Recent content by MrSid

  1. M

    Safe flea powder?

    It seems that you are basing your experimental powder on an existing labeled product and want to retro engineer it. While in grad school, I was witness to some high schoolers that my advisor had agreed to have us help with science fair ideas. One of the ideas used a video camera and T-maze to...
  2. M

    Airborne Spray that changes colour where Carbon Dioxide is present

    Ammonia will react with H2O and CO2 to make a white fog of ammonium carbonate or bicarbonate when all are present at appreciable quanties, but it is so hygroscopic that the xtals dissipate as small solution droplets that are essentially invisible. I would also steer clear of using aqueous...
  3. M

    Hints on this purification

    As hinted by chemistree, you should be talking about removing the byproduct of the EDC... We are also assuming that you (by some selectivity) did not get a complex mixture of the various benzoic esters of the sugar OH's, and the desired benzamide, that complicates things further (follow by TLC...
  4. M

    PH of a diluted solution

    A hint; take a look at the derivation of the HH equation and the simplifying assumptions that are made.... On the surface definition of a buffer, the pH is largely defined by pKa and has a broad largely unchanged pH over a range defined by the buffer's capacity. Dilution of the buffer only...
  5. M

    Hydrogen seperation from water

    The Wiki article describes PSA pretty well- it somewhat fits into the first method below for semipermeable membrane separation, but needs a driving force to release the adsorped molecules from the pores (usually atomic dimensioned channels in Xeolites). -semi-permeable membranes rely on pores...
  6. M

    Sheets of uranium?

    Reading this post's question of "home methods" in relation to radioactive materials, reminded me of an exercise that a senior scientist did with us in an industrial setting to sink home the dangers of radioactivity. A piece of paper, and a pen were handed to a gathering of us and each was told...
  7. M

    Medical Knee Injury

    I also have an injured knee that many years later was diagnosed via MRI as ACL tear and a torn meniscus injury. some thirty years later, it too also "goes out" and can prevent me from walking without a cane and a great deal of pain. Diagnosis is the first step... While in the appointment for...
  8. M

    Determining concentration of a particular substance in a solid?

    In short it isn't cheap and isn't easy... Cheap methods try to use a chemical reaction that is specific to the analyte and can be distinguished by vision (i.e. spectrophotometrically). Reactions that produce light and react enzymatically meet the issue of specific reaction and can be...
  9. M

    Determining concentration of a particular substance in a solid?

    For the item you are asking about, a weighed portion of the food (called an aliquot) is subjected to an extraction by a pure solvent to remove quantitatively the analyte (the acrylamide). A method that can detect the small amounts of the analyte is used to get a signal, and that is compared to a...
  10. M

    What does this notation mean?

    I believe Borek has it as these are the ways that superconductors and ceramics are often often described in "notation". Ceramics will be describing oxides with the noted molar composition of the XM, and superconductors will often use this , but have to describe the anionic components...
  11. M

    What does Nu- mean?

    You are getting it; I don't want to throw in a wrinkle but for polymerizations and for simple reactions that form only one covalent bond, the intermediate finds something else to act as a electrophile than another monomer unit. This reaction is known as a termination step in polymerization...
  12. M

    Question about silica

    silicon (the element) is generally reactive enough to become oxidized and change to silica, especially under geological conditions (don't expect to mine it or find it as the elemental ore). But it meets the definition of a material with specific molecular and crystalline properties known as mineral.
  13. M

    What does Nu- mean?

    Wiki spells it out in the beginning and the end of the article- the different nucleophilicity measures and equations aren't necessary for the concept. It does require a simple understanding of bond formation, and is narrowed to the covalent bonds formed with carbon in organic chemistry...
  14. M

    What does Nu- mean?

    In the insert drawing, the Nu- is water acting as a nucleophile and beginning the polymerization of the electrophilic double bond of the cyanoacrylate. The lone pair on H2O's oxygen acts as the partially negative charged nucleophile. The new partial negative charge is on the carbon alpha to the...
  15. M

    How to calculate the amount of CO2 needed to reduce the pH of a NaOH solution to 12.

    I suspect that if we were writing this as a problem to solve for a student, we would steer away from the complications of solubility and ionic strength by focusing on a weaker solution of NaOH, where the assumptions in the Henderson Hasselbach equation are followed. However, I do sometimes see...
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