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A reducing agent (also called a reductant or reducer) is an element (such as calcium) or compound that loses (or "donates") an electron to another chemical species in a redox chemical reaction. Since the reducing agent is losing electrons, it is said to have been oxidized.
If any chemical is an electron donor (reducing agent), another must be an electron recipient (oxidizing agent). A reducing agent is oxidized because it loses electrons in the redox reaction. Thus reducers are "oxidized" by oxidizers and oxidizers are "reduced" by reducers; reducers are by themselves reduced (have more electrons) and oxidizers are by themselves oxidized (have fewer electrons). A reducing agent typically is in one of its lower possible oxidation states and is known as the electron donor. Examples of reducing agents include the earth metals, formic acid, and sulfite compounds.
For example, consider the overall reaction for aerobic cellular respiration:
C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l)
The oxygen (O2) is being reduced, so it is the oxidizing agent. The glucose (C6H12O6) is being oxidized, so it is the reducing agent.
In organic chemistry, reduction more specifically refers to the addition of hydrogen to a molecule, though the aforementioned definition still applies. For example, benzene is reduced to cyclohexane in the presence of a platinum catalyst:
C6H6 + 3 H2 → C6H12
In organic chemistry, good reducing agents are reagents that deliver H2.
Historically, reduction referred to the removal of oxygen from a compound, hence the name 'reduction'. The modern sense of donating electrons is a generalisation of this idea, acknowledging that other components can play a similar chemical role to oxygen.

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  1. D

    Caleffi pressure reducing valve

    I have a caleffi valve on my system. It has worked well for some 10 years. Recently I noticed it is not regulating, with no flow sits at mains pressure. With flow it regulates. Replaced cartridge but just the same. It is a Caleffi 5350, i.e a static regulator. Any ideas as to why performance has...
  2. R

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  3. M

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  4. D

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  5. K

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  6. M

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  7. S

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  8. D

    Brass fitting, help needed to identifi the thread type

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  9. I

    Cold mains water hammer when taps are turn ON?

    The cold mains is in 22mm copper on a pipe run to to a bath and basin taps next to each other. The mains water is 4 bar static, no PRV or check valves. The bang happens seconds after the cold tap is turned on at either the cold bath or basin tap. There is a 0.5 litre potable water expansion...
  10. S

    pressure reducing valve cartridge leaking

    Hi all, I think the pressure reducing valve cartridge on my pressure reducing valve is leaking. The pipe size is 22mm. Where can I find a replacement for it? I am clue less about what pressure and type it is. here is a picture https://goo.gl/photos/3UeYrT7gdt3rmhgcA Thanks Seb
  11. JCplumb

    Basin mixer, high cold pressure, 0.5 bar hot (gravity HWS)

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  12. T

    Noisy taps

    Can anyone advise please: I have recently completed an en-suite and downstairs toilet refurb (DIY). The monoblock mixer taps I have fitted to both hand basins are very noisy. One was sourced from Victoria Plum and is rated maximum 3 bar...
  13. M

    Calculating pre-charge in CW expansion vessel..

    Anybody have a good way to calculate this please? Cold water expansion vessel on an unvented. Vessel is not ruptured, PRV is OK but every now and again it drips a bit. I suspect the vessel pressure is too high for the system...
  14. M

    15/22mm internal compression reducers

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  15. X

    water pump , press control and pressure reducing valve

    I have e residential water pumb with a press control on it. After it I placed a pressure reducing valve. The dimensions of the fittings of the press control and the pipes is 3/4 in. The pressuee reducing valve is 1/2in . Do you see a problem with that? I mean will the pump be stressed because...
  16. R

    Power flush

    Hi guys need some advice please on where I can hire a power flush unit "that's if they can be hired" and if so roughly how much would they cost, and also how difficult are they to get to grips with. I said I wouldn't go down this road but I have a couple of customers who need this done and I'm...
  17. A

    Water pressure reduction/regulation

    Hi all! I am new here, and I would really appreciate your help. I live in an area where the water pressure is high (>8bar) and unstable (may range between 6bar to 10bar). How can I regulate the pressure so that it is stable at around 6bar? Would a reducer do the job? Suppose a reducer reduces...
  18. P

    Reducing bushes for aluminium radiators

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  19. J

    unvented system problem!

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  20. S

    vibrating cold water supply pipe pressure reducing valve

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