Take-off ratio

In the preparation of a concentrate of heavy isotope as the bottom product the minimum reflux ratio (179) is replaced by the maximum bottom take-off ratio ... 

With an amount of take-off calculated according to eq. (180) an infinite number of stages would be necessary. The number of stages required with a finite reflux or take-off ratio may be calculated in the manner described below. 

The number of stages % necessary at a given take-off ratio rjZ is given by... 

Fig. 154 shows the number of theoretical stages as a function of the take-off ratio in the preparation of the stable isotope 0. The three curves represent the following oases (all figures are mole fractions) ... 

Relation between the required number of theoretical stages / and the take-off ratio r/Z (Kuhn)... 

The realization of these take-off ratios gives rise to some practical difficulty on a laboratory scale. Using Kuhn s apparatus [59] (Fig. 157) as a guide, we shall now... 

Alcoholysis of a-monoalkylacetoacetic esters may be accomplished in excellent yields by heating with catalytic amounts of alkoxide in excess abs. ethanol. The startg. m. must be dry and free of acetoacetic ester.— E Ethyl a-allylaceto-acetate added to a soln. of some Na in 2.5 moles of abs. ethanol, refluxed under a column packed with glass helices and fitted with an automatic liquid-divider head, distillation started when the temp, at the head has dropped from 78 to 72 , the b. p. of ethanol-ethyl acetate azeotrope, the take off ratio adjusted to maintain the vapor temp, at 72-73 , and excess ethanol removed on a water bath when after 22 hrs. the calculated amount of azeotrope has been collected ethyl 4-pentenoate. Y 88%. F. e. s. J. J. Ritter and T. J. Kaniecki, J. Org. Chem. 27, 622 (1962). 

Figure 3.13b shows the Si4+/Si intensity ratio as a function of take-off angle, along with a fit based on Expression (3-10). The agreement up to take-off angles of... 

The tendencies seen are quite general. For small off-axis angles, i.e. nearly perpendicular to the macroscopic surface plane, shading is relatively unimportant and the main deviating effect is due to the variation of the local take-off angle over the surface, with the result that the /(//s ratio is larger than for a flat layer... 

Figure 3.15 O Is / Ag 3d5/2 XPS intensity ratio as a function of take-off angle for two oxygen species on polycrystalline silver. The data corresponding to an O 1 s binding energy of 528.4 eV are attributed to subsurface oxygen in Ag, the other with a binding energy of 530.5 eV to oxygen atoms adsorbed on the Ag surface (data from Baschenko et al. (39J).

Figure 5. Concentration ratio of Cs to Si in obsidian as a function of analytical XPS take-off angles.

Fig. 40 Gold-to-carbon ratio as a function of the XPS take-off angle measured on gold nanoparticle assemblies on PAAm for nanoparticles having a diameter of 3.5 nm (a) and 16 nm (b). The dry thickness of bare PAAm is given in the legend. The lines are meant to guide the eye. (Reproduced with permission from [140])...

The flask is connected to a 2 by 50 cm. Vigreux column equipped with a total-reflux partial take-off head, and all but about 400 ml. of the ethanol is removed at 200 mm. pressure with a reflux ratio greater than 5 1 (Note 4). 

A further dimension may be added by carrying out angular dependent studies. For a homogeneous material, although as we have previously noted toe absolute intensity of a given core level will depend on take off angle because of instrumentally dependent factors, if we look at ratios of intensities for core levels of the same sym-... 

Fig. 35. Plot of intensity ratios of components of CXi levels and of the total F ls to Cls levels as a function of take off angle for untreated and Argon glow discharge treated samples of an ethylene-tetrafluoroethylene copolymer...

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