Boil-off effect

The costs associated with liquefied hydrogen storage are determined by the production rate, storage time, and boil-off rate. Equation (5) is used to determine the net production accounting for the losses incurred from the boil-off effect... 

A realistic model of a solution requires at least several hundred solvent molecules. To prevent the outer solvent molecules from boiling off into space, and minimizing surface effects, periodic boundary conditions are normally employed. The solvent molecules are placed in a suitable box, often (but not necessarily) having a cubic geometry (it has been shown that simulation results using any of the five types of space filling polyhedra are equivalent ). This box is then duplicated in all directions, i.e. the central box is suiTounded by 26 identical cubes, which again is surrounded by 98 boxes etc. If a... 

Determination of thallium as chromate Discussion. The thallium must be present in the thallium(I) state. If present as a thallium(III) salt, reduction must be effected (before precipitation) with sulphur dioxide the excess of sulphur dioxide is boiled off. 

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

Later their use in the pretreatment of cotton was described, i.e., mercerizing [169], boiling off [8,170], and bleaching [170,171], For wool washing and wool treatment ether carboxylates have also been mentioned the detergent effect is better than that of the corresponding nonionics, a pleasant feeling is achieved and there is no corrosion on metal [172],... 

The possible benefits of prescouring to remove such contaminants should also be considered. Alkaline pretreatments, including boiling off of cotton, have a profound effect on AOX values after chlorite bleaching (Tables 10.21 and 10.22). It can be beneficial, from the viewpoint of both AOX and whiteness, to follow a chlorite bleach with a peroxide treatment. Linen yarns after an alkaline scour and chlorite bleach gave a whiteness value of 63.9 with an unacceptably high AOX value of 8.0 ppm. These results were improved to 78.5 and 1.2 ppm respectively after peroxide treatment [224]-... 

Table 10.22 Effect of desize and boil-off of cotton on AOX and whiteness values before and after chlorite bleaching [224]... 

Performing a simple distillation experiment is every chemist s delight. We gently warm a mixture of liquids, allowing each component to boil off at its own characteristic temperature (the boiling temperature r(boii)). Each gaseous component cools and condenses to allow collection. Purification and separation are thereby effected. 

R. A. Marcus I understand that the observed effect of a decrease in rate constant k(E) with increasing cluster size at a fixed E was not due to a boiling off of the hexane molecules (and hence to a reduced E), but I refer to my colleague, Ahmed Zewail, for an answer to your question. 

Suggestion 3 has limited practicality. It can only be effective after work on the vacuum line is complete and you wish to shut down the system. This plan will not help vacuum lines left unattended and/or whose liquid nitrogen has boiled off. Regardless, if frozen oxygen boils off faster than can be released by the vent, the results would be the same as if no vent were available. Thus, the potential for disaster is still present. 

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