Freezing point, DESs

The observed melting point of camphor is often low. Look up the molal freezing-point-de-pression constant K for camphor and calculate the expected depression of the melting point of a quantity of camphor that contains 0.5 molal impurity. Hint Look in a general chemistry book under "freezing-point depression" or "colligative properties of solutions."... 

Sweetness is primarily a function of the levels of dextrose and maltose present and therefore is related to DE. Other properties that increase with increasing DE value are flavor enhancement, flavor transfer, freezing-point depression, and osmotic pressure. Properties that increase with decreasing DE value are bodying contribution, cohesiveness, foam stabilization, and prevention of sugar crystallization. Com symp functional properties have been described in detail (52). 

De Luca et al. [1.48] showed, that the addition of 5 % tertiary butyl alcohol (tBA) to aqueous sucrose and lactose solutions (up to 40 %) resulted in a frozen matrix, which could be easily freeze dried. De Luca demonstrated by DSC that the melting point rose distinctly (with 60 % solution to -10 °C), but the endothermic of melting returned to 25 %, indicating that not much water had frozen. In solutions with 5 % tBA the exothermic of crystallization became more visible and the melting of tBA could be recognized. 

Above the freezing point of silver, Tgq is defined in terms of a defining fixed point and the Planck radiation law, and optical pyrometers are frequently used as temperature probes. The Comite Consultatif de Thermometrie gives a thorough discussion of the different techniques for approximation of the international temperature scale of 1990 [2, 4],... 

L. C. de Coppet found that the freezing point of a sat. soln. of the salt, containing 62 2 grms. of salt in 100 grms. of water, is —19-05° and, according to F. Guthrie, when soln. of different cone, are cooled, the solid phase separating at different temp, is as follows ... 

For density and freezing-point determinations on aqueous solutions of the acid, see de Coninok, Bull. Acad. roy. Bely., 1905, p. 150 Rosenheim and Krause, Zeitsch. anorg. Chem., 1921, ri8, 177 Manohot and Ortner, ibid., 1922, 120, 302. 

As to other organic substances in this context, special mention must be made of glycoproteins, which prevent blood from freezing in Arctic and Antarctic fish (De Vries, 1970 Hochachka and Somero, 1973). Glycoprotein, composed of repeated subunits of alanine and threonine bound to a disaccharide derivative of galactose, is an antifreeze agent (DeVries, 1971 Shier et al., 1972). It impedes crystal formation in blood and lowers the freezing point to -1.8°C, the lowest... 

As a first approximation, the stresses for the solid, ice and gel water can be formulated with the help of a linearized Hookean type law, where the depression of the gel water below the macroscopic freezing point of water must be considered. This can be done by including the micro-ice-lens model of Set-zer [1] in the constitutive relations for the aforementioned stress tensor. The gas phase can be described as an ideal gas. Concerning the constitutive assumptions for the liquid stresses, the heat flux and the interactions, the reader is referred to de Boer et al. [4], There a ternary model for the numerical simulation of freezing and thawing processes is discussed. 

Another possibility to establish the traceability of amount of substance measurements is to use the following primary methods indicated by the Comite Consultatif pour la Quantite de Matiere (CCQM) isotope dilution with mass spectrometry, coulometry, gravimetry, titrimetry, determination of freezing-point depression, and methods which provide a direct traceability to SI units. 

All aqueous solutions have maxima of density, which occur at temperatures lower than 4°. The temperature of maximum density is lowered like the freezing point when a substance is dissolved in water, but to a much greater degree. According to the investigations of de Coppet, the lowering of the temperature of maximum density in salt solutions is proportional to their molecular concentration but the molecular lowering varies for each salt. 

Corn syrup is used in almost every type of confection to control sucrose and dextrose crystallization, which may lead to crumbling. Corn syrup in appropriate proportion with sucrose and dextrose allows the formation of an amorphous glass and produces a candy with the desirable appearance. The following physical properties of corn syrup are extremely important in the preparation of medicated candies density, dextrose equivalent (DE), hygroscopicity, sugar crystallization, viscosity, freezing-point depression, and osmotic pressure. 

Mercier DE, Feld RD, Witte DL. Comparison of dewpoint and freezing point osmometry. Amer J Med Technol 1978 44 1066-9. 

At that time van t Hoff made his famous comparison between solutions and gases. He stated that solutes in dilute solution were governed by the same equation of state which applies to gases pv = RT, where p represents the osmotic pressure of the solution instead of the gas pressure. The behavior of nonelectrolytes is well described by this rule. The measurements of Raoult have shown that the lowering in freezing point of solvents is independent of the nature of the solute, and is determined only by the molecular concentration of the solute. Further investigations by Pfeffer, M. Traube, and Hugo de... 

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