How to use Boiling-points in a sentence
Under such conditions, distillation takes place at higher temperatures than the normal boiling-points of the constituent hydrocarbons of the oil, and a partial cracking results.
Theoretical considerations as to how far Kopp was justified in choosing the boiling-points under atmospheric pressure as being comparable states for different substances now claim our attention.
As a general rule, compounds formed tive with a great evolution of heat have high boiling-points, and vice versa.
A factor of considerable importance in determining boiling-points of isomers is the symmetry of the molecule.
The nitro compounds are colourless, somewhat pleasant smelling liquids, which distil without decomposition and possess boiling points much higher than those of the isomeric nitrous esters.Advertisement
In all mercurial thermometers there is a slight depression of the ice-point after exposure to high temperatures; it is also not uncommon to find that the readings of two thermometers between the iceand boiling-points fail to agree at any intermediate temperature, although the iceand boiling-points of both have been determined together with perfect accuracy, and the intervening spaces have been equally divided.
The crude cresol obtained from tar cannot be separated into its different constituents by fractional distillation, since the boiling points of the three isomers are very close together.
Generally the components of a mixture will be vaporized in the order of their boiling-points; consequently if the condensates or "fractions" corresponding to definite ranges of temperature be separately collected, it is obvious that a more or less partial separation of the components will be effected.
Since many substances decompose either at, or below, their boiling-points under ordinary atmospheric pressure, it is necessary to lower the boiling-point by reducing the pressure if it be desired to distil them.
This method is adopted for substances which decompose at their boiling-points under ordinary pressure, and, generally, when it is desirable to work at a lower temperature.Advertisement
This method is particularly successful in the case of substances which cannot be distilled at their ordinary boiling-points (it will be seen in the following section that distilling with steam implies a lowering of boiling-point), and which can be readily separated from water.
The theory of fractional distillation, or the behaviour of liquid mixtures when heated to their boiling-points, is more complex.
Even at the boiling-points the discrepancies between different observers are frequently considerable.
Thus, as the atomic weight increases, the state of aggregation changes from that of a gas in the case of fluorine and chlorine, to that of a liquid (bromine) and finally to that of the solid (iodine); at the same time the melting and boiling points rise with increasing atomic weights.
The boiling points of the normal alcohols increase regularly about for each CH, increment; this is characteristic of all homologous series of organic compounds.Advertisement
In 1867 Rees Reece, taking advantage of the fact that two vapours of different boiling-points, when mixed, can be separated by means of fractional condensation, brought out an absorption machine in which the distillate was very nearly anhydrous.
From the air or gas mixture, adsorption media preferentially adsorb components with high boiling points.
Down the group, the metals get more reactive, and the melting points and boiling points decrease.