Crime Busters B

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drcubbin
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Re: Crime Busters B

Post by drcubbin » March 27th, 2018, 1:12 pm

dholdgreve wrote:Not usually... Nothing says they can't, but usually it is just distilled water. FWIW, using the same ink can provide SUBSTANTIALLY differing results with the different solvents. Even if the ink is soluble with both, the color fractionalization can be totally different.
Much appreciated! :D

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Re: Crime Busters B

Post by strawberryy » April 5th, 2018, 1:36 pm

is it possible to get diff tests in the comp?

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Re: Crime Busters B

Post by strawberryy » April 5th, 2018, 1:44 pm

is it possible to get diff tests in the comp?

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Re: Crime Busters B

Post by drcubbin » April 5th, 2018, 5:17 pm

strawberryy wrote:is it possible to get diff tests in the comp?
If you mean that different teams will get different tests at the same event, I don't believe so. It enough to make up one test per event :shock:

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Re: Crime Busters B

Post by dholdgreve » April 6th, 2018, 7:31 am

strawberryy wrote:is it possible to get diff tests in the comp?
On the other hand, if your question is " Is it possible to be provided (DENSITY) DIFFERENTIAL tests in the competition?" the answer is yes. The Event Coordinator may provide various density liquids using blends of saltwater, alcohol, or cooking oil... even high fructose corn syrup... each has a different specific gravity or density that can be used to identify various polymer unknowns. Due to competition time constraints, I've always carefully massed my density liquids ahead of time, and labeled them with the specific gravity, but I heard of competitions that don't do this, and require the kids to determine the SG of each liquid so they can then test their polymers.

BTW, the density solutions containing alcohol, are difficult to control. If the lid gets left off, the alcohol can vaporize, concentrating the heavier water... so the SG may be slightly higher as the day goes on...
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Re: Crime Busters B

Post by strawberryy » April 6th, 2018, 9:28 am

dholdgreve wrote:
strawberryy wrote:is it possible to get diff tests in the comp?
On the other hand, if your question is " Is it possible to be provided (DENSITY) DIFFERENTIAL tests in the competition?" the answer is yes. The Event Coordinator may provide various density liquids using blends of saltwater, alcohol, or cooking oil... even high fructose corn syrup... each has a different specific gravity or density that can be used to identify various polymer unknowns. Due to competition time constraints, I've always carefully massed my density liquids ahead of time, and labeled them with the specific gravity, but I heard of competitions that don't do this, and require the kids to determine the SG of each liquid so they can then test their polymers.

BTW, the density solutions containing alcohol, are difficult to control. If the lid gets left off, the alcohol can vaporize, concentrating the heavier water... so the SG may be slightly higher as the day goes on...
drcubbin wrote:
strawberryy wrote:is it possible to get diff tests in the comp?
If you mean that different teams will get different tests at the same event, I don't believe so. It enough to make up one test per event :shock:


thanks!

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Re: Crime Busters B

Post by Herpgeek » April 18th, 2018, 1:27 pm

Does anyone know why solid KI would be added to the crime busters kit? Liquid can test for starch but why solid?????

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Re: Crime Busters B

Post by hippo9 » April 18th, 2018, 1:34 pm

Herpgeek wrote:Does anyone know why solid KI would be added to the crime busters kit? Liquid can test for starch but why solid?????
Isn't liquid KI just dissolved in water? I think they just want you to dissolve it yourself.
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Re: Crime Busters B

Post by Herpgeek » April 18th, 2018, 7:32 pm

Lugols solution to measure starch is KI + Elemental iodine in specific amounts, I am not sure what just adding KI to water gets you.

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Re: Crime Busters B

Post by dholdgreve » April 19th, 2018, 8:55 am

Herpgeek wrote:Does anyone know why solid KI would be added to the crime busters kit? Liquid can test for starch but why solid?????
"Solid KI" is not on the official list of items allowed in the kit from National Rules, and liquid potassium Iodide is to be provided by the event coordinator, not brought with you in the kit. I have never heard of solid potassium iodide, but I have seen and used iodine crystals, in making my own lugol's solution. You cannot just dissolve iodine crystals in water to get the starch indicator... you must first dissolve potassium chloride in water, then add the iodine to make is soluble.
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