(1) Notes on colloidon membranes for ultrfiltration and pressure dialysis / by G.S. Walpole. (2) Detection and concentration of antigens by ultrafiltration, pressure dialysis, etc., with special reference to diphtheria and tetanus toxins / by A.T. Glenny and G.S. Walpole.

  • Walpole, George Stanley.
Date:
[1915?]
Catalogue details

Licence: In copyright

Credit: (1) Notes on colloidon membranes for ultrfiltration and pressure dialysis / by G.S. Walpole. (2) Detection and concentration of antigens by ultrafiltration, pressure dialysis, etc., with special reference to diphtheria and tetanus toxins / by A.T. Glenny and G.S. Walpole. Source: Wellcome Collection.

    20/30 (page 300)
    further purification serves no useful purpose: it may be inadvisable, in fact, for one would suspect, on the ground of general experience, an increased instability of the toxin as it approaches purity. The essential process we have employed to concentrate and purify diphtheria toxin is to dialyse it under pressure using a collodion membrane of a particular kind dealt with more fully, for the sake of convenience, in a separate paper [Walpole, 1915]. The dialysed material is then acidified and centrifuged. The precipitate, dissolved in a trace of alkali, constitutes the concentrated material. It should be kept in the cold after the addition of a small quantity, say, 0-3 per cent., of phenol. To know when the material has dialysed sufficiently to pass on to acidi¬ fication either of the following methods may be used. A sample may be tested by adding 0*3 cc. N acetic acid to 10 cc. If the precipitate formed flocculates well and leaves a bright supernatant fluid no further dialysis is necessary. This point corresponds, for the broths which have been dealt with, to that where no more colouring matter passes out through the walls of the bag and to a conductivity of about 0*00078, i.e. that of 0*0065 N KOI. For routine work with a continuous apparatus [Walpole, 1915, p. 290] rough conductivity determinations are much the most convenient method for checking the working and determining how much dialysed toxin may be drawn off each day in safety. jResults. Where this process is applied the cost of toxin production is considerably reduced, for batches are always worth the units they contain, whether they are good or bad, and no toxin however poor need be thrown away. Periodic recurrences of bad toxin to which every laboratory is subjected need, there¬ fore, no longer be feared. The following generalisations summarise the results of our experience upon which this concentration process for diphtheria toxin had been developed. 1. Whether by pressure dialysis or ultrafiltration no toxin passes through these membranes. These results have been checked so many times that special experiments need not be cited. Part of the evidence supporting them will be found in the ensuing pages. [See also Walpole, 1915, p. 288.] As a matter of convenience, however, the details of some routine con¬ centrations are given at this juncture, for they depend essentially upon the impermeability of these bags to diphtheria toxin.