Inflammability limits pressure

The vapour pressure of a liquid provides an essential safety parameter and it is mandatory that safety sheets contain these values (when they are known). This parameter is taken into account in some classification methods of inflammability risk. It enables one to determine the equilibrium vapour concentration of a liquid in air. This concentration can then be used to ascertain whether a working environment presents an inflammability risk (by reference to the inflammability limits) or a toxicity hazard (by comparison with the exposure values). 

Bromoethane was used in sterilisation equipment to make diethyl ether atmospheres fireproof. This method is inefficient since 31 % brominated derivative should be used. Inflammability data regarding bromoethane vary from one author to the next. It is most often agreed that this compound has very narrow inflammability limits (13.5-14.5%). The range is more critical under pressure and is thought to reach 8.6-20%. 

Fig. 12.—Effect of initial pressure on inflammability limits of methane-air mixtures. Data of Bolte and Newitt. [Compare Berl and Werner, Z. anyno. Chem. 40, 24S-S0 (1927).]...

The theoretical air required for the oxidation of toluene to benzoic add, 1.5 mols of oxygen per mol of tolnene, amounts to about 30 cn. ft. of air measured at 20° C. (6S° F.) and one atmosphere, per pound of toluene oxidized. Similarly, the theoretical air for oxidation to bcnzalcle-hyde amounts to 20 cu. ft. per pound of tolnene oxidized. The explosive limits of toluene at ordinary pressures and temperatures as measured in narrow tubes or small vessels are lower limit, 0.003375 lbs. toluene per cu. ft. air (296.5 cu. ft. air per lb. toluene) and upper limit, 0.01927 lbs. toluene per cu. ft. air (52 cu. ft. air per lb. toluene).1151 In the case of the lower aliphatic hydrocarbons as methane and ethane it is well known that the explosive or inflammability limits widen with rise in temperature so that it could well be expected that mixtures of toluene and air leaner than the one given for the lower limit and richer than the one for the upper limit would become inflammable as the temperature becomes higher. The same is true for increase in size of the explosion chamber. Hence, although theoretical mixtures of toluene and air for formation of benzaldehyde and benzoic acid lie on the rich side of the inflammable range,... 

When the branching of a chain is held in check by the diffusion of atoms or radicals to the walls there is normally a marked dependence of the inflammation limit upon the size of the containing vessel. Rate of chain-branching depends upon the volume of reacting gas removal by diffusion depends upon the surface area. Thus with increase in size there is a shift in favour of branching and an increase in explosive character. The critical pressure limit above which... 

Flashpoints (the reason for the plurality is explained in paragraph 1.3) have the advantage of being linked to the boiling point, the pressure and the lower explosive limit. This is the reason why flashpoints are such important parameters in the evaluation of the inflammability risk of a liquid or a solid. The measurement of flashpoints implies the existence of an ignition flame for the gaseous mixture. Nevertheless, contact of a suitable substance-air mixture with a hot surface can be sufficient to start the combustion of the mixture. The autoignition temperature is the parameter that determines the possibility that an inflammable material will combust in contact with a hot substance without the presence of a flame. 

Mixtures become inflammable when the vapour concentration lies between two limits called the lower explosive limit (LEL) and the upper explosive limit (UEL). These limits depend on numerous factors, especially temperature and pressure. 

Influence of Pressure.—Both the lower and the upper limits of inflammation are raised by increase of pressure. Hence the total effect upon the limits of inflammability is the algebraic sum of these two. In the case of methane the data 3 are as follow ... 

Cerebral edema occurs in response to a wide variety of insults, including ischemia, hypoxia, infection, and noninfectious inflammation. Shifts in brain water, which is the basis of the cellular swelling, are due to osmotic forces, and result in increases in intra- and extracellular spaces. A reasonable amount of tissue swelling can be tolerated in most parts of the body, however, the restrictions imposed by the rigid tentorium and bony skull cause life-threatening herniation with relatively small increases in the brain compartments. Two early anatomists, Monroe (1733-1817) and Kellie (1758-1829), recognized that increased intracranial pressure due to swelling in the cerebrospinal fluid (CSF), blood, or brain tissue compartments could increase intracranial pressure the concept of limited expansion capacity of the intracranial contents is called the Monroe-Kellie doctrine. 

Like fluorometholone, medrysone is a synthetic derivative of progesterone. As compared with prednisolone, dexamethasone, and fluorometholone, medrysone exhibits limited corneal penetration and a lower affinity for glucocorticoid receptors. In clinical use it appears to be the weakest of the available ophthalmic steroids. Medrysone can be useful for superficial ocular inflammations, including allergic and atopic conjunctivitis, but intraocular inflammatory conditions generally do not respond. Clinical experience with medrysone has also indicated that it is less likely to cause a significant rise in lOP. However, caution needs to be exercised in patients known to respond to steroids with a rise in lOP (so-called steroid responders), because pressure increases can lead to ocular damage. 

Damage to the iris sphincter muscle by high intraocular pressure, trauma, or inflammation may impair pilocarpine s ability to constrict the pupil. Clinically, these conditions can usually be excluded by a careful history taking and biomicroscopic examination. Mechanical foctors associated with malpositioned intraocular lenses or posterior synechiae may also limit movement of the iris. Depending on the extent of iris damage, the pupil may demonstrate complete to nonexistent constriction. 

There is uncertainty too as to the temptn ature of inflammation from tlic theoretical side. If it is true that tluu c is a limit of pressure and temperature defining the region of apparent ecpiilibrium (p. a 10), explosion is sim])ly the result of overstepping this limit. The laittn must then bo determined, only, if it exists, it undoubti lly dt pc nds much upon circumstances, since e.g. removal of moisi m suffices to prevent many cases of combustion (p. At... 

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