exp 16 video in pre-lab

[robert zellmer]

There are some changes to the procedure shown in the video.

1)  Thermometer is incorrect. You're using a lollipop thermometer.

2)  You don't weigh out the sample as shown by weighing
     the vial before and after adding sample to the test tube.

     Instead you use a weigh boat.  You tare the balance.
     Put an empty weigh boat on the balance (they weigh
     around 3 g).  Make a mental note of the mass.  Add
     about 0.3 g of sample.  Record this mass (boat + sample).
     Add the sample to the test tube.  Go back and reweigh
     the "empty" weigh boat (after taring the balance).  Some
     sample will likely have remained behind in the weigh boat.
     You get the mass of sample actually added to the test tube
     by difference.

     While adding the sample it's easiest to put the test tube
     in the air jacket.  Remove the thermometer apparatus
     slightly, just enough to pour in your solute.  Try not to get
     the solute on the sides of the tube.  It must all be dissolved
     in the solvent before proceeding.  Do NOT put the thermometer
     apparatus on the desk or in another beaker.  Doing so could cause
     two problems: (1) you pick up something from the desk top or from
     inside the beaker and (2) you lose some of your solvent or solution
     as the apparatus rests on whatever you put it on.

Dr. Zellmer