What is Impurities: Definition and 25 Discussions

Impurities are chemical substances inside a confined amount of liquid, gas, or solid, which differ from the chemical composition of the material or compound. Firstly, a pure chemical should appear thermodynamically in at least one chemical phase and can also be characterized by its one-component-phase diagram. Secondly, practically speaking, a pure chemical should prove to be homogeneous (i.e., will show no change of properties after undergoing a wide variety of consecutive analytical chemical procedures). The perfect pure chemical will pass all attempts and tests of further separation and purification. Thirdly, and here we focus on the common chemical definition, it should not contain any trace of any other kind of chemical species. In reality, there are no absolutely 100% pure chemical compounds, as there is always some minute contamination. Indeed, as detection limits in analytical chemistry decrease, the number of impurities detected tends to increase.Impurities are either naturally occurring or added during synthesis of a chemical or commercial product. During production, impurities may be purposely, accidentally, inevitably, or incidentally added into the substance.
The levels of impurities in a material are generally defined in relative terms. Standards have been established by various organizations that attempt to define the permitted levels of various impurities in a manufactured product. Strictly speaking, then a material's level of purity can only be stated as being more or less pure than some other material.

View More On Wikipedia.org

    I H2O/gold solution will not boil

    This is my solution and it remained still and did not bubble once while the pot boiled . I realise salt and oil impurities may increase the boiling point but I wouldn't imagine to this extent, and when I filtered the solution the oil seemed to collect the copper and other dissolved metals...
  2. Muhammad Usman

    I Concentration of Impurities in Extrinsic Semiconductor ?

    Hi, I was studying a book on analysis and design of analog integrated circuits. In the book it is mentioned as "For practical concentration of impurities, the density of majority carriers is approximately equal to the density of impurity atoms in the crystal" I researched about it and I found...
  3. D

    Effect of impurities on the boiling point of ethyl ethanoate

    After carrying out reflux and distillation to produce ethyl ethanoate (ethyl acetate) I measured the boiling point and I got 71 degrees Celsius whereas the true value is 77.1 degrees Celsius. Impurities increase the Boiling point (BP) as well as concentration. However my calculates BP is lower...
  4. F

    Identifying Manufacturing Impurities & Deliberate Doping in Metal Composition

    Hi. If a metal is very pure but still has other elements in it like this: -1 or 2 at 500ppm, 1 at 150ppm, 2 or 3 at 20-30ppm, 1 or 2 at 3-5ppm. Which are manufacturing impurities and which are deliberate doping? Are the 500ppm doping?
  5. W

    Naphthalene impurities spectroscopy

    Dear all, I was doing cleaning of naphthalene through zone refinement. After it is finished impurities from the naphthalene concentrate completely in one place of the ampule (lower part). I was interested to see which type of impurities are collected and did a spectroscopy measurement. Couple...
  6. B

    Donor Impurities and the Forbidden region

    Hello, I am doing my prep work for the 'Hall Effect' experiment that I will be doing next week in labs and have a question regarding the forbidden region between the valence band and the conduction band. I haven't taken any formal solid state physics, but this is 2nd year lab, if that helps...
  7. P

    How to dope a chemical compound?

    I am interested in creating phosphors for electroluminescent panels and from what I've read, one of the most common compounds is copper-doped zinc sulfide (ZnS:Cu). I've figured out how to create the zinc sulfide through a simple combustion synthesis reaction but it is the doping part that I...
  8. C

    Solid solution hardening, concentration dependence

    When you add impurity atoms to a material, the yield strength often increases by a process known as solid solution hardening. This is because the impurity atoms create a barrier to dislocation motion. The literature describing this phenomenon dates back to the 1960s with some famous papers by...
  9. f95toli

    DOS for impurities in a dielectric

    I have a question regarind how to calculate the DOS for ferromagnetic impurities in a dielectric We have samples with ferromagnetic rare-earth ions implanted in a dielectric material. The concentration known and is quite high but the ions are probably only interacting weakly (they are on...
  10. MarkFL

    MHB Mathematical Modeling Problem for 500-gal Aquarium Impurities

    Here is the question: I have posted a link there to this thread so the OP can view my work.
  11. S

    Removing impurities via recrystallization

    I have read online that suppose I am trying to purify compound_A, which contains an impurity, let's call that compound_B, that the solvent that I choose for recrystallization must either: 1) dissolve compound_A but not compound_B, so that compound_B can be filtered out after dissolving...
  12. A

    Investigating Possible Impurities on RBS Spectra of a Rhodium-Silicon System

    I was given a sample, that it is suppossed to be a medium thickness Rhodium on top of an infinite silicon waffer. The experimental RBS spectrum along with the simulation looks like that Apparently, there is another element(or maybe 2) that appear on the experimental spectrum. I am relatively...
  13. P

    Doping with impurities does what to Silicon?

    I want to know ... what happens to silicon when some impurity is added to it. Where does silicon goes??
  14. J

    Removing impurities using Na2CO3

    Homework Statement Why is the answer D?? Homework Equations The Attempt at a Solution So I know that Na2CO3 is used to remove excess acid but surely only HBr is the acid?
  15. S

    Effects of soluble impurities boiling and melting points

    In my textbook, it says that impurities lower the melting point and increase the boiling point. But is this only true if the boiling point of the impurity is greater than the boiling point of the solvent, and the melting point is greater than of the solvent too? So essentially, if greater...
  16. M

    Excitons bound to neutral impurities

    Hi all, I would like to understand the mechanism by which a neutral impurity can bind an exciton. Because the impurity is neutral the attracation can not be simply electrostatic. I know that there must be a "neutralising electyron (or hole)" in the machanism but things are not clear enough...
  17. Jadaav

    Impurities Impact Melting & Freezing: Explained

    "For a pure substance, melting occurs at the same temperature as freezing." Does it means that if impurities are added, then the melting point of the substance is not at the same temperature as freezing ? If yes, how you would explain this ?
  18. Y

    Impurities on melting point and boiling point of water

    When impurities was added to the water, it tends to increase the boiling point of the water to 102 degree celcius and lower the melting point of the water to -2 degree celcius! Why this happen? Is it because the impurities tends to absorb the heat supplied to boil the water causing it to take in...
  19. A

    Averaging over random potential of impurities

    Hey, In doing calculations on superconductors, I often hear that people say "averaging over the random potential of impurities make the theory translationally invariant both in time and space". I do not exactly understand it? Could you please explain it through a simple example or by citing a...
  20. N

    Why does half-filling in a lattice result in a zero chemical potential?

    Hi 1) I have read in an article that the atoms in a lattice are at "half-filling". As I understand, this means that the chemical potential is zero. Why does "half-filling" mean since it equals that the chemical potential is zero? 2) Let's say that I place an impurity with potential U0 in...
  21. Y

    Why impurities decrease melting points.

    anyone tell me why melting points of any substance decrease when we add any other material
  22. S

    Impurities effects in Type II SCs

    Hello, I have a question about how non-magnetic impurities affect the transition temperature in type II superconductors. I know that the impurities introduce additional scattering and therefore act to reduce Tc, but is there a simple formula that would relate the effect on Tc due to...
  23. P

    Mean free path and collisional cross section in Na due to impurities

    Let's say that we have Na at room temperature. The concentration of Na becomes plus one percent due to impurities. I'm interested in finding the mean free path and collisional cross section due to these impurities. I'm not sure on how Matheissen's rule could be applied, if we don't know what the...
  24. T

    Measuring Impurities in Iron for Blast Furnace

    might be a naive question, but concerning the blast furnace: they blow pure o2 through the raw iron to oxidise impurities like carbon etc, but that would mean that exactly the right amount of o2 would have to be blown through before the iron also started reacting, which in turn means the...
  25. recon

    Consequences of Air Impurities in Sulfur Burning

    The first step in the manufacture of sulphuric acid involves burning sulphur in air to produce sulphur dioxide. Why must the air used to burn the sulphur be as clean as possible? I'm not sure whether or not we should concerned ourselves with: 1. how the impurity affects the rate of...