Polarimetric estimation

Autoxidation of deoxyhumulones (24) occurs in the ring to give ( )-humulones (1) or in the side chains to give products such as (36) and (37). The a-acids if not removed from the mixture, by, for example, precipitation as their lead salts, will be oxidized further. Racemic ( )-a-acids will be included in conductometric but not in polarimetric estimations of a-acids. 

The third method is of limited application and is used only in special cases, The second is the most accurate and rapid method, and is of considerable technical importance. The chemical method (described below), although less accurate than the polarimetric method, is of great value for the estimation of sugars in biological fluids. In fact, for such purposes, it is often to be preferred to the polarimetric method owing to the probable presence of other substances having high optical rotations. 

The object of this determination, which is carried out principally with sweet wines, is to estimate the reducing sugars and any saccharose which may have been added to the wine. Both the optical and chemical methods are used (see also Sugars, General Methods). The polarimetric method is also sometimes used with sweet wines in order to ascertain if dextrin or commercial glucose has been added see later, p. 196). 

The aqueous solution is opalescent.—Aqueous solutions of glycogen show a variable but pronounced bluish-white opalescence this opalescence may be so great that 1 % solutions are unsuitable for polarimetric observations. Quantitative measurements of the turbidity of glycogen solutions have been used for estimation of the glycogen content of a solution (see pp. 268-9), and for determination of the molecular weight (see Section II). 

N4. Nebbia, G., Polarimetric method for estimating ascorbic add. Acta Vttaminol. 12, 107-109 (1958). 

The problem of particle shape is much more complex. Undoubtedly, the assumption of spherical particles is a great idealization, but so is the assumption of any specific shape. Actually, aerosols can be represented by ensembles of randomly oriented particles of different shape. Moreover, all available polarimetric and photometric observational data do not allow us to make an tmambiguous conclusion about the particle shape. Therefore, it is important to estimate the influence of the assrrmption about particle shape on... 

Despite difficulties and ambiguous solutions, the spectropolarimetric method is the only way of determining the spectral values of the real part of the refractive index. In addition, the particle size distribution and the optical thickness of the gas layer overlying the cloud layer are estimated more accurately. Furthermore, it is reasonable to expect that polarimetric methods will be more successful in the study of the physical characteristics of surface layers for atmosphereless celestial bodies. For this purpose it is necessary to obtain high-precision polarization measurements with an error smaller than 0.05%. 

Polarimetric measurements were carried out on a polarimeter with very large half-shadow angle (5°) that could not give sufficient accuracy in the estimation of the optical rotation of products. 

The data represented here should be viewed as a conservative estimate of the sensitivity of the INTEGRAL Imager. Methods of preferential event selection, with the aim of increasing the polarimetric modulation factor are currently under investigation. It is believed that with these analysis methods the sensitivity can be improved by at least a factor of two. 

Equilibration experiments have been carried out to assess the degree of chiral recognition exhibited by (iJ/J)-(28) and (/ /2)-(29) towards racemic amino acid ester salts and other substituted ammonium salts [4,30,51,52], The optically pure hosts dissolved in CHCI3 were equilibrated with HjO solutions of the racemic salts at 0°C and the amounts of each enantiomer extracted into the CHCI3 layers were estimated polarimetrically after isolation. An Enantiomeric Distribution Constant (EDC), defined as the ratio, where and are, respectively, the distribution... 

Estimated based on GPC curves obtained by UV and polarimetric detections (see text). 

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