Volumetric lamps

Further development of the emission models was made by Irazoqui et al. who introduced the three-dimensional nature of the extended light source [117]. Hence, the most significant feature of the extense source with volumetric emission (ESVE) model is the inclusion of a radiant energy source with finite spatial dimensions. In fact, the lamp is considered to be a perfect cylinder, the boundaries of which are represented by a mathematical surface of zero thickness (Figure 30). 

The main difference between photochemical and thermal reaction is the presence of a radiation-activated step. The rate of reaction of this step is proportional to the local volumetric rate of energy absorption (LVREA). For any emission model, the LVREA is a function of the spatial variables, of the physical properties and geometrical characteristics of the lamp-reactor system, and some physicochemical properties of the reacting mixture. The most important design parameter that is pertinent in photochemical and photocatalytic reactions is the effective attenuation coefficient. 

Figure 15 (a) Emission model for the volumetric lamp, (b) Limits of integration for the... 

Sulfur. The analytical methods used for determination of sulfur in petroleum oils involve combustion under oxygen pressure in a bomb, or burning the oil in a wick lamp and absorbing the sulfur oxides in hydrogen peroxide. Conventional gravimetric or volumetric methods are then employed to determine the sulfate. A turbidimetric method is recommended in the case of low sulfur contents. 

A stock solntion (1.0 x 10 " moldm ) of NaCl was prepared. Standards were made by adding 2.0, 3.0, 4.0, 6.0 or 10.0 cm of the stock solution to a 100 cm volumetric flask 5cm of MeCN were added to each flask which was then filled to the 100 cm mark with deionized water. A blank was also prepared. The sample for analysis was prepared by dissolving 8.90 mg of [X][PF6l2 xNalPFgl in 2.5 cm of MeCN in a 50 cm volumetric flask. This was filled to the mark with deionized water. This solution was diluted 10-fold with a 5% (by volume) MeCN/water solution. Using a sodinm hollow cathode lamp (A = 589nm), AAS was nsed to determine the absorbance of each standard. Each absorbance reading was corrected for the absorbance of the blank and the data are tabulated below ... 

Pipette 25.0 cm of the Mnl2 solution into suitable containers eg two to four petri dishes (9 cm diameter) and place in reproducible positions under a low pressure mercury lamp. Irradiate for a period (say 30-60 minutes) and collect the solutions quantitatively in a 250 cm volumetric flask. Titrate an aliquot against standardised Na2S203 solution using starch indicator (Sec. 11.4.4). 

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