Boiling in an Open Vessel

Mechanistically, then, the system pressure establishes the temperature, and the heat flux to the system establishes the vapor boil-off rate. 

the constraint on the system, namely that the fluid is boiling, states that 

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If an organic solvent is used, boiling in an open vessel is obviously not permissible, as the operation would be wasteful in all cases, and dangerous with an inflammable solvent. 

Experiment.—Ordinary water is boiled in an open vessel the water is changed to a vapour which disappears, and a white powdery earth remains in the vessel. 

The presence of hypochlorous acid in the aq. soln. is shown by leading a current of mixed air and chlorine through a flask of water between 90° and 95°, and condensing the products in a cooled flask. Hypochlorous acid is volatilized and condensed. S. U. Pickering18 also showed in 1880 that when an aq. soln. of chlorine is boiled in an open vessel, a dil. soln. of hydrochloric acid remains after the expulsion of the free chlorine, and A. Richardson (1903) has shown that when chlorine water is distilled, the hydrochloric acid is eq. to the hypochlorous acid in the distillate. The presence of chlorides, hypochlorous, hydrochloric, and other acids diminish the hydrolysis in virtue of the mass action law Cl2+H2O HCl+HOC1. In consequence, the apparent solubility of chlorine will be diminished, since less will be needed for establishing equilibrium Cl2 +H2O HCl+HOCl—unless the result be obscured by a reaction between the acid and the chlorine such as must occur when the soln. contains over about a gram of HC1 per 100 c.c. of hydrochloric acid. 

The oxidation of ammonia to nitrate is spontaneous and no losses are observed when the oxidation is performed in a sealed bottle 80 % of the ammonia is retained after boiling in an open vessel. The nitrate content of the sample after oxidation is finally determined after conversion into nitrite and, since the method for the determination of nitrite is very sensitive, the volume of the initial sample required is only 5-20 mL. 

If a solution like that at H is boiled in an open vessel, on the other hand, with the vapors escaping into the atmosphere, since the vapor is richer in the more volatile substance, the liquid residue must therefore become leaner. The temperature and composition of the saturated residual liquid therefore move along the lower curve toward as the distillation proceeds. 

Filling may be conducted at low temperature or high pressure and requires specialized equipment. Low-temperature filling is carried out at a temperature substantially lower than the boiling point of the propellant to allow manipulation at room temperature in an open vessel. Pressure filling is conducted in a sealed system from which the propellant is dispensed at its equilibrium vapor pressure at room temperature through the valve of the container [33]. 

Alternatively, microwave-assisted synthesis has been carried out using standard organic solvents under open-vessel conditions. If solvents are heated by microwave irradiation at atmospheric pressure in an open vessel, the boiling point of the solvent typically limits the reaction temperature that can be achieved. In order to none-... 

On account of the low boiling point care must be taken during the experiment that the preparation is never left for any length of time in an open vessel. Moreover, the finished preparation which is to be used for further work (cf. ethylbenzene) should not be kept in a thin-walled flask, least of all in summer, but should be stored in a thick-walled reagent bottle. Yield, 70-80 g. 

In Chapter VI, I said that when an alchemist boiled water in an open vessel, and obtained a white earthy solid, in place of the water which disappeared, he was producing some sort of experimental proof of the justness of his assertion that water can be changed into earth. Lavoisier began his work on the transformations of matter by demonstrating that this alleged transmutation does not happen and he did this by weighing the water, the vessel, and the earthy solid. 

Solid samples are digested with suprapure sub-boiled HN03 to avoid contamination in an acid mixture using HF, HC1 or 4 (e.g., in an open vessel directly or in a closed vessel by microwave induced digestion). The sample digestion of difficult-to-dissolve sample material in closed vessels,... 

In preparations wherein the dienophile could undergo side reaction with the solvent alcohol, either benzene or toluene usually proved to be a satisfactory reaction medium lower-boiling solvents, such as ether, chloroform, or acetone, were avoided by the submitters because of the high reaction pressures developed. If the dienophile is highly reactive and not appreciably volatile below about 200°, the reaction may be successfully conducted without solvent by careful fusion of an intimate mixture of the reactants in an open vessel.6-9 Caution Such fusions should be performed in a good fume hood because of the copious evolution of sulfur dioxide. 

A liquid mixture containing 40.0 mole% methanol and 60.0 mole% l-propanol is placed in an open vessel and heated slowly. Estimate the temperature at which the mixture begins to boil. List assumptions made in your calculations. If heat is supplied continuously, how will the liquid temperature and composition change with time ... 

Salicylic add is prepared technically on the large scale. Since it is an excellent antiseptic, it finds extensive application in preventing fermentation, for the preservation of meat, for the disinfection of wounds. It may easily be recognised, since its water solution gives a violet colour with ferric chloride in this action it differs from the para- and meta-modifications. It is volatile with steam for this reason it must not be boiled too long in an open vessel when it is to be recrystallised. All ortho-oxycarbonic adds show this property the... 

Boil them to dryness in an open iron vessel, frequently stirring the mixture with an iron spatula. Wash out all the uncombined acid, with water, and dry the residuum to which add an equal weight of supertartrate of potass, dissolved in water then boil in an iron vessel, filter, and set by to crystallize. The evaporation, filtration, and crystallization may be repeated with the fluid which remains but if the crystals are not perfectly clear, they must be dissolved in water and recrystallized. 

Sodium hydroxide 30% aqueous solution. Boil the solution for 10-15 min in an open vessel to remove traces of ammonia. 

Nitrogen-wash solution. Dissolve 2 g of KMn04 and 4 g of Hg(N03)2 in 100 ml of dilute HNO3 (1+99) boil the solution in an open vessel for 20 min, then cool. 

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