Fall 2007 Student Comments:

Experiment #3: Solubility and Recrystallization

do a significant amount of research on the solubility of the compounds before coming to class.  Having specific predictions will make it much easier to get a high yeild of your product.  Anytime you are washing with a solvent make sure it is very very cold so that you don't accidentally filter out your product. SP

You need patience for the recrystallization portion of this lab. The instructions say that after heating you must allow the solution to cool to room temperature and then place it in an ice bath. At first, you may have the inclination to place the hot beaker directly into the ice bath to help save time. If you do this, you definitely run the risk of having your beaker crack and having to do the experiment all over again. PH

when doing this experiment when you get to the part in which you need to place your product into the ice bath to form crystals a technique you can use to help speed up the rate at which the crystals are being formed at is by getting a stirring rod and scraping the bottom of your beaker in which the solution is in. PL

This experiment takes a long time to complete. Make sure you have a good group of people to work with as a team. This will cut down on your work load -as long as you all can communicate well with each other. EC

For this lab experiment,be careful when recrystalizing your solid. Adding too much solvent may decrease your percent yield. VG

If you wear gloves in lab ( or even if you don't!) be careful handling glassware. If your hands get wet for any reason, the gloves become extra slippery and you run the risk of dropping or knocking something over. Since so much glassware is used in organic lab, this can be an issue! BH

When vacuum filtering, make sure that your piece of filter paper fit the funnel properly; no creases, its big enough and flat. I did not ensure its position and paid the price. I started putting the paper down first then turning the vacuum on a few times to make sure it gripped it and sort of locked it into a good location to properly filter your product. CR

When using vacuum filtration to filter out your solid, it's a good idea to drizzle a little distilled water onto your filter paper after you have turned the vacuum on.  This will ensure that the filter paper sticks in place and allows for the best possible separation. AK

Make sure to record the appearance of all the standards and of your products to use later in determining your products. Don’t forget to record the temperatures of you ice bath! YM

When making your observations about solubility, it is best to ask a second opinion if you are not sure whether it is slightly soluble or soluble, because sometimes it was hard to tell the difference. This determination can make a difference in determining the correct identity of the unknown. MFL

Hexane boils away quite readily in the boiling water bath. Why not try a higher boiling point hydrocarbon solvent such as heptane (bp 98 degrees C) or octane (bp 125 degrees C)? (jbf)

Having agreed upon definitions or examples of what "somewhat soluble, soluble, very soluble..." are would be incredibly helpful.  The explanations in the lab do not necessarily provide a good description since different solution solubilities could be interpreted in different ways.  One person's soluble is another person's very soluble.  Actual examples (pre-made solutions in tubes) to look at before beginning might be beneficial. KS