wec01 wrote:fastllama wrote:What is the pH of sucrose? I have 5 for my forensics notes. Why is more acidic than glucose?
For Rf, wouldn't it be different every time? Since it depends on where you stop the solvent, the denominator will change.
I believe sucrose should be close to neutral; I don't see why it would produce enough protons to make it acidic. For Rf's, the denominator does change but so will the numerator since the substances travel a distance proportional to the distance the solvent does.
Even when both change, it is near impossible to hit the same exact Rf values every time, ESPECIALLY with paper chromatography, which doesn't turn up consistent results anyways.
CPScienceDude wrote:pikachu4919 wrote:You'll get a candle. However, there's a chance it might not work, because the supervisor rarely changes out her supplies. You might get a candle with barely any wick or barely any wax or something, which is a huge rip but uncontrollable by the rest of the world.
Wow. I felt that on a spiritual level. I got a candle no wick at all at states and 2 matches. The helpers would not let me take a candle from another station, or let me have more matches. Yeah. I had to eyeball the whole hairs and fibers section (the microscope nearest to me didn't work, and the other one was being used every time I looked over. This is likely the reason I got 8th instead of 5th or up
Disclaimer: the following is a terrible way of thinking about it, and it's really unfortunate, but it will probably work out at least just for this particular situation.
As much as you want to shoot for accuracy, your actual overall goal is to just do better than the others, and whether you do that with a 90% or a 60% doesn't matter.
The way it's designed, there will be teams that will waste their time trying to do things that ultimately won't be of much help in the long run. And for some teams, they will waste their time on ID and not leave time to answer the supplemental trivia questions. If you recognize that a small particular part of the lab portion is not working out for you and eating lots of your time, then wing it and move on to something else. If you can capitalize on points in other parts of the test that can go by much more quickly, then that will give you a huge leg up on teams that hyper-focus on small portions. By no means is this an excuse to skip the ID altogether, since you'll still need it to get you closer towards a full score, but it's not the end of the world to skip portions if you can make up the lost points elsewhere.
So, between me and my partner when I was a competitor, I primarily did polymer ID, and honestly, for the reasoning above, at some point, I considered hair to be more of a throwaway ID category for me. If the microscopes weren't working out, then I considered it as a waste of my time, and I would just look at the hair, make a best guess, and then try to maximize my points across other areas such as all the trivia questions in between. Fibers are doable without a microscope, since there are often very subtle differences in the burn test in which you can tell apart the specific kinds of fibers, you just have to observe them in practice and then be able to notice them in competition as well.
wec01 wrote:blueflier2000 wrote:does anyone know what the long/short/no/both fluorescent properties mean for the TLC nats test?
Basically you'll put the TLC under a blacklight and see if it fluoresces under different wavelengths.
Yep. I think I actually skipped some parts of the TLC when I did this at nats, tbh...