Crystalline solids hardness

In a 500 ml. three-necked flask, fitted with a reflux condenser and mechanical stirrer, place 121 g. (126-5 ml.) of dimethylaniline, 45 g. of 40 per cent, formaldehyde solution and 0 -5 g. of sulphanilic acid. Heat the mixture under reflux with vigorous stirring for 8 hours. No visible change in the reaction mixture occurs. After 8 hours, remove a test portion of the pale yellow emulsion with a pipette or dropper and allow it to cool. The oil should solidify completely and upon boiling it should not smell appreciably of dimethylaniline if this is not the case, heat for a longer period. When the reaction is complete, steam distil (Fig. II, 41, i) the mixture until no more formaldehyde and dimethylaniline passes over only a few drops of dimethylaniline should distil. As soon as the distillate is free from dimethylaniline, pour the residue into excess of cold water when the base immediately solidifies. Decant the water and wash the crystalline solid thoroughly with water to remove the residual formaldehyde. Finally melt the solid under water and allow it to solidify. A hard yellowish-white crystalline cake of crude base, m,p. 80-90°, is obtained in almost quantitative yield. RecrystaUise from 250 ml. of alcohol the recovery of pure pp -tetramethyldiaminodiphenylmethane, m.p. 89-90°, is about 90 per cent. 

Below Tg the material is hard and rigid with a coefficient of thermal expansion equal to roughly half that of the liquid. With respect to mechanical properties, the glass is closer in behavior to a crystalline solid than to a... 

In chemicals like salol the molecules are elongated (non-spherical) and a lot of energy is needed to rotate the randomly arranged liquid molecules into the specific orientations that they take up in the crystalline solid. Then q is large, is small, and the interface is very sluggish. There is plenty of time for latent heat to flow away from the interface, and its temperature is hardly affected. The solidification of salol is therefore interface controlled the process is governed almost entirely by the kinetics of molecular diffusion at the interface. 

The present chapter is organized as follows. We focus first on a simple model of a nonuniform associating fluid with spherically symmetric associative forces between species. This model serves us to demonstrate the application of so-called first-order (singlet) and second-order (pair) integral equations for the density profile. Some examples of the solution of these equations for associating fluids in contact with structureless and crystalline solid surfaces are presented. Then we discuss one version of the density functional theory for a model of associating hard spheres. All aforementioned issues are discussed in Sec. II. 

Approximately 75% of all elements found on and in the Earth are metals. They are crystalline solids that at room temperature range from hard to butter-like soft to liquid (mercury). They are generally good conductors of heat and electricity as a result of the swarm of relatively free electrons in their outer shell that move without much resistance to other elements, particularly those with a dearth of electrons in their outer shells. In pure states, most metals have a shiny luster when cut. Those located at the far left of the table have only one electron in their outer shell. Therefore, they are very reactive and are not usually found in pure form. Instead, they are found in compounds, minerals, or ores that must be processed to extract the pure metal from the other elements in the compounds. 

Soft crystalline solid rhombic crystal pure salt is white but color may vary the color of the mineral barite may vary among red, yellow, gray or green depending on impurities density 4.50 g/cm refractive index 1.64 melts around 1,580°C decomposes above 1,600°C hardness 4.3 to 4.6 Mohs insoluble in water (285 mg/L at 30°C) and alcohol Ksp 1.1 x 10-i° soluble in concentrated sulfuric acid. 

Greenish blue to black crystalline solid hexagonal or cubic crystals dia-mond-like structure density 3.217g/cm3 exceedingly hard, Mohs hardness 9.5 sublimes at about 2,700°C dielectric constant 7.0 electron mobility >100 cm /volt-sec hole mobility >20cm2/volt-sec band gap energy 2.8 eV insoluble in water and acids solubilized by fusion with caustic potash. 

White crystalline solid orthorhombic structure refractive index 1.818 Mohs hardness 4.3 density 4.398 g/cm decomposes at 300°C forming zinc oxide practically insoluble in water, 10 mg/L at 15°C soluble in acids, alka-hs, and ammonium salt solutions. 

This opening chapter has introduced many of the principles and ideas that lie behind a discussion of the crystalline solid state. We have discussed in detail the structure of a number of important ionic crystal structures and shown how they can be linked to a simple view of ions as hard spheres that pack together as closely as possible, but can also be viewed as the linking of octahedra or tetrahedra in various ways. Taking these ideas further, we have investigated the size of these ions in terms of their radii, and... 

Borides Carbon boride, CB6. and silicon borides SiB3 and SiB6 are hard, crystalline solids, produced in ihe electric furnace magnesium boride, Mgi B2, brown solid, by reaction of boron oxide and magnesium powder ignited, forms boron hydrides with HC1 calcium boride, Ca3 B2, forms boron hydrides and hydrogen gas with IIC1. 

The nature of the bonds between the structural units of crystalline solids impart other physical properties to these solids. Metals are good conductors of electricity because metallic bonds allow a free flow of electrons. Covalent network, molecular, and ionic solids do not conduct electricity because their bonds do not provide for mobile electrons. Remember, however, that ionic solids in a water solution have free electrons and are good conductors of electricity. Metallic solids are malleable and ductile covalent network solids are brittle and hard. These differences in physical properties are caused by the chemical bonds between the units It is all in the bonds ... 

N-o-Bromobenzyl-N,N-dimethylamine (lOOg) and ethyl p-toluenesulfonate (94 g) were mixed and warmed to 50°-60°C after standing for either (a) a minimum of 96 hours at 15°-20°C or (b) a minimum of 18 hours at 50°-60°C and cooling to room temperature, a hard, crystalline mass was formed. Recrystallization of this product from acetone (2.0 ml/g of crude solid), followed by filtration and drying to 60°C gave N-o-bromobenzyl-N-ethyl-N,N-dimethylammonium p-toluenesulfonate as a white, crystalline solid, MP 97°-99°C. For this procedure it was necessary that the reactants were substantially colorless and of a high purity. 

What do they look like They may be crystalline solids, oils, waxes, plastics, elastics, mobile or volatile liquids, or gases, Familiar ones include white crystalline sugar, a cheap natural compound isolated from plants as hard white crystals when pure, and petrol, a mixture of colourless, volatile, flammable hydrocarbons. Isooctane is a typical example and gives its name to the octane rating of petrol. 

Myristic Acid occurs as a hard, white or faintly yellow, somewhat glossy, crystalline solid or as a white or yellow-white powder. It is obtained from coconut oil and other fats. Myristic Acid is practically insoluble in water, but it is soluble in alcohol, in chloroform, and in ether. 

PROP Bp 340-375°, flash p 383°F (COQ, d 1.44 30°. A series of technical mixtures consisting of many isomers and compounds that vary from mobile oily liquids to white crystalline solids and hard noncrystalline resins. Technical products vary in composition, in the degree of chlorination, and possibly according to batch (lARC 7,262,74). 

A simple substance such as water below its freezing point is a hard three-dimensional crystalline solid, and above its freezing point it is a low-viscosity Newtonian liquid. In the liquid state, the mechanical properties of such a substance are specified by its shear viscosity T], which is of course temperature- and pressure-dependent. 

In the present paper, we show that the quantum chemical (QC) simulation can be used as a simple and efficient tool for testing, whether known or theoretically predicted solid tends to form an amorphous phase. Two well-known substances, representing the extreme examples of crystalline and amorphous solids, namely lithium fluoride (LiF) and silica (Si02), are considered in order to illustrate the methodology. LiF is crystalline and hardly forms glassy state, while Si02 is known to form a number of non-crystalline isomorphes [4,5]. 

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