Boiling-point determinations

Distillation. If the impurities in a liquid are non-volatile, the liquid may be purified by direct distillation, the impurities remaining in the distilling-flask. This process is therefore essentially the same as a simple distillation for boiling-point determination, and has been already described on pp. 7-9. 

Full experimental details for the determination of melting and boiling points are given in Sections 11,10 and 11,11 respectively. The Tables II, 9, A and II, 9, B list suitable substances for the cabbration of thermometers by melting point or boiling point determinations respectively. Substances which are bracketed are alternative to each other. It need hardly be emphasised that only compounds of the highest purity should be employed. 

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). 

If time is limited, the boiling point determinations by the distilling flask method for these liquids may be omitted. 

Siedepunkt, m. boiling point, -bestimmuug, /. boiling-point determination, -(s)erhohimg, /. boiling-point elevation. 

For a specific paint application, a mixture of solvents is needed. The mixture is going to be identified by its ability to mix with water (total miscibility), normal boiling point (determines the solvent evaporation rate), the solubility parameter (determines if it is soluble in the paint) and molecular weight (size the candidate molecule). 

Effects of Thermal Energy Thermal conductivity Melting and boiling point determinations Ice point-humidity instrumentation, among others Dew point-humidity instrumentation, among others Vapor pressure Fractionation C liro matography Tliermal expansion... 

TESTING (Chemical). Identification of a substance by means of reagents, chromatography, spectroscopy, melting and boiling point determination, etc. 

Simulated Distillation of Bitumen Sample. The boiling-range distribution of the recovered bitumen was determined by simulated distillation gas-liquid chromatography using the procedure of Poulson et al. (15). Boiling points are determined by calibration with a mixture of n-paraffins ranging from Cn to C42. The upper limit for boiling point determination in this analysis is about 540°C (1000°F). 

The chemicals used for boiling point determinations are flammable. Be sure all Bunsen burner flames are extinguished before starting this part of the experiment. 

Do as many boiling point determinations as required by your instructor. 

A student in New York City carried out a boiling point determination for cyclohexane (b.p. 81°C) according to the procedure in this laboratory manual. Will this student s observed boiling point be the same as the value obtained by another student in Denver, Colorado (nicknamed the Mile-High City ) Will it be lower or higher Explain your conclusion. 

The specific volume at the boiling-point, determined by the method of Ramsay,2 was 0-6744 c.c. The corresponding atomic volume2 is 20-9 0-4. This constant thus lies between 20 and 21, with a tendency to diminish on keeping the phosphorus at this boiling temperature, owing to the formation of the denser Pj molecules, which are shown by the cherry-red colour of the liquid. 

The determination of the boiling point has already been mentioned briefly in the discussion on distillation, and here we shall deal with the corrections which may be necessary. It is well known that the boiling point is dependent on the pressure and therefore the pressure must be taken into account in an accurate boiling point determination. This correction is not very large, not exceeding about 2°C., at barometric pressures above 700 mm. A larger error under some conditions... 

The flash point and boiling point determine the class of a liquid. However, these should not be the only criteria used to determine the hazards of a liquid. Many other factors should also be considered for the proper use and storage of hazardous liquids. These factors include ignition temperature, lower explosive limit (LEL) or upper explosive limit (UEL), vapor pressure, specihc gravity, and vapor density. 

The boiling-point determined by Ramsay and Young s method is defined as the highest temperature attainable by a liquid under a given pressure of its own vapour when it evaporates only at its free surface, and the heat of evaporation reaches the liquid surface from outside, and not inside the liquid. The question whether this temperature is identical with what is commonly known as the boiling-point of a liquid is one which can be answered only by experiment, and the decision has produced a good deal of controversy it was finally decided in the affirmative. ... 

Platinum Pentafluoride.—This is best prepared by the medium-temperature fluorination of platinum dichloride.i It is a deep red solid which melts at 80 to a viscous red liquid. The ready disproportionation, 2PtFg— PtFg -f- PtF, prevents purification by distillation. Reliable boiling-point determination is not possible and our earlier value must be rejected, since that observed was of tetrafluoride dissolved in pentafluoride. 

Table 3 shows heats of vaporization and boiling points determined from vapor pressure measurements below 110 °C. It is reasonable to assume that tars under these conditions can be considered fresh i.e. no significant condensation type reactions had taken place. 

B) Capillary for boiling-point determination, according to Emich... 

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