Volatile chemical

Monkiedje et al. [10] investigated the fate of niclosamide in aquatic system both under laboratory and field conditions. The octanol/watcr partition coefficient (Kaw) of niclosamide was 5.880 x 10 4. Adsorption isotherm studies indicated that the Freundlich parameters (K, n) for niclosamide were 0.02 and 4.93, respectively, for powder activated carbon (PAC), and 9.85 x 10 5 and 2.81, respectively, for silt loam soil. The adsorption coefficient (Aoc) for the drug was 0.02 for PAC, and 4.34 x 10-3 for the same soil. Hydrolysis of niclosamide occurred in distilled water buffer at pH above 7. No photolysis of the drug was observed in water after exposure to long-wave UV light for 4 h. Similarly, neither chemically volatilized from water following 5 h of sample aeration. Under field conditions, niclosamide persisted in ponds for over 14 days. The half-life of niclosamide was 3.40 days. 

Mclachlan, M., Mackay, D., Jones, P.H. (1990) A conceptual model of organic chemical volatilization at waterfalls. Environ. Sci. Technol. 24, 252-257. 

The rate of volatilization will also increase with an increase in temperature, ten Hulscher et al. (1992) studied the temperature dependence of Henry s law constants for three chlorobenzenes, three chlorinated biphenyls, and six polynuclear aromatic hydrocarbons. They observed that within the temperature range of 10 to 55 °C, Henry s law corrstant doubled for every 10 °C increase in temperature. This temperature relationship should be corrsidered when assessing the role of chemical volatilization from large surface water bodies whose temperatines are generally higher than those typically observed in groimdwater. 

If a chemical is placed in an empty vessel that is greater in volume than the chemical itself, a portion of the chemical volatilizes to fill the remaining free space of the vessel with vapors. The pressure in the vessel at eqnilibrium is affected only by the temperature and is independent of the vessel volnme. The pressure that develops, called vapor pressure, characterizes any chemical in the liquid or solid state. 

Chemical—Volatilization, neutralization, precipitation, flocculation, adsorption, desorption, dissolution, oxidation. 

Sample introduction using GC solves many problems related to the analysis of chemicals related to the CWC. The amount of chemicals needed is low, which almost removes the danger in handling these chemicals. A drawback in the GC is that it can only be used to analyze volatile chemicals. Volatile derivatives can be made of most of the nonvolatile scheduled chemicals. 

Mackay D, Shiu WY, Ma KC (1992) Illustrated handbook of physical-chemical properties and environmental fate for organic chemicals, volatile organic chemicals, vol 3. Lewis, Chelsea, MI, pp 916... 

Environmental conditions - climatological factors, such as temperature and humidity, may influence chemical volatility, perspiration rate and use of protective clothing. Wind can have a profound effect on spray drift, and resultant exposure to the applicator. 

Merinis and Boussieres [2,3] pioneered the method of thermochromatography (TC) in application to radiochemistry. With the equipment schematically pictured in Fig. 1.1, they investigated thermochromatographic behavior of some 20 elements, mostly in the form of chlorides. The elements were some alkaline, alkaline earth, rare earth, transition, noble, and actinoid (Th and Pa) metals. The authors experimental technique was based on slow batch chemical volatilization. They obtained data on the shift in position of TC peaks as a function of the experiment duration. 

Table 3.4 Chemical Volatilization of Elements and their Deposition on Silica Tube or Chemical Filters...

The dissociative adsorption - associative desorption type of reaction also takes place when Ln or An trichlorides are chemically volatilized into the carrier gas containing a rather large concentration of A12C16 vapors. Chromatography evidently proceeds due to the equilibria like ... 

Feeding the necessary gaseous reagents into the target chamber or next to its exit to realize in situ chemical volatilization ... 

Chemical volatilization is the production of volatile compounds or the elemental state of the radionuclides by treating the original recoil atoms or other samples with appropriate, mostly gaseous, reagents, usually at elevated temperatures. 

Firstly, an analyte can be released from a solution residue and thus be brought into an atom reservoir, a radiation or an ion source free of solvent. This is particularly useful for the case of sources operated at low power and gas consumption, which are cheap but generally do not tolerate the sudden introduction of moisture. On the other hand, independence of the physical and chemical properties of the sample solvent can be gained, which may introduce physical (nebu-lization effects), chemical (volatilization effects) or spectral interferences (e.g. those stemming from band spectra of the solvent molecules or their dissociation products). 

Several questions should be answered prior to any experiment designed to measure respiratory exposure. Does the application method provide droplet sizes that are breathable Is the chemical volatile under the conditions of use Are respiratory data required at all for registration ... 

Plasma Etching, Fig. 2 Four types of reaction mechanism during plasma etching (a) sputter etching, a purely physical process (b) chemical etching, or chemical volatilization, a purely chemical process (c) ion-enhanced energetic, i.e., ion-enhanced chemical, etching, a combination of physical and chemical processes and (d) ion-... 

The rate at which a chemical volatilizes from soil is influenced by many factors, including soil properties, chemical properties and environmental conditions. 

The selection of the most appropriate model will be dictated by the nature of the chemical and the particular set of the conditions. The models presented here are distinguished in two categories (a) those applied to chemicals that are incorporated and distributed into soil and (b) those applied to chemicals volatilized from the soil surface, i.e. chemicals not incorporated into soil. 

Chemical % Volatilized after 1 day, experimental % Volatilized after 5 days, experimental % Volatilized after 1 day, calculated % Volatilized after 5 days, calculated ... 

---