How do you check and correct beaker volume marks?

I grab a graduated cylinder
https://en.wikipedia.org/wiki/Graduated_cylinder
volumetric pipette
https://en.wikipedia.org/wiki/Volumetric_pipette
or volumetric flask
https://en.wikipedia.org/wiki/Volumetric_flask
(preferably a Class B or Class A one)
place it on a level surface fill it up with water to the mark, and pour it on the beaker.

Often, beaker marks are way off.
How can you actually etch glass with the correct mark?
Right now, I only place a strip of masking tape and draw a line with a sharpie.

Comments

  • PharmaPharma Member, Pharmacist
    edited May 30
    Beakers aren't meant to be precise. Use scales and take the marks for what they are, a rough idea ;) . Etching can be done with hydrofluoric acid. Depending on where you live you may buy pens containing HF. Because it's highly toxic it's not readily available everywhere. Ask a glassblower.
  • pardon my ignorance, since i am not a chemist, have no lab training and i am just a hobby formulator wannabe  ;)

    but how do you measure liquids then, for a liquid-only formula?
    i know that in a formula with liquids and solids you measure everything by weight not volume, but what if it's all liquids?
  • PharmaPharma Member, Pharmacist
    edited May 31
    I still measure them by weight.
    If I don't have their density and had to cook according to a recipe which only gives volumes: high-grade graduated cylinders are usually fairly accurate and can be used depending on required precision, whereas volumetric flasks and pipettes as well as syringes are more precise. But because volumetric flasks/pipettes are fixed volume and a PITA to clean and not suitable for viscous or hot liquids whilst syringes are usually fairly small, I still like going by weight no matter what.
  • PerryPerry Administrator, Professional Chemist
    @bellbottom - You should do all your measurements in mass (aka weigh them on a scale). Using volume to measure liquid is not a good idea when formulating.

  • #bellbottom google specific gravity & how it effects the difference between weight (g kg) & volume (mL L). It’s easy once you know how. 
    Dr. Catherine Pratt
    (B.Sc with HONS I , Ph.D Analytical/Organic Chem and Microbiology), Cosmetic Chemistry IPCS)
  • Sorry did you already mention that..
    Dr. Catherine Pratt
    (B.Sc with HONS I , Ph.D Analytical/Organic Chem and Microbiology), Cosmetic Chemistry IPCS)
  • GuntherGunther Member
    I asked because in some formulations you need to top if off to 100%, usually to compensate for water evaporation because of heating.
    Therefore you need an accurate mark.
  • PharmaPharma Member, Pharmacist
    edited June 2
    Here's how:
    Weigh the beaker = tare weight. Add all the ingredients (without water) = total weight.
    The amount (of water) to be added = tare weight + theoretical final weight - actual weight of beaker with ingredients.
  • DoreenDoreen Member
    Sorry did you already mention that..
    Only Perry can delete a post, and I saw too late that the reply I wrote was already given, so I changed my post to 'already answered'. (as my post had become unnecessary, but unfortunately I can't delete it.)
  • Perry said:
    @bellbottom - You should do all your measurements in mass (aka weigh them on a scale). Using volume to measure liquid is not a good idea when formulating.

    Thank you!
  • #bellbottom yes that’s correct & don’t forget to use the metric scale!!

    Dr. Catherine Pratt
    (B.Sc with HONS I , Ph.D Analytical/Organic Chem and Microbiology), Cosmetic Chemistry IPCS)
  • GuntherGunther Member
    Thank you all guys.

    Will try some glass etching or sandblasting to see how it goes.
  • SchehrSchehr Member
    Just a warning, if you etch the glass on the beaker, do not use it to heat anything after, it may shatter or "explode".
Sign In or Register to comment.