Lab Manual Update

Oct 7, Tuesday, I spent another 3 hours on Lab 19. revisions:

I tried to replicate what I did the day before but cut the volumes in half.  

Using the same samples as above, I kept adding DI H2O to sample #4 to bring down the absorbance. I was able to bring down the absorbancec to 1 for #4 by adding a total of 5 mL of DI H2O.  After recalibrating it though, it went up to 1.2-1.3 agaqin.  Go figure!  The only saving grace is I still got a good linear correlation.

Then I tried just adding 1 mL of DNSA instead of 2 mL of DNSA.  Not as good correlation and the absorbance for #4 is still higher.

I think I will stick with 1/2 the volumes of H2O and 0.2% glucose and DNSA as the paper and then add 5 mL of H2O after heating.  This seems to be the best combination.  It also might help to run the samples right away.

Next, I worked on revising Lab 3102 for Chem 31.  I am using parts of the household chemicals lab published in J. Chem. Ed 2001.  I am adding MgSO4, cornstarch, CaSO4 and removing Na2CO3.  I tried all the reactions with the knowns using vinegar, KI/I2, NaOH and tested the solubility in water.  I started testing the procedure for the unknowns but have not finished it.

Next time I am on campus, I want to try:

Lab 19.2:  Half the volumes of H2O, 0.2%, and DNSA plus 5 mL of DI after heating.

Lab 3102:  Try different combinations of unknowns (one soluble, one insoluble in water)