Boiling point, correction

In order to obtain boiling point corrections for distillation under reduced pressure the following expressions are used ... 

H. B. Hass and R. F. Newton, Handbook of Chemistry and Physics, 64th ed., (Cleveland, Ohio Chemical Rubber Publishing Company, 1484-84), p. D-186. This information is presented in earlier editions and is indexed under, "boiling points, correction to slandnrd pressure. ... 

Bitter almond green, 322. Boiling-point, corrections of, 32. Bomb-furnace, 61. 

Tl = normal boiling point corrected to K = 12, °R T = absolute temperature, °R... 

Those checking the reference from where this technique was developed will find mention that it should only be applied to pure hydrocarbons and narrow-boiling range petroleum fractions. However this restriction applies primarily to the conversion between the true normal boiling point (Ti,) and the boiling point corrected to a Watson K of 12 (T ). The procedure for calculating PCT does not involve this conversion and experience shows that the resulting formula works well. 

Vapor Pressure and Boiling Point Corrections. The vapor pressure or tendency of a liquid to vaporize is involved in condensation, vaporization, fractionation, etc., computations as well as the correction of boiling points from one pressure to another. Figs. 5-25 and 5-26 are the result... 

Fig. 5-27. Vapor pressure and boiling-point corrections for normal paraffin hydrocarbons and petroleum fractions.

For distillations conducted at atmospheric pressure, the barometric pressures are rarely exactly 760 mm. and deviations may be as high as 20 mm. To correct the observed boiling point to normal pressiu e (760 mm.), the following approximate expression may be used ... 

The comparatively inexpensive long-scale thermometer, widely used by students, is usually calibrated for complete immersion of the mercury column in the vapour or liquid. As generally employed for boiling point or melting point determinations, the entire column is neither surrounded by the vapour nor completely immersed in the liquid. The part of the mercury column exposed to the cooler air of the laboratory is obviously not expanded as much as the bulk of the mercury and hence the reading will be lower than the true temperature. The error thus introduced is not appreciable up to about 100°, but it may amount to 3-5° at 200° and 6-10° at 250°. The error due to the column of mercury exposed above the heating bath can be corrected by adding a stem correction, calculated by the formula ... 

Repeat the boiling point determination with the following pure liquids (a) carbon tetrachloride, A.R. (77°) (6) ethylene dibromide (132°) or chlorobenzene (132°) (c) aniline, A.R. (184-6°) and (d) nitrobenzene, A.R. (211°). An air condenser should be used for (c) and (d). Correct the observed boiling points for any appreciable deviation from the normal pressure of 760 mm. Compare the observed boiling points with the values given in parentheses and construct a calibration curve for the thermometer. Compare the latter with the curve obtained from melting point determinations (Section 111,1). 

In addition to the orthodox method, just described, for the determination of the boiling points of liquids, the student should determine the boiling points of small volumes (ca. 0 5 ml.) by Siwolobofifs method. Full details are given iri Section 11,12. Determine the boiling points of the pure liquids listed in the previous paragraph. Observe the atmospheric pressure and if this differs by more than 5 mm. from 760 mm., correct the boiling point with the aid of Table II,9,B. Compare the observed boiling points with the accepted values, and draw a calibration curve for the thermometer. 

As a starting point for identifying candidate solvents, all compounds having boiling points below that of any component in the mixture to be separated should be eliminated. This is necessary to yield the correct residue curve map for extractive distillation, but this process implicitly rules out other forms of homogeneous azeotropic distillation. In fact, compounds which boil as much as 50°C or more above the mixture have been recommended (68) in order to minimize the likelihood of azeotrope formation. On the other hand, the solvent should not bod so high that excessive temperatures are required in the solvent recovery column. 

The use of CO is complicated by the fact that two forms of adsorption—linear and bridged—have been shown by infrared (IR) spectroscopy to occur on most metal surfaces. For both forms, the molecule usually remains intact (i.e., no dissociation occurs). In the linear form the carbon end is attached to one metal atom, while in the bridged form it is attached to two metal atoms. Hence, if independent IR studies on an identical catalyst, identically reduced, show that all of the CO is either in the linear or the bricked form, then the measurement of CO isotherms can be used to determine metal dispersions. A metal for which CO cannot be used is nickel, due to the rapid formation of nickel carbonyl on clean nickel surfaces. Although CO has a relatively low boiling point, at vet) low metal concentrations (e.g., 0.1% Rh) the amount of CO adsorbed on the support can be as much as 25% of that on the metal a procedure has been developed to accurately correct for this. Also, CO dissociates on some metal surfaces (e.g., W and Mo), on which the method cannot be used. 

Determinaj fcioii of tliB Boiling-point.—A correct determination of the boiling-point of a liquid is made with a standard... 

This correction may be avoided by using shoit (Anschutz) thermometers, in which the mercury thread is entirely immersed in the vapour. A rough correction for points above 100° may be made by detei mining the boiling points of pure organic substances, such as naphthalene, 2i6 6°, c. 

Boiling-point method, 37 determination of, 58 correction for, 59 / 1 iroinacetanilicle, 152 Bromacetic acid, 8g Broiiiaceiyl bromide, 89 Bromuhenzene, 140 y /-Bromobenz.oic acid, 201 Brouiocresol, 165 / Bromoioluene, 167 Butyric acid, 99... 

Correction for boiling point, 59 Creatine, 132 -Cresol, 164 Cryoscopic method, 32 Crystallisation, 52 Cuprous chloride, 166 Cyclohexanol, 181... 

The retention gap method (1, 2) represents the best approach in the case of qualitative and quantitative analysis of samples containing highly volatile compounds. The key feature of this technique is the introduction of the sample into the GC unit at a temperature below the boiling point of the LC eluent (corrected for the current inlet pressure), (see Eigure 2.2). This causes the sample vapour pressure to be below the carrier gas inlet pressure, and has two consequences, as follows ... 

Correction to Volumetric Average Boiling Point, VABP, Deg. F... 

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