Fiducial mark

Figure 8.31. Fiber scattering of PEE 1000/43 (a) at an elongation = 0.88 (b) during relaxation from = 0.88. The fiber direction is indicated by a double-arrow. Visualized region —0.15nm 1 < s 2, sj < 0.15nm 1. = (l l,) /Iq, with Iq and / defined by the initial and the actual distance between two fiducial marks on the sample...

Figure 14.1 Simplified vacuum adsorption apparatus. Shaded areas represent mercury heavy horizontal lines are fiducial marks.

The sample cell is not completely filled by the adsorbent it contains a void volume which is the volume not occupied by adsorbent, up to stopcock 4. If the calibrated volumes and manifold are filled with nitrogen at pressure Pj and stopcock 4 is opened the pressure will fall because of expansion and adsorption of nitrogen in the evacuated cell. After equilibrium is attained and the mercury in the manometer is returned to the fiducial mark the new pressure P is noted. The number of moles adsorbed is given by... 

Apparatus for measuring the speed of sound in a gas. The Kundt s tube should be a glass tube 150 cm long and 5 cm in diameter. The close-fitting Teflon piston should move over a range of at least 100 cm. If a constant-temperature jacket is provided for the Kundt s tube, the position of the piston can be determined from the position of a fiducial mark on the rod. 

The gas burette shown in Fig. 3 is constructed from two 50-mL bulbs, large-bore capillary tubing, and a stopcock (F). Fiducial marks are engraved above the top bulb, between the bulbs, and below the bottom bulb. Before the burette is attached to the vacuum system. 

The viscosimeter should be mounted vertically in a constant-temperature bath so that both fiducial marks are visible and below the water level. If a glass-walled thermostat bath that will allow readings to be made with the viscosimeter in place is not available, fill a large beaker or battery jar with water from the bath and set it on a dry towel for thermal insulation. The temperature should be maintained within 0.1°C of 25°C during a run. This will require periodic small additions of hot water. 

By suction with a pipette bulb through a rubber tube, draw the solution up to a point well above the upper fiducial mark. Release the suction and measure the flow time between the upper and lower marks with a stopwatch or timer. Obtain two or more additional runs with the same filling of the viscosimeter. Three runs agreeing within about 1 percent should suffice. 

It is important to know the densities of all solutions. A satisfactory procedure is to weigh the Gouy tube empty and then filled with water to a fiducial mark near the top. From... 

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