Directional smelling

Various specialized structures may aid in sampling air or improving directional smelling. The elephant s tnmk can be seen as an olfactory periscope tube-nosed bats Murina and Harpiocephalus spp., Vespertilionidae) and hammerhead sharks (Sphyrnidae) represent bizarre examples of specialized olfactoiy anatomy. Nostrils of lower vertebrates tend to be farther apart than those of higher vertebrates that have more flexible heads and necks (Stoddart, 1983). 

An interaction between main olfaction and the trigeminal somatosensory system has been proposed to facilitate directional smelling. For carbon dioxide and menthol, human subjects were able to tell the odor direction in 96% of cases, while the results for hydrogen sulfide and vanillin were random (Kobal et ah, 1989). Rats can discriminate odor direction in one sniff (Rajan et ah, 2006). 

Ammonia solution (concentrated). The commercial concentrated ammonia solution is a water-like liquid with a characteristic smell, owing to the evaporation of ammonia gas. It has a density of 090 gem-3, contains 58-6% (w/w) NH3 (or 0-53 g NH3 per ml), and is approximately 15 1 molar. It should be handled with care, wearing eye protection. Direct smelling of the solution should be avoided. The solution should be kept far apart from concentrated hydrochloric acid to avoid the formation of ammonium chloride fumes. 

Odors play a much greater role in human behavior than previously thought. The sense of smell provides a direct link with the function of the brain therefore, the further study of olfaction can only advance the learning of causes and effects of stimuli to the brain. 

Sulfur oxides (SO,) are compounds of sulfur and oxygen molecules. Sulfur dioxide (SO2) is the predominant form found in the lower atmosphere. It is a colorless gas that can be detected by taste and smell in the range of 1, (X)0 to 3,000 uglm. At concentrations of 10,000 uglm , it has a pungent, unpleasant odor. Sulfur dioxide dissolves readily in water present in the atmosphere to form sulfurous acid (H SOj). About 30% of the sulfur dioxide in the atmosphere is converted to sulfate aerosol (acid aerosol), which is removed through wet or dry deposition processes. Sulfur trioxide (SO3), another oxide of sulfur, is either emitted directly into the atmosphere or produced from sulfur dioxide and is readily converted to sulfuric acid (H2SO4). 

By far the most important sulfide is CS2, a colourless, volatile, flammable liquid (mp — 111.6°, bp 46.25°, flash point —30°, autoignition temperature 100°, explosion limits in air 1.25 50%). Impure samples have a fetid almost nauseating stench due to organic impurities but the purified liquid has a rather pleasant ethereal smell it is very poisonous and can have disastrous effects on the nervous system and brain. CSt was formerly manufactured by direct reaction of S vapour and coke in He or steel retorts at 750 1000°C but, since the early 1950s, the preferred synthesis has been the catalysed reaction between sulfur and natural gas ... 

H2Se (like H2O and H2S) can be made by direct combination of the elements (above 350°), but H2Te and H2P0 cannot be made in this way because of their thermal instability. H2Se is a colourless, offensive-smelling poisonous gas which can be made by hydrolysis of Al2Se3, the action of dilute mineral acids on FeSe or the surface-catalysed reaction of gaseous Se and H2 ... 

The actual mechanism or process involved in the operation of smelling is not exactly known. The most important investigation in this direction is that of Backmann. He observed that in order that a substance may be odorous it must be sufficiently soluble in both water and in the lipoid fats of the nose cells. The odours of the saturated aliphatic alcohols first increase as the molecular weight increases and then decrease. The lower alcohols are comparatively odourless because of their low degree of solubility in the lipoid fats, while on the other hand the highest members are odourless because of their insolubility in water. The intermediate alcohols which are soluble in both fats and water have powerful odours. Backmann used olive oil in his experiments as a substitute for the lipoid fats. 

The well-known phenomenon of smell-fatigue is explained by the theory that actual chemical reaction takes place between the odoriferous body and some reacting material in the nose thus it can easily be conceived that some sort of addition reaction takes place and that directly the osmoceptor in the nose becomes saturated no further reaction is possible and no further odour can be appreciated until fresh osmoceptor has been formed. Ruzicka has suggested that two such osmoceptors are involved since substances inspired in a concentrated state have odours different to those perceived in a dilute condition. He suggests that one osmoceptor reacts more readily than the other and in consequence is the more readily saturated or consumed, this osmoceptor is responsible for the sensation produced when dilute odours are inspired. If the odour be concentrated, the first osmoceptor is saturated almost instantaneously and then the sensation produced is the result of the reaction between the odoriferous substance and the second osmoceptor. 

Since traces of SO2 (which has a bad smell) may be obtained from the thionyl chloride, it is preferable to avoid this disadvantage by carrying out the esterification directly. 

Subsequently, it was shown that cyclopentadienones are very efficient in trapping 2//-azirines formed transiently during the thermolysis of vinyl azides,109 and that 3//-azepines may be formed by heating the vinyl azide directly in the presence of the cyclopentadienone rather than with the often foul-smelling 2//-azirine.31,109 An example of this procedure is the preparation of the dihydro-3/f-naphth[2,l-fe]azepine 29 by thermolysis of 4-azido-l,2-dihydronaph-thalene (28) with 2,5-dimethyl-3,4-diphenylcyclopentadienone in refluxing toluene. 

Food colorants are analyzed either by direct inspection (sensorial analyses) or by physical or physicochemical instrumental methods. Direct inspections determine the sensorial attribute of color, frequently combined with assessments of smells and flavors. Visual color assessment is subjective and may be used with reliable visual evaluations controlling multiple variables. 

Possible danger to respiratory tract from fumes ammonia, acetone, nail polish remover, heated sulfur, moth balls Make sure there is good ventilation. Never smell fumes directly. Wear a mask. Leave foul area and notify your teacher immediately. 

Some hydraulic fluids have a bland oily smell, while others have no smell. Mineral oil and polyalphaolefin hydraulic fluids are mixtures that have oil in them and will bum. Oil-in-water hydraulic fluids (a special type of mineral oil hydraulic fluid) do not bum because they contain water. Organophosphate ester hydraulic fluids are mostly made without oil and will not bum unless there is a flame directly on them once the flame is removed, these fluids will stop burning. Because they do not bum, organophosphate ester hydraulic fluids are used in airplanes and other places where fires are very undesirable. 

Some of the pyrolysis volatiles effused out, and could have been perceptible symptoms of the deterioration and an imminent disaster, but in open yards, unattended warehouses, or on trucks nobody was present to smell the odors. The cavities grew in all directions, approaching a pack surface one or two weeks after stacking. At that point air gained access to the hot charred material and triggered ignition. The combustion spread rapidly along the pack surface, possibly also into the opened cavity as air rushed in. 

It is important to notice that H2S loses its characteristic smell at about 50 ppm, and, therefore, no direct possibility for its detection exists. The density of H2S is slightly higher than that of the atmosphere (relative density 34/29). Therefore, H2S has a tendency to accumulate in, for example, pumping stations and manholes. As it is typically not detected by its smell at those concentrations, where it is life threatening, instruments or alarm systems for its monitoring must generally be used when working in sewer systems. 

The subjective experience of how strong a smell is relates to the amount of petrol in the air and the amount is directly proportional to the pressure of gaseous petrol. We call this pressure of petrol the partial pressure p(petrol)-And if several gases exist together, which is the case for petrol in air, then the total pressure equals the sum of the partial pressures according to Dalton s law ... 

Petrol containing a lot of benzene smells more strongly of benzene than petrol containing less of it. In fact, the intensity of the smell is in direct proportion to the amount of benzene in the petrol at equilibrium, the pressure of vapour above a liquid mixture... 

Adding table salt to gravy causes its lovely smell to become less intense. This is a general result in cooking adding a solute (particularly if the solute is ionic) decreases the smell, in just the same way as adding table salt decreased the smell of brandy in the example directly above. 

Thioetherification of PECH is feasibly performed in DA-solvents as already described in the patent (20J. For example, the highest substitution was obtained by the reaction of P(ECH-EO)(1 1 copolymer of epichloro-hydrin and ethylene oxide) and equimolar thiophenoxide in HMPA at 100°C for 10 h as DS 83% for sodium and 93% for potassium salts. The DS in our nucleophilic substitution was estimated by the elemental analysis as well as the titration of liberated chloride ion with mercuric nitrate (21). In the latter method, reacted medium was pretreated with hydrogen peroxide when the reductive nucleophiles which can react with mercuric ion were used. As described before for PVC, thiolation was also achieved conveniently with iso-thiuronium salt followed by alkaline hydrolysis without the direct use of ill-smelling thiolate. The thiolated PECH obtained are rubbery solids, soluble in toluene, methylene chloride, ethyl methyl ketone and DMF and insoluble in water, acetone, dioxane and methanol. 

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