Ordinate-intercept diagram

Figure 6.1 An ordinate-intercept diagram with lines indicating mixing of atmospheric Ar with nonatmospheric (mantle) Ar located off the figure to the upper right. Slope is proportional to the amount of mantle Ar (see text). The sample is a Mid-Atlantic Ridge tholeiite. Redrawn from Marty and Ozima (1986).

If a suite of samples contains the same amount of air Ar, we see from Equation (6.3) that the data will form a linear array with a negative slope on an ordinate-intercept diagram the slope will be proportional to the amount of air Ar in the samples. 

Figure 6.2 An ordinate-intercept diagram for Salt Lake Crater (Hawaii) xenoliths (cf. Figure 6.1). The negative slope of the correlation suggests that mantle Ar dominates over atmospheric Ar in these samples (see text). Reproduced from Rocholl et al. (1997).

Both kinetic parameters, the nucleation rate and the rate of crystal growth, can therefore be determined with the slope and the ordinate intercept of the straight line in the number density diagram. These quantities give according to the following equation, the median value Z5Q of the grain size distribution ... 

The dissociation constants of weak acids are determined, in the described manner, according to conductivity measurements. From the diagram of the dissociation of acetic acid it follows that the intercept on the axis of ordinates log K c = log Kc = —4.756, from which the true dissociation constant Kt = = 1.75.1(T5 at 25° C. 

This line in the double logarithmic diagram (equal abscissa and ordinate scales) shows for log [HCOf ] versus pH a slope of +1 and the line intercepts at pH = pAT) with [H2CO ]. 

The slope of each line corresponds closely to the respective seawater ratios. For calcium, a positive intercept of the regression line with the ordinate provides evidence for the presence of a nonmarine component. It should not be assumed that its contribution is constant with time, but it appears that the variation is buried in the statistical scatter of the data. It must further be emphasized that the points in a scatter diagram do not generally fall on a straight line. A linear correlation is obtained only if the contribution from one source greatly exceeds that of all others. Only then is a linear regression analysis really warranted. 

In Nyquist plots (imaginary part vs. real part of the impedance) for each separated physical process, a semicircle is obtained. Mostly, the imaginary part is plotted as an ordinate in positive direction because the inductivities do not play an important role in sohd electrolyte cells. Ideally, the middle point of the semicircle is located on the real axis. This equates an/ C combination. In reahty, due to the inhomogeneity of the electrode, depressed semicircles are obtained with middle points below the real axis. The intercepts with the real axis and maxima are related to a resistance and capacitor. The complex impedance diagram is not unambiguous. It is useful to interpret this by means of an equivalent circuit in terms of values of physical processes [6]. In Fig. 2... 

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