The first week of my internship is finished and so I’m sharing with you what I was working on and what I managed to do. I’ve been introduced to the first topic – titration. Fairly simple, isn’t it? Wrong! Titration is all about the details and making mistakes makes the results unreliable. This is why I had to approach the task with care trying not to make any.
The first thing I did was search for resources that I could use. I was shown the Vogel’s Textbook of Quantitative Inorganic Analysis which I decided to be one of my references for titration. It has really well written theory and instructions on specific titrations, as well as descriptions of apparatus. However, not very much practical guidance on the technique could be found and thus I had to search a bit further. The practical aspects of titration were brilliantly described by the Polish National Chemistry Olympiad, including detailed information on what mistakes to avoid and what to pay particular attention to.
After reading literature, I wrote a protocol that would help me organise the work in the lab. I listed all the main parts of the procedure and all the do’s and don’ts. Then I went to the lab and started filming. This bit was really challenging, as was not only about doing things right, but also filming it in such way that would show everything clearly, which I hope I managed to do. I had to do quite a few trials and get comfortable with being filmed until I had sufficient amount of material to choose from.
I then made the video, which I’m sharing with you now. This is a rough first edit and will definitely be improved. Some parts need to be re-shot. This includes: adding the opening with myself introducing the topic and changing the way of showing the apparatus from series of photos to the camera panning slowly across it, as well as showing the meniscus at the eye level. Hence, I’m hoping to get feedback from you before I come back to the lab. I’d be grateful for any comments and advice on what to improve or on any mistakes found. Please note that the audio will be recorded separately and added to the video. If you find it hard to follow what’s on the video, please find the detailed protocol below it.
Enjoy watching and please share your thoughts in the comment section!
- Introduction – PowerPoint slides
- Show equipment
- Clean equipment
- Pipette – rinse it with water and leave in vertical position to allow it to drip, dry the external walls with clean paper, if no droplets are present inside, the pipette is clean, there is small amount of water near the tip, and that can be discarded using the paper
- Burette – same procedure
- Conical flasks – rinse with distilled water several times, adding small amounts at a time, there is no need for the flasks to be dry
- Pipette the titrand – hydrochloric acid – into flask
- Rinse the pipette with acid – never from the bottle!, suck little acid into pipette, rotate in hands to make the acid flush the walls, discard into waste beaker
- Pipette right amount – first above the 10 ml level, dry external walls with clean paper, discard drop-by-drop to reach the 10 ml level (meniscus)
- Empty pipette into flask – touch the wall vertically to empty pipette, wait for 30 secs to make sure everything went into flask, do not attempt to get everything into flask (pipette is to deliver!)
- Rinse everything (the point where pipette touched flask) down the flask with water
- Add water – ca 10 ml (cylinder – no need to be accurate)
- Add indicator – 2-3 drops, the same amount for each of the 3 titrations
- Fill burette with titrant – sodium hydroxide, use funnel to pour more easily
- Rinse the burette with base – open the tap and pour three 10 ml portions of the titrant into the burette
- Close the tap, fill the burette with base over the “0” level and open the tap to adjust to “0” (take out funnel first), remove the drop from the tip
- Titration – always swirl the flask
- 1st titration – overshooting – add 1 ml at the time and check if colour changed
- 2nd and 3rd titration – the last 1 ml drop by drop (can use the first flask to compare)
- Take 2 volumes and if the difference is no more than 0.1 ml, take average
- Calculations – PowerPoint slides