TECHNICAL INFORMATION
407
Care and Handling of Volumetric Glassware
METHOD OF READING THE MENISCUS
Fig. 1 These diagrams illustrate the procedure for observing the meniscus position described in the text.
Where water or other wetting liquid is used, the method of reading advised by NIST and ASTM is illustrated in Figure 1 and described as follows: Method of Reading “In all apparatus where the volume is limited by a meniscus, the reading or setting is made on the lowest point of the meniscus. In order that the lowest point may be observed it is necessary to place a shade of some dark material immediately below the meniscus, which renders the profile of the meniscus dark and clearly visible against a light background. A convenient device for this purpose is a collar-shaped section of thick black rubber tubing, cut open at one side and of such size as to clasp the tube firmly.” “The position of this lowest point of the meniscus with reference to the graduation line is such that it is in the plane of the middle of the graduation line. This position of the meniscus is obtained by making the setting in the center of the ellipse formed by the graduation line on the front and the back of the graduated tube as observed by having the eye slightly below the plane of the graduation line. This is illustrated in Figure 1. The setting is accurate if, as the eye is raised and the ellipse narrows, the lowest point of the meniscus remains midway between the front and rear positions of the graduation line. By this method it is possible to observe the approach of the meniscus from either above or below the line to its proper setting.”
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