1 / 9

Physical Pharmacy SURFACE TENSION

Physical Pharmacy SURFACE TENSION. By Abdul- Wahhab Khedr Demonstrator of Pharmaceutics and Industrial Pharmacy. Surface tension of liquids. Why the free drops of water form spherical droplets?. Surface Tension:.

charleen-nigel
Télécharger la présentation

Physical Pharmacy SURFACE TENSION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physical PharmacySURFACE TENSION By Abdul-WahhabKhedr Demonstrator of Pharmaceutics and Industrial Pharmacy

  2. Surface tension of liquids • Why the free drops of water form spherical droplets?

  3. Surface Tension: • Equals the work (W) or energy necessary to increase the surface area (A) by 1 cm2 • Units: • Is defined as “ The force in (dynes) acting along the surface of a liquid at right angle to any line 1 cm in length”.

  4. Experimental Determination of Surface Tension • Drop weight and Drop number method: (Using Stalagmometer) • In this method the surface tension of a liquid (γ1) can be determined in relation to another liquid of known surface tension (γ2). a b

  5. Experiment • By using Stalagmometer, determine the relative surface tension of the given liquids with reference to distilled water (S.T=72.8 dyne/cm at 20⁰C) • Procedure: • Wash the stalagmometer several times with water before use. • Introduce the flat tip into small beaker half-filled with water, suck water till its level becomes above the upper mark (avoid entrance of air bubbles). • Adjust the level of water to the upper mark and remove any suspended drop. • Count the number of drops falling until the level of water reaches the lower mark (n1). • Repeat the procedure twice again and determine (n2) & (n3). • Repeat the procedure for the liquid to be measured after washing the apparatus.

  6. Results

  7. Comment • The drop of a mass (m) gets released when its weight G=mg is equal or greater than the surface force at the end of tube

  8. Comment • There are two line marks on the stalagmometer: top line above the wide part and bottom line bellow it. The volume between these two lines is (V), and liquid with density (ρ) contained in this volume has a mass (M) • Such a volume V corresponds to n drops, which are released from the stalgmometer upon the decrease of liquid level from top to bottom line mark. • Here, the average mass (m) of one drop is

More Related