1 normal acid or base (1N)
Biologists are sometimes confused by the non-standard[1] chemical unit of normality N. N refers in general to salts while it's most commonly used in the context of acid and bases. N can refere to either the cation or the anion in a hydrolysis. In the context of acid and bases it is generally assumed that N refers to the proton or the hydroxide ion.
- 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 |
1N, 2N HCl
1N HCl
- 10 ml fuming HCl (37% v/v = 10N = 10M)
- 90 ml H2O
2N HCl, see also [2]
- 20 ml fuming HCl (37% v/v = 10N = 10M)
- 80 ml H2O
Molarity (M) also a non-standard unit
For the nitpickers, molarity M is also a non-standard unit[3]. Expressing this explicitly as mol/L or mol/m3 is clearer to readers less versed in current biological customs.
