Page "learned" Paragraph 146

For protein identification, fractions from the column were concentrated by pervaporation against a stream of air at 5-degrees-C or by negative pressure dialysis in an apparatus which permitted simultaneous concentration of the protein and dialysis against isotonic saline.

During the latter procedure the temperature was maintained at 2-degrees-C by surrounding the apparatus with ice.

Because negative pressure dialysis gave better recovery of proteins, permitted detection of proteins concentrated from very dilute solutions and was a gentler procedure, it was used in all but the earliest experiments.