1 normal acid or base (1N)
Revision as of 11:45, 8 December 2010
Biologists are sometimes confused by the non-standard chemical unit of normality N. N refers in general to salts while it's most commonly used in the context of acid and bases.
- 1 M (mol/l) = 1 N for an acid that releases 1 proton* when dissolved in water, e.g. HCL (*monoprotic)
- 1 M (mol/l) = 2 N for an acid that releases 2 protons*, e.g. H2SO4 (*diprotic)
For example, some antigen retrieval methods use 2N hydrochloric acid to open up the tissue to allow antibody binding. This could be a nucleotide analogue, as BrdU or dUTP-TMR in cell proliferation of apoptosis assays.
|acid/case||molecular weight||N vs M|
|HCl -> 1·H+ + Cl-||36.5 g/mol||1N = 1M = 36.5g/L|
|H2SO4 -> 2·H+ + SO42-||98 g/mol||2N = 1M = 98g/L|
|NaOH -> Na+ + 1·OH-||40 g/mol||1N = 1M = 40g/L|
By the way, molarity M is also a non-standard unit. Expressing this explicitly as mol/L or mol/m3 is clearer to readers less versed in current biological customs.