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 91 
 on: January 08, 2019, 04:57:50 PM 
Started by pcm81 - Last post by pcm81
I just bought on ebay a used VWR 375 Hot Plate. It came in pretty crappy shape and since this is a 2nd improperly advertised item i got from this seller the seller is going to get negative review, but i do not want to waste any more $$ to ship it back so i am trying to fix it.

The heating element woks and the stirrer magnets are spinning. I took it apart and can see the magnets spin as i change the speed.

The problem that i have is that my stir bar does not spin in a good steady pattern. It does on my cheap and crappy plate, but not this one.

My question is this: Is it common for magnets in hot plates to loose their strength? I am almost tempted to just replace the 2 rare earth magnets on this stir plate with 2 new samarium-cobalt magnets,but first wanted to ask the forum members if it is a common problem to have magnetic stirrers demagnetize? The stir bar dances in the glass instead of spinning, almost as if the magnetic field from the stirrer cant manhandle the stir bar, which is why i am suspecting old magnets.

 92 
 on: January 08, 2019, 04:15:11 PM 
Started by TheBlackBrainiac - Last post by TheBlackBrainiac
The combustion of 49.14 grams of a compound that contains only C, H, N, and O yields 84.49 grams of CO2
and 27.65 grams of H2O.
Another sample of the compound with a mass of 96.72 grams is found to contain 24.18 grams of O. What is the empirical formula of the compound?

 93 
 on: January 08, 2019, 02:49:45 PM 
Started by Apeng14 - Last post by Apeng14
How do convert this word problem into chemical equation:
1 mole of Nitrogen Monoxide reacts with Oxygen gas to produce Nitrogen Dioxide

 94 
 on: January 08, 2019, 01:13:44 PM 
Started by Shannon Dove - Last post by Borek
Sounds a bit like https://en.wikipedia.org/wiki/Miller–Urey_experiment

Technically there is no limit to the complexity of the molecules that can be produced, but the more complex ones have very low probability of being produced and of surviving in harsh conditions of the experiment, so in practice you wouldn't see anything too complicated.

 95 
 on: January 08, 2019, 01:09:06 PM 
Started by devcybiko - Last post by Borek
As for your point... "It is even worse than just solid styrofoam." - It actually is not worse than styrofoam as styrofoam is mostly air. Dissolving it in a solution decreases the area by about 99%. So, I can safely story 100x more styrofoam in the same space.

Acetone solution is much more flammable, much more volatile (and toxic when in air) and difficult to contain than the solid.

If it were really a good idea it would be long done on an industrial scale.

 96 
 on: January 08, 2019, 11:08:06 AM 
Started by Enthalpy - Last post by BobfromNC
My point is that ALL forms of energy are originally derived from the sun (or radioactivity, which was originally from a star...).   Solar power is current, but coal, oil, gas, biomass, etc are all just stored forms of solar produced biomass.   Even hydroelectric is indirect solar energy.   But hydrogen is not able to be mined, gathered, extracted, etc in any form that does not use more energy than is produced in the form of the hydrogen.  It is either electrolyzed from water, which wastes about 1/2 of the electricity in real life, or generated from steam-water-gas reactions, which involved burning fossil fuels.   So hydrogen is one of many ways to STORE energy, but it is not a source of energy, since it does not exist free in nature. 

If you can find a great way to make hydrogen from solar power, that would be a huge help, but for now, it is not a practical fuel for many tasks.   A new way to bioengineer algae, soybeans, or other crops to make more fuel per acre would be incredibly useful, as that could create a fuel more directly from the sun.  Or a better PV cell, but it is hard to compete with energy that was created and stored and concentrated in the ground for millions of years into a useful fuel. 

 97 
 on: January 08, 2019, 08:55:56 AM 
Started by Shannon Dove - Last post by Shannon Dove
If you take a simple compound like methanol and subject it to various forms of energy, such as ultrasound, ultraviolet, infared, high voltage low amperage DC electricity, high amperage low voltage high frequency ac electricity, etc, etc...what kind of molecules would form? Is there a limit to the complexity or is it possible that most any could form?  If you add aquas ammonium, could protein form, could alkaloids form?

 98 
 on: January 08, 2019, 07:20:27 AM 
Started by devcybiko - Last post by devcybiko
Thanks for all the feedback.

My plan for the solution is to keep it until the can fills up. Then let the plastic solidify and throw it away.

As for your point... "It is even worse than just solid styrofoam." - It actually is not worse than styrofoam as styrofoam is mostly air. Dissolving it in a solution decreases the area by about 99%. So, I can safely story 100x more styrofoam in the same space.

As for actual disposal - my plan is to deliver it to either a solvent recycling center or let it dry out and throw it in a landfill. It's a better solution than throwing styrofoam into a landfill.

 99 
 on: January 08, 2019, 06:55:42 AM 
Started by bootlegengineer - Last post by chenbeier
No explosives please, read forum rules.

 100 
 on: January 08, 2019, 06:28:35 AM 
Started by bootlegengineer - Last post by bootlegengineer
Im having trouble with determining proper solvents for activated carbon and sulfur. are either of them soluble in isopropyl alcohol? I'm trying to improve upon my method of making gunpowder. My current method is dissolving the nitrate salt in water and mixing the carbon and sulfur with isopropyl alcohol. I feel like I'm doing SOMETHING right because this method makes gunpowder that burns hotter and cleaner than any commercial gunpowder ive ever seen, but I still want to push further.

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