Melting point definition

Reference has already been made to the high melting point, boiling point and strength of transition metals, and this has been attributed to high valency electron-atom ratios. Transition metals quite readily form alloys with each other, and with non-transition metals in some of these alloys, definite intermetallic compounds appear (for example CuZn, CoZn3, Cu3,Sng, Ag5Al3) and in these the formulae correspond to certain definite electron-atom ratios. 

Primary aromatic amides are crystaUine sohds with definite melting points. Upon boiling with 10-20 per cent, sodium or potassium hydroxide solution, they are hydrolysed with the evolution of ammonia (vapour turns red htmus paper blue and mercurous nitrate paper black) and the formation of the alkah metal salt of the acid ... 

Type metal, another tin—antimony—lead alloy, is used primarily in reHef or letterpress printing. Antimony is added to increase hardness, minimize shrinkage, permit sharp definition, and reduce the melting point of the alloy. There has been a substantial decrease in the use of type metals as a result of the emergence of less expensive typesetting techniques. 

The above considerations indicate the complex nature of the hydrocarbons known as caryophyllene. For practical purposes, however, the compounds indicated are obtained of practically definite melting-points, and, in spite of the complicated isomerism existing amongst most of them, are useful for identification of the sesquiterpene or mixture of sesquiterpenes, occurring naturally and known as caryophyllene . 

The general temperature scale now in use is the Celsius scale, based nominally on the melting point of ice at 0°C and the hoiling point of water at atmospheric pressure at 100°C. (By strict definition, the triple point of ice is 0.01°C at a pressure of 6.1 mhar.) On the Celsius scale, absolute zero is -2 73.15°C. 

Compound 6 crystallizes from cyclohexane as colorless needles which have no definite melting point there is a change of color to yellow at 128-134 C and the compound then melts sharply at 187-189 r C. When the colorless form is kept for a long time or recrystallized from pyridine or dimethyl sulfoxide it is changed into the yellow modification of mp 187-189 C recrystallization from cyclohexane reverses the process. It has been suggested that the yellow stable form has structure 6A and that the colorless metastable compound is the tautomer 2-methyl-l//-pyrido[2,3-6][l, 4]diazepin-4(5//)-one (6B). There is evidence from 1H NMR spectroscopy that the isomeric pyridodiazepin-2-one, yellow crystals, mp 195—197 " C, exists as an inseparable mixture of the tautomers 4-methyl-l//-pyrido[2,3-6][l,4]diazepin-2(3//)-one (7 A) and 4-methyl-l H-pyrido[2,3-6][l, 4Jdiazepin-2(5//)-one (7B) in the ratio 1 3. 

Vicat hardness It is a determination of the softening point for TPs that have no definite melting point. The softening point is taken the temperature at which the specimen is usually penetrated to a depth of 1 mm2 (0.0015 in2) circular or square cross section, under a 1,000 g load. 

Such bodies have no definite melting-point, but pass continuously into the liquid state on heating. 

Hoffman takes Eq. (2.13) as the definition of bulk free energy per unit volume at the melting point, neglecting the fact that a surface contribution is also included. 

This discrepancy in definition of the melting point has not often been high-lighted, yet it is of considerable importance bearing in mind the accuracy claimed for the deduction of ae. 

Pure alkyl sulfuric acids are white crystalline solids with definite melting points but they are hygroscopic. Hygroscopicity increases as the chain length increases. Dodecyl, tetradecyl, hexadecyl, and octadecyl sulfuric acids were obtained by Maurer et al. [57] by chlorosulfation of the corresponding alcohols and the melting points obtained are shown in Table 2. 

Why do polymers not have definite molar masses How does the fact that polymers have average molar masses affect their melting points ... 

Polymers generally do not have definite molecular masses because there is no fixed point at which the chainlengthening process will cease. There is no fixed molar mass, only an average molar mass. Because there is no one unique compound, there is no one unique melting point, rather a range of melting points. 

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