Franz Hofmeister

In 1902, Hofmeister became the first to propose that polypeptides were amino acids linked by peptide bonds, although this model of protein primary structure was independently and simultaneously conceived by Emil Fischer.

The order of cations is usually given as The mechanism of the Hofmeister series is not entirely clear, but seems to result mainly from effects on the solvent at higher salt concentrations (> 100 mM).

Early members of the series increase solvent surface tension and decrease the solubility of nonpolar molecules (salt out); in effect, they strengthen the hydrophobic interaction.

Repeated crystallization was a favourite purification technique in the early days of protein science, and was essential for its development.

Hofmeister also argued for peptide bonds based on the biuret reaction observed with all proteins but never with free amino acids.