A Chart with an Additional Axis

The third data series in C20 D30 produces the tick marks. (To understand how these tick marks are created, remember that when Excel creates a line in an XY chart it simply connects numerical x,y coordinates with straight lines.) Since the maximum value in the Y-axis was 12, pairs of values were entered in column D (12 and 11.8, the latter having been found by trial and error to give a tick mark of suitable length). The empty rows between pairs are necessary, otherwise the tick marks would be connected to each other by a line, making a sawtooth pattern. 

The tick marks were added to the chart by copying the table of tick mark values (C20 D30), then using Paste Special to add the new series (Series 3), then formatting the series to remove the marker points and change the color of the line to black. 

When this approach is applied to Series 3 to provide Tick Mark Labels, you ll get two superimposed data labels at each x value (for example, 12 and 11.8 if you chose to display values.) This means that you ll have to select one of the two labels and delete it, then select the other label and edit it. A better way to add the data labels is to add a fourth data series with a single point for each tick mark in this example, select C20 D20,C23 D23,C26 D26,C29 D29 and Copy, add this as a new series. Series 4, using Paste Special, then format the series to set both Line and Marker to None. Then add data labels, either values (Y values) or labels (X values), to this series. Change the Alignment of the data labels to Above. Edit the data labels individually, replacing them with the desired text. 

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Figure 5-21. Worksheet layout to produce a chart with an additional axis.

Rassivation rpm. According to the first definition of passivation, a metal is passive when it behaves like a noble metal. In these iron EDTA solutions, a noble metal such as Rt measures the Fe +/Fe + ratio of the solution. From experience, the emf measured (Rt vs. SCE) in solutions containing predominantly Fe(lll)EDTA will be more positive than -100 mV. The active steel usually exhibits an OCR (Fe vs. SCE) value of approximately -800 mV. When the steel passivates, the OCR will increase by several hundred millivolts and will eventually reach . 100 mV. To conduct the experiment, the polished active RDE was lowered into the heated prepared Fe(lll)EDTA solution. Beginning from 0 rpm, the rotation rate was slowly increased until the steel emf sudden ly rose to approximately - 300 mV. The emf and rpm were recorded on the two-pen recorder. The passivation rpm was determined from the chart recorder traces. A typical trace is shown in Figure 5. The x axis reflects chart movement or time to passivation, but the time factor was not studied. The tests were repeated three to five times, and the rpm (pass) was averaged. A number of graphical relationships between [Fe +] rpm, free EDTA, and temperature were derived from these data. In addition, with the use of the values of D calculated above and Equation (2), /um at passivation was calculated. 

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