Boiling-point Sentence Examples
The vaporization of a substance below its normal boiling-point can also be effected by blowing in steam or some other vapour; this operation is termed "distillation with steam."
Guldberg pointed out that for the most diverse substances the absolute boiling-point is about two-thirds of the critical temperature.
The colour, the boiling-point, the specific gravity and solubility in alcohol serve as most valuable adjuncts in the examination with a view to form an estimate of the genuineness and value of a sample.
The pressure in the refrigerator being reduced by the pump and maintained at such a degree as to give the required boiling-point, which is of course always lower than the temperature outside the coils, heat passes from the substance outside, through the coil surfaces, and is taken up by the entering liquid, which is converted into vapour at the temperature T i.
Owing to the fact that at temperatures between its melting and boiling point zinc has a strong affinity for iron, it is often contaminated by the scraper while being drawn from the condenser, as is shown by the fact that the scraper wears away rapidly.Advertisement
At a red heat rutile is produced, at the boiling point of zinc brookite, and of cadmium anatase.
The steam rising from the latter is passed into a similar pan, in which it circulates round another set of pipes, but as it could not bring the liquid in the latter to boil under ordinary conditions, the second pan is connected with a vacuum-pump so that the boiling-point of the liquid in this pan is lowered.
Recent researches have shown that the law originally proposed by Kopp - " That the specific volume of a liquid compound (molecular volume) at its boiling-point is equal to the sum of the specific volumes of its constituents (atomic volumes), and that every element has a definite atomic value in its compounds " - is by no means exact, for isomers have different specific volumes, and the volume for an increment of CH 2 in different homologous series is by no means constant; for example, the difference among the esters of the fatty acids is about 57, whereas for the aliphatic aldehydes it is 49.
Hence within narrow limits Kopp's determinations were carried out under coincident conditions, and therefore any regularities presented by the critical volumes should be revealed in the specific volumes at the boiling-point.
It may he shown theoretically that the absolute boiling-point is proportional to the molecular volume, and, since this property is additive, the boiling-point should also be additive.Advertisement
The introduction of negative groups into a molecule alters the boiling-point according to the number of negative groups already present.
An ethylenic or double carbon union in the aliphatic hydrocarbons has, apparently, the same effect on the boiling-point as two hydrogen atoms, since the compounds C 0 H 2 „ +2 and CoH2n boil at about the same temperature.
This tube was placed in an outer tube containing the liquid to be experimented with; the liquid is raised to its boiling-point, and then hermetically sealed.
Saturated steam is steam in contact with liquid water at a temperature which is the boiling point of the water and condensing point of the steam; superheated steam is steam out of contact with water heated above this temperature.
These limits may be set down as from a little above the freezing point of water to a little below the boiling point.Advertisement
If zinc be heated to near its boiling-point, it catches fire and burns with a brilliant light into its powdery white oxide, which forms a reek in the air (lana philosophica, " philosopher's wool").
The next higher members of the series are liquids of low boiling point also readily soluble in water, the solubility and volatility, however, decreasing with the increasing carbon content of the molecule, until the highest members of the series are odourless solids of high boiling point and are insoluble in water.
Almost all these springs are at a very hot temperature, often at boiling point.
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 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.Advertisement
A liquid boils when its vapor pressure equals the superincumbent pressure; consequently any process which diminishes the external pressure must also lower the boiling-point.
At one time it was thought that these mixtures of constant boiling-point (an extended list is given in Young's Fractional Distillation) were definite compounds.
The above theory, coupled with such facts as the variation of the composition of the constant boiling-point fraction with the pressure under which the mixture is distilled, the proportionality of the density of all mixtures to their composition, &c., shows this to be erroneous.
The vapours rising from the still traverse a tall vertical column, and are then conveyed through a series of bulbs placed in a bath kept at the boiling-point of the most volatile constituent.
Another question to which he gave much attention was the connexion of the boiling-point of compounds, organic ones in particular, with their composition.Advertisement
Other methods consist in determining the vapour tension by means of the vaporimeter of Geissler, or the boiling point by the ebullioscope.
In general these compounds are decomposable by heat, but some of them, such as those of gold, silver, copper and the alkali metals, even when heated above the boiling point of mercury retain mercury and leave residues of definite composition.
In 1826 Dumas devised a method suitable for substances of high boiling-point; this consisted in its essential point in vaporizing the substance in a flask made of suitable material, sealing it when full of vapour, and weighing.
It is to be noted, however, that this method is applicable to substances of any boiling-point (see below).
To use the apparatus, a liquid of suitable boiling-point is placed in the jacket and brought to the boiling-point.
Hecker took the opportunity of a voyage from Hamburg to La Plata, and in 1904 and 1905 of voyages in the Indian and Pacific Oceans to determine the local attraction over the ocean by comparing the atmospheric pressure measured by means of a mercurial barometer and a boiling-point thermometer, and obtained results similar to Scott Hansen's.
Further Physical Properties of Sea-water.---The laws of physical chemistry relating to complex dilute solutions apply to seawater, and hence there is a definite relation between the osmotic pressure, freezing-point, vapour tension and boiling-point by which when one of these constants is given the others can be calculated.
Fine lakes and waterfalls, innumerable pools, in temperature from boiling-point to cold, geysers, solfataras, fumaroles and mud volcanoes still attract tourists in large numbers.
A third oil was obtained by heating the liver-residues to above the boiling-point of water, whereupon a black product, technically called "brown oil," separated.
Similar is the behaviour of the fused dry salt at a dull red heat; it acts on silicates, titanates, &c., as if it were sulphuric acid raised beyond its natural boiling point.
Andrews's conception of the critical temperature of gases by defining the absolute boiling-point of a substance as the temperature at which cohesion and heat of vaporization become equal to zero and the liquid changes to vapour, irrespective of the pressure and volume.
If a more dilute acid than this be distilled, water passes over in excess and the residue in the retort reaches the above composition and boiling point; on distillation of a stronger acid, excess of acid passes into the distillate and the boiling point rises until the values of the constant boiling mixture are reached.
Since this has not been done we must adopt the approximate rule that the volume at absolute zero is proportional to that at the boiling-point.
According to Rabuteau the toxic properties of the higher alcohols increase with their molecular weight and boiling point.
But in many cases it is more readily determined by observing the rise of the boiling-point or the depression of the freezing-point of the solution.
For the rise in the boiling-point, we have by Clapeyron's equation, dp/do = L/ov, nearly, neglecting the volume of the liquid as compared with that of the vapour v.
If dp is the difference of vapourpressure of solvent and solution, and do the rise in the boiling-point, we have the approximate relation, n/N = d p/p = mLdo/Ro 2, Raoult's law,..
The highest pressures recorded for cane-sugar are nearly three times as great as those given by van't Hoff's formula for the gas-pressure, but agree very well with the vapour-pressure theory, as modified by Callendar, provided that we substitute for V in Arrhenius's formula the actual specific volume of the solvent in the solution, and if we also assume that each molecule of sugar in solution combines with 5 molecules of water, as required by the observations on the depression of the freezing-point and the rise of the boiling-point.
The approximate equation of Rankine (23) begins to be I or 2% in error at the boiling-point under atmospheric pressure, owing to the coaggregation of the molecules of the vapour and the variation of the specific heat of the liquid.
Vapour density determinations indicate that dissociation occurs when the vapour is heated above the boiling point.
The lead sulphate, obtained as described above and dissolved in ammonium acetate, is acidulated with acetic acid diluted with hot water and heated to boiling-point.
Lead can be used for the purpose only when the boiling-point of the acid is reduced by means of a vacuum - a plan which has not met with much success.
Coal gas, being a mixture of gases and vapours of liquids having very varying boiling points, must necessarily undergo physical changes when the temperature is lowered Vapours of liquids of high boiling point will be condensed more quickly than those having lower boiling points, but condensation of each vapour will take place in a definite ratio with the decrease of temperature, the rate being dependent upon the boiling point of the liquid from which it is formed.
It also dissolves in alcohol and ether; boiling point determinations of the molecular weight in these solutions point to the formula FeCl3.
Of the primary, secondary and tertiary alcohols having the same empirical formula, the primaryhave the highest, and the tertiary the lowest boiling point; this is in accordance with the fairly general rule that a gain is symmetry is attended by a fall in the boiling point.
They also investigated certain hydrocarbons occurring in the high boiling point fraction of the coal tar distillate and solved the constitution of phenanthrene.
Since that time the development of the petroleum industry in all parts of the world and the large quantities of low boiling-point hydrocarbons - naphtha - obtained from the petroleum fields, and also the improvements in the apparatus employed, have raised this system of extraction to the rank of a competing practical method of oil production.
The principle of the absorption process is chemical or physical rather than mechanical; it depends on the fact that many Absorp- vapours of low boiling-point are readily absorbed in water, and can be separated again by the application of heat.
In each case, the alkene has a boiling point which is a small number of degrees lower than the corresponding alkane.
Where you have isomers, the more branched the chain, the lower the boiling point tends to be.
In a wide, heavy-based saucepan gently heat the milk to boiling point.
When the strands are heated in a salt solution to just below boiling point then rapidly cooled they bond together to form a tetrahedron.
A liquid boils when its vapour pressure equals the superincumbent pressure (see Vaporization); consequently any process which diminishes the external pressure must also lower the boiling-point.
Chlorination in the cold gives orthoand para-chlortoluenes, but at the boiling point the side chain is substituted (see Benzaldehyde).
My boiling point was finally exceeded just this year, when someone with a stick of " sidewalk chalk " scrawled JESUS LOVES YOU !
In districts where the water is of a " hard nature," that is, contains bicarbonate of lime in solution, the interior of the boiler cylinders, tanks and pipes of a hot water system will become incrusted with a deposit of lime which is gradually precipitated as the water is heated to boiling point.
The " cracking " process, whereby a considerable quantity of the oil which is intermediate between kerosene and lubricating oil is converted into hydrocarbons of lower specific gravity and boiling-point suitable for illuminating purposes, is one of great scientific and technical interest.
The cracking process practically consists in distilling the oils at a temperature higher than the normal boiling point of the constituents which it is desired to decompose.
The graduation of a thermometer is determined by the freezing-point and the boiling-point of water, the interval between these being divided into a certain number of degrees, representing equal increases of temperature.
Reduce the heat after it reaches the boiling point.
Simmer over low heat until it just reaches the boiling point.
In a double boiler, slowly heat the heavy cream; simmer over low heat just to the boiling point.
In a double boiler, slowly heat the heavy cream and butter, simmering over low heat just to the boiling point.
Kopp, begun in 1842, on the molecular volumes, the volume occupied by one gramme molecular weight of a substance, of liquids measured at their boiling-point under atmospheric pressure, brought to light a series of additive relations which, in the case of carbon compounds, render it possible to predict, in some measure, the cornposition of the substance.