Transmission spectra mixture

After cooling the electrodes and inletting an air in the bell jar, a soot is removed from the chamber walls, weighed on an analytic balance and filled with toluene. After storing the soot in toluene for several days, we measured the transmission spectrum of the mixture with a SF-26 spectrophotometer. Then the colored mixture is poured out, the residual toluene is evaporated at the temperature T = 500 K from the soot and it is weighed once again. The relative content of fullerens in the soot is measured from these data [2,3]. 

Spectra collected by these fom methods of an oxidized layer on 50-70-p,m galena particles (natural PbS, n 4) using the same number of scans (100) and resolution (4 cm ) and a Perkin-Ehner 1760X FTIR spectrometer equipped with a mercury-cadmium-teUmium detector are shown in Fig. 2.51. Because of strong backscattering by the PbS particles and, as a result, a small penetration depth of radiation, the transmission spectrum obtained from the powder squeezed between two plane-parallel KBr plates represents mainly the component /q that has passed by the particles (Fig. 1.22) and, hence, bears no information on the sample absorption. The DRIFTS and DTIFTS spectra of the PbS powder and the transmission spectrum of a mixture of PbS and KBr spectra are more informative. The distinct absorption bands of surface oxidation products at 1440, 1400, and 1200-1100 cm are assigned to lead carbonate, hydroxide, and sulfoxide [109],... 

Fig. 2. Comparison of reflection spectrum (a) and transmission spectrum (b) of partially decationized zeolite NaX in a 1 1 mixture with Aerosil, recorded on a dispersive spectrometer. Reproduced with permission from Izv. Akad. Nauk, Ser, Khim, 40 (1984).

Figure 21. IR transmission spectrum of DICH (a), AP2PFIO4 POSS (b) and a mixture of DICH and AP2PFIO4 POSS (c) deposited on an A1 substrate.

A mixture consisting of aniline ( 0.2 g) and (lS)-(+) camphorsulfonic acid (3.48 g) was dissolved in 10 ml of water and then treated with five separate portions of 0.1 g of ammonium peroxydisulfate dissolved in 1 ml water. Each successive portion was added when the solution turned from blue to green while the reaction mixture was maintained at 20°C. After the additions were completed the mixture was centrifuged and the product washed with water. The circular dichroism spectrum of the product suspensed in water indicated a molar ellipticity of about 90 x 103 deg-cm2/dmol. Transmission electron micrographs showed that the product had a nanofibrous structure with fiber diameters from 30 to 70 nm and had a length of several hundred nanometers. 

IR spectra were collected during the entire course of reaction by a Nicolet MAGNA 550 Series II transmission infrared spectrometer. The background spectrum was taken upon injection of the reactant mixture. The background spectrum was subtracted from the spectra collected during in situ study to obtain the absorbance of the species in the reactor. The MFC yield is defined as the molar ratio of carbamate produced to aniline consumed. The DMC and DMPD yields were calculated by the same procediure with moles of methanol consumed and moles of DMC consumed, respectively. 

Similar considerations are important in Py-MS cold spots and wall contact in the Py-MS vacuum systems can also affect transmission of pyrolysates." Py-MS produces a pyrogram of all compounds in the pyrolysis product mixture superimposed in a single mass spectrum. For that reason, interpretation of Py-MS results from a complex sample can be more difficult than interpretation of a Py-GC/MS pyrogram, in which pyrolysis products are chromatographically separated before MS detection. As pointed out by Snyder et al., Py-MS with relatively cold pyrolysis interface walls or with expansion chambers tends to provide only low mass range analysis (under m/z = 2(X)). When direct Py-MS is performed with the pyrolysis reactor close to the ion source, so as to detect larger mass pyrolysis products (m/z = 200 to 1000), the ion source tends to contaminate rather quickly, jeopardizing reproducibility. 

Often the combination of spectral and temporal resolution is helpfiil to simultaneously determine the individual concentrations of the different components in a mixture of pollutants, even if their absorption spectra overlap. An example is the pollution of water by different types of oil. In Fig. 10.25a the transmission curves of three different oil sorts (Diesel oil, gasoline and heavy oil) are shown and in Fig. 10.25b their emission spectra, while Fig. 10.25c shows the decay curves of the different sorts. Such measurements can help to find the polluter. In Fig. 10.26 the total fluorescence spectrum of a mixture of different aromatic hydrocarbons is shown together with the contributions of the different components, obtained by the different detection techniques discussed above [1481]. 

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