How do you read a stalagmometer?

Answer 1

Use of the Stalagmometer allows for easy measurement of surface tension in solutions. The specified stalagmometer, 2.5 mL volumetric, is used to calculate the surface tension by measuring drop weight per volume of a sample in relation to a reference liquid. As a liquids drop weight is relatively proportional to its surface tension, the surface tension of a sample can be determined by comparison of the drop weight to that of a known reference liquid. This provides the formula: Surface Tension Measurement: 1. Remove a sample of solution from the bath and allow cooling to room temperature. 2. Position the stalagmometer on a pipette stand so that the sample solution can drip from the flat end of the instrument. 3. Using a pipette bulb, draw the cooled solution up past the top graduation mark on the stalagmometer. 4. Remove the pipette bulb and watch the bubble edge of the solution as it falls through the stalagmometer. 5. Begin counting the number of drops that fall from the end of the stalagmometer as soon as the edge of the bubble reaches the Start Mark on the stalagmometer. 6. Continue counting the drops until the bubble edge of the sample reaches the End Mark. Record the number of drops and repeat two more times. Average the three readings and record this as "N" 7. Calculate the surface tension as follows: Surface Tension = (14401) (D) (N) D = Density of Sample Solution (If unknown, use 1.25) N = Number of Sample Drops

Answer 2

To read a stalagmometer, you look at the liquid level where it meets the graduated scale on the device. The liquid will form a concave meniscus, and you take the measurement at the bottom of this meniscus. The reading indicates the surface tension of the liquid in dynes per centimeter.