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Does anyone have any idea how to identify a substance given a random mass spec graph? There are just so many possibilities and I am stumped.

I'm not sure if this has been discussed at all on previous pages, but can anybody explain to me, or perhaps direct me in the right direction to find quality information about entomology involved in forensics as well as stages of death? Thanks.

18alia wrote:Does anyone have the density values for different NaCl solutions? The only one I could find was 10%, and according to the wiki, 25% and saturated are often available for density tests.

10% - 1.07 g/cm^3
25% - 1.19 g/cm^3
saturated - 1.25 g/cm^3

**disclaimer: only if they're made correctly**

Screw sig figs this time despite that chem cares about them

Lumitailz wrote:Does anyone have any idea how to identify a substance given a random mass spec graph? There are just so many possibilities and I am stumped.

Look for peaks at molar masses of known important components of certain components that substances can separate into when shot through the mass spectrometer (i.e. water, methane, benzene (?), etc)

19sawickin wrote:I'm not sure if this has been discussed at all on previous pages, but can anybody explain to me, or perhaps direct me in the right direction to find quality information about entomology involved in forensics as well as stages of death? Thanks.

Ento in Forensics is mainly used to determine the amount of time that has elapsed between the death of the body and when it was found, which is then calculated via knowledge of the life cycle of the insect that was found on the body. As for stages of death, AsapSCIENCE explains it pretty well here: https://www.youtube.com/watch?v=55j-nVwHa_c

Okay, sketchy stupid question here, do you know if bacterial inoculation loops can be cleaned safely with HCl to prevent sodium contamination without corroding the wire? We're probably going to use them for competition... :/

Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
raxu

daydreamer0023 wrote:Okay, sketchy stupid question here, do you know if bacterial inoculation loops can be cleaned safely with HCl to prevent sodium contamination without corroding the wire? We're probably going to use them for competition... :/

Depends on what metal it's made of. If it's made of zinc, then definitely not safe since it'll basically dissolve right away and release flammable hydrogen gas.

raxu wrote:Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
raxu

This is for animal fibers right? It turns dark brownish-blackish and shrinks

raxu wrote:Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
raxu

You can head to a hobby lobby or Michaels and tell them about science Olympiad and usually they can get you what you need from scraps laying around in about 10 minutes.

RJohnson wrote:

raxu wrote:Hello!
Our team don't have access to access to the fibers... What does "shrivels" look like?

Thanks!
raxu

You can head to a hobby lobby or Michaels and tell them about science Olympiad and usually they can get you what you need from scraps laying around in about 10 minutes.

Lol yeah that's what I did too! Another thing - if you do that, be sure they give you fabrics that are 100% of the fiber you're looking for, not a mixture of fibers (except for spandex in which you don't really have a choice)

I'm having trouble with two things.

First is solubility- sometimes I mess up and I get a soluble powder like calcium nitrate to appear as if it couldn't dissolve, at least at first. Is there a good way to ensure I got consistent results while dissolving powders quickly (since time is so important in this event)? Should I stir or no?

The other problem is that at least when I look at hairs under a microscope I can never see the shape of the hair, just a black strip, which makes them all look the same. Am I just using low quality microscopes? Should I try changing the height of the slide? Or am I just bad at seeing?

Okay, for hairs are you allowed a microscope at the competitions?

At MIT, we had to identify by feel, touch, and taste if you yolo-ed---no microscopes were provided.