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 on: Today at 03:43:55 AM 
Started by John Mcmurry - Last post by rolnor
The dione has very acidic hydrogens and would form a good nucleophile if base were added but it is also a excellent Michael-type alpha-beta unsaturated molecule and would probably polymerase very quickly under basic conditions, its a tricky startingmaterial.

 on: Today at 03:21:25 AM 
Started by fsonnichsen - Last post by Enthalpy
I'm confident that you can use either a four-electrodes or an induction setup over a wide range of conductivity. The limits of the meters you tested must rather result from their intended range, which the designer didn't bother to widen, or from the skills of the designer, since this needs both electromagnetism and analog electronics.

For the inductive measure:

Observe only the losses created by water conductivity. At 1000µS/m, 1% accuracy accepts j100µS/m from permittivity, and this effect is easily computed away afterwards. εr=80 allows F=22kHz, for which ferrite pots are excellent and let make coils with Q>100.

Build a resonant LC circuit at 22kHz, excite it and measure the decay time, or measure the voltage amplification when injecting a permanent excitation through a small capacitor. I take a water toroid of arbitrary h=20mm Ri=10mm Ro=15mm: at 1000µS/m its resistance is 785kΩ. If loading with the water sample shall drop its Q to 50, the necessary reactance is j16kΩ obtained at 22kHz by 120mH and 470pF, and the coil's equivalent series loss resistance must be << 320Ω while the parallel excitation and measurement circuit must apply >> 785kΩ.

Using an RM14 gapped for 1µH/turn2 (warning, this is not correct nor consistent, just for a quick check)
it takes 346 turns which, if Litz wire occupies 30% of 20mm2, have 28Ω resistance << 320Ω.
The N41 material offers Q=100 at 22kHz without gap, so the gap dividing the inductance by 6.8 brings Q=680 which is also >> 50. For accuracy better than 10% you must compare the Q loaded with water and unloaded.
The Q margin should allow to iterate the dimension design into something consistent.

For the resistive four-electrode measure, which makes simpler electronics:

Platinum isn't a must for water... Thin gold can be deposited on the copper of a printed circuit but is weak against abrasion. I guess graphite would do it too, and nickel as well - looks better than graphite, easy to clean, can be deposited by any subcontractor. Nickel is non-magnetic if its phosphorus content is >11% (or 15%?), which can be better at high frequencies due to the skin effect.

You could switch among a set of constant currents, or build a feedback: inject and measure the current needed to develop 100mV between the central electrodes.

I don't see a fundamental limit to the resistivity range here. It's more a question of design choices.

You might consider a capacitive measure too.

Build a capacitor whose dielectric is the water. A coaxial shape is less sensitive to EM perturbations and geometric tolerances. Operate at a frequency where the expected water is capacitive and the conductivity introduces losses, for instance 2MHz.

Build a resonant LC circuit for 2MHz, feed it through a small capacitor, measure the voltage amplification, deduce the losses and the conductivity.

I believe to have data about how constant water's conductivity is up to a few GHz, but didn't check it.

The capacitive design seems much more convenient than the inductive one: drop the capacitor in the water, instead of filling a toroid.

 on: Today at 03:02:34 AM 
Started by John Mcmurry - Last post by Babcock_Hall
Basically, it involves working backward from the product one step at a time.  Let's see what you can come up with...

 on: Today at 02:36:40 AM 
Started by John Mcmurry - Last post by John Mcmurry

 on: Today at 02:31:07 AM 
Started by John Mcmurry - Last post by clarkstill
It is a forum rule that you must at least show that you've attempted the problem.

Have you had any instruction on retrosynthesis?

 on: Today at 02:03:44 AM 
Started by John Mcmurry - Last post by John Mcmurry

Could anybody help me out finding the reagents for a succesful synthesis starting with cyclopent-4-ene-1,3-dione and ending with spiro[4.4]non-2-ene? I am totally lost on that one.


 on: Yesterday at 11:42:32 PM 
Started by boldfacebutton7 - Last post by sjb
Yes - is it, for instance anhydrous, hexahydrate? How does the total volume differ as you add the salt?

 on: Yesterday at 10:29:39 PM 
Started by boldfacebutton7 - Last post by boldfacebutton7
I am not sure what you meant by the type of Ferric Chloride. Do you want me to tell you the source of ferric chloride?

Yes, I was advised that calculation of Molarity is same irrespective of the solvent but my calculations do not match the one given in the paper.

 on: Yesterday at 08:15:32 PM 
Started by IBM - Last post by sjb
How many moles of M?

 on: Yesterday at 08:07:48 PM 
Started by sjb - Last post by sjb
This topic has been moved to Chemical Education.

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