to hydrogen fluoride when heated in the presence of moisture. A bifluoride [12159-92-17, LiF HF, which forms on reaction of LiF with hydrofluoric acid, is unstable to loss of HF in the solid form. 

Surface Protection. The surface properties of fluorosihcones have been studied over a number of years. The CF group has the lowest known intermolecular force of polymer substituents. A study (6) of liquid and solid forms of fluorosihcones has included a comparison to fluorocarbon polymers. The low surface tensions for poly(3,3,3-trifluoropropyl)methylsiloxane and poly(3,3,4,4,5,5,6,6,6-nonafluorohexyl)methylsiloxane both resemble some of the lowest tensions for fluorocarbon polymers, eg, polytetrafluoroethylene. 

Pitch. Pitch used to be stored in solid form at the tar distillery in open bays, from which it was removed by small explosive charges. Loading of the lump pitch by mechanical shovel created a dust ha2ard both at the tar installation and at the customer s, where the lumps had to be ground before use. In the 1990s, pitch is stored in tanks heated by superheated steam or circulating hot-oil coils and transported in fiquid form in insulated rad, road tankers, or ships. When transport as a hot fiquid is not feasible, not acceptable by the customer, or for small amounts, the pitch is converted into a dust-free particulate form, ie, short rods termed pencils, pastilles, or flakes. 

Tanks cool and partially freeze solids form a layer of self-insulation. This complex case, which has been known to occur with heavy hydrocarbons and mixtures of hydrocarbons, has been discussed by Stnhlbarg [Pet. Refiner,. 38, 143 (Apr. 1, 1959)]. The contents in the center of snch tanks have been known to remain warm and liquid even after several years of cooling. 

There are two work terms to consider when a nucleus forms from the liquid. Equations (6.1) and (6.2) show that work of the type AH (T, - T)/T, is available to help the nucleus form. If AH is expressed as the latent heat given out when unit volume of the solid forms, then the total available energy is (4/3)ot AH (T, - T)/T, . But this is offset by the work 4 rr ysL needed to create the solid-liquid interface around the crystal. The net work needed to form the crystal is then... 

The physical state of the fuel for a combustion process dictates the type of system to be used for burning. A fuel may be composed of volatile material, fixed carbon, or both. The volatile material bums as a gas and exhibits a visible flame, whereas the fixed carbon burns without a visible flame in a solid form. If a fuel is in the gaseous state, such as natural gas, it is very reactive and can be fired with a simple burner. 

Since the structure and properties of fullerene solids are strongly dependent on the structure and properties of the constituent fullerene molecules, we first review the structure of the molecules, which is followed by a review of the structure of the molecular solids formed from Ceo, C70 and higher mass fullerenes, and finally the structure of Cgo crystals. 

In solid form, the natural rubber is graded according to the content of dirt remaining from the precipitation of latex at the plantation. Eight basic NR types have been traditionally recognized internationally. Only the so-called ribbed smoked sheets and the pale crepes are normally used for adhesives. The predominant grade system, the Standard Malaysian Rubber system, has been used since 1965. 

Forms of SBR. SBR is sold for adhesive manufacturing as latices or in solid form. 

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