Amos Turk

Smell of danger: an analysis of LP-gas odorization.

LP-gas derives warning properties from the odorants ethyl mercaptan or thiophane. Laboratory tests have implied that the average person has the ability to smell the odors before leaking LP-gas reaches one-fifth its lower limit of flammability. Generally, however, laboratory tests ignore or discard persons with a poor sense of smell, especially the elderly and persons with certain types of hyposmia. Some persons who apparently can smell the warning agents when directed may otherwise fail to notice or identify them. Elderly men seem particularly vulnerable to instances of incidental anosmia and olfactory agnosia. Psychophysical testing of the warning agents has been rather unsophisticated. There exists neither a standard protocol for testing nor adequate specification of the perceptual properties that might make one warning agent better than another. Without such developments, improvement in warning agents will fail to occur. Possible improvements include increases in concentration, the use of blends to insure more uniform delivery of agent and, to decrease the perceptual vulnerability of relatively insensitive people, use of agents with favorable psychophysical (stimulus-response) functions and use of agents with favorable adaptation characteristics. Even without a change in existing products, it seems advisable to learn more about the vulnerability of LP-gas users and to employ educational means to reduce risks.

Expressions of gaseous concentration and dilution ratios

Ratios of dilution or concentration of a gas sample are expressed as a pollutant quotient, or, if appropriate, an odorant quotient, Z, denoting the ratio of a pollutant (or odorant) concentration to some target concentration. The expression pZ is defined as + log10Z, so that a positive value of pZ implies dilution and a negative value concentration. The effect of particulate matter on the Z function is considered. Various examples are given, including conversions from other common dilution expressions.

ODOROUS ATMOSPHERIC GASES AND VAPORS: PROPERTIES, COLLECTION, AND ANALYSIS

Many practical odor problems, like those involving the tracing of odors to their sources and methods for odor control, must ultimately be solved by actual identification and isolation of chemical components for individual study. Much of our present information on constituents of common odors is purely nominal and based on old and incomplete research. To say, “body odor is butyric acid,” or “cigarette odor is pyridine,” is merely to use convenient abstractions for what are actually very complex and little-understood mixtures. Workers in other fields have faced parallel problems in which separation and analysis of chemical components were found to be important aids to understanding the properties of mixtures. For example, petroleum chemists have for some years appreciated the complexity of a mixture such as gasoline, and have devoted considerable efforts to its ultimate analysis and to detailed studies of the performance of its individual components.6 In this paper, the properties of atmospheric odorants and the relation of these properties to the problems of collection and analysis are critically reviewed. Methods of collection by sorption, condensation, and solution with and without chemical reaction are considered.

Rapid evaluation of oxidation catalysts supported on activated carbon

Abstract Electron spin resonance and thermal analysis have been used to investigate the catalytic oxidation of organic vapors adsorbed on activated carbon. Particular attention is given to determination of the temperature interval between oxidation of the adsorbate and burnoff of the carbon, and to the study of the oxidation states of the catalyst during repeated adsorption-oxidation cycles.

Comparative odor control performance of activated carbon and permanganated alumina

Abstract Activated carbon and permanganated alumina were compared with regard to their effectiveness in reducing the odor levels of air streams containing olefin. ester, aldehyde, ketone, amine, sulfide, mercaptan, decomposed crustacean shell vapor, or state tobacco vapor. In all cases, the odor-reducing effect of the activated carbon was much faster than that of the permanganated alumina. For the odors of stale tobacco and decomposed crustacean shells, the permanganated alumina, after it was reduced to MnO2, gave evidence of prolonged partial odor reduction, probably by serving as a catalyst for oxidation by air.

CATALYTIC OXIDATION OF ADSORBED HYDROCARBONS

There is a category of odorous emissions to the atmosphere from which the odorant components cannot be economically removed by any currently available technology. This category comprises gas streams in which the odorant is too dilute to contribute enough thermal energy for any significant temperature rise toward incineration or catalytic combustion, but not dilute enough for nonregenerative activated carbon adsorbers to be either economically attractive or amenable to solvent recovery operations, and chemically too refractory to be destroyed by ambient temperature chemical reagents such as ozone or permanganate. Despite these delimitations, such gas streams are far from uncommon. Typical components are odorous hydrocarbons such as styrene, in ranges of concentration near 100 ppm

Influence of carbon-treated air on odor perception

Abstract Air purified by activated carbon can be distinguished in odor from ambient air by some subjects but not by others. The former group perceives the odor of l-carvone in carbon-purified air to be more intense than in ambient air. The latter group perceives it to be less intense. The findings raise questions about the validity of the techniques commonly used in odor dispersion modeling and in measuring odor intensities and thresholds.

Enhanced desorption of atmospheric samples from activated carbon.

It has been previously shown that the desorption of either a chemisorbed or a physically adsorbed gas can be enhanced by the subsequent introduction of a foreign gas. Under conditions in which desorption recovery of butane from activated, carbon was 50 to 65%, subsequent adsorption of CCl4 enhanced the recovery of butane to 100%. Recovery of CCl2F2, originally 79%, was enhanced to 99% by the same method. The method of enhanced desorption was applied to the recovery of samples from activated carbons exposed to atmospheres in Chicago, New Orleans, Philadelphia, Washington, D. C, and Cincinnati. Three different types of carbons, characterized by different distributions of pore diameters, were used simultaneously in the Cincinnati sampling. In general, the enhanced desorption technique was advantageous in providing analytical information on adsorbed samples recovered from carbon media. The enhancement effect is especially marked with hydrocarbon material. The effects of these structural attributes of the carb...

Assessing the Performance of Activated Carbon in the Indoor Environment

Assessing the service life and performance of an activated carbon system requires the monitoring of carbon saturation and post-carbon air over time. For any selected environment, such performance can be predicted with the aid of an air sampler comprising 16 adsorption cartridges mounted on a manifold plate. Various methods of analysis of carbon for saturation are evaluated and compared. The partially saturated carbon can be used for sensory evaluation of the post-carbon air. The sampler can also be used for competitive tests between different kinds of adsorbents in the same environment.

EXPERIMENT 26 – Synthesis of Aspirin

You will be given approximately 3.0 g of salicylic acid. Set aside a small sample (appx. 20 mg) in a corked and labeled 13x100 mm test tube for later ferric chloride analysis and weigh the rest into a clean, dry 125 mL Erlenmeyer flask. In the fume hood, add 6.0 mL acetic anhydride via pipet. To this white slurry, add 3-4 drops concentrated sulfuric acid. Heat the flask in the hot water bath with periodic swirling for a period of about seven minutes, then allow it to cool to room temperature on the benchtop.