Reference method for measuring the surface tension of chromium electroplating: chapter 7

7. Measuring the Density of the Chromium Electroplating, Chromium Anodizing or Reverse Etching Solutions

The density of the chromium electroplating, chromium anodizing or reverse etching solution may be determined by one of two methods: 1) Direct measurement of the mass of a specific volume of solution; or 2) using a hydrometer (Baume stick). The density measurement is to be made at 25°C.

• 7.1 Direct measurement
  • 7.1.1 Equipment required:
    • 7.1.1.1 Top-loading balance which is accurate to ± 0.1 gram;
    • 7.1.1.2 10 mL or 100 mL class A volumetric flask or class A graduated cylinder;
    • 7.1.1.3 Pipette
  • 7.1.2 Procedure:
    • 7.1.2.1 Tare a clean and dry 10 mL (or 100 mL) flask on the top-loading balance.
    • 7.1.2.2 Pipette the solution into the flask such that the bottom of the meniscus is touching the fill line.
    • 7.1.2.3 Record the weight of liquid in grams.
    • 7.1.2.4 Divide the weight of liquid by 10 (or 100 if using a 100 mL flask) to give the solution density in ml.
• 7.2 Hydrometer
  • 7.2.1 Equipment Required:
    • 7.2.1.1 Hydrometer: Rated to read either a density from 1.00 to 1.30 (or greater) g/mL or a Baume reading of 0 to 35. (Note: The hydrometer must be able to measure for a density greater than the density of water.)
    • 7.2.1.2 Container: A container that is tall and wide enough to accept the hydrometer and be such that a reading can be taken from a near horizontal line. (Note: The container must be sufficiently wide to allow the hydrometer to float and not be subject to wall effects or interference from the container wall).
  • 7.2.2 Procedure:
    • 7.2.2.1 Pour the solution into the container, such that it will not overflow from the container when the hydrometer is immersed in the solution.
    • 7.2.2.2 When the solution has cooled to 25°C, place the hydrometer in the solution and allow the hydrometer to level off or stabilize.
    • 7.2.2.3 Take the density reading at the line on the hydrometer which is level with the solution.
    • 7.2.2.4 The hydrometer reading is a direct reading of the density of the solution and no calculations are required if measured in g/mL. If using Baume density, the equation for determining specific gravity in g/mL is 145 / (145 - Baume reading). The table in Appendix A may also be used to cross-reference the number of drops with the Baume reading to find the surface tension in dynes/cm.