84 COLLOIDS IN BIOLOGY AND MEDICINE- 



pension and the electrolytes within certain limits, the greater is the 

 rapidity of flocculation. The dependence upon the concentration of 

 the electrolytes is especially noticeable in the vicinity of the elec- 

 trolyte threshold. Further away from the electrolyte threshold the 

 rapidity of flocculation is less dependent upon the concentration of 

 the electrolyte. (H. BECHHOLD.* 1 ) 



Under certain conditions, an excess of electrolytes may lead to 

 re-solution. This phenomenon is called peptisation. GRAHAM first 

 observed this occurrence upon treating ferric oxid gel with ferric 

 chlorid and compared it to the formation of water-soluble peptone 

 from coagulated albumin and hydrochloric acid. As a matter of 

 fact, peptisation probably depends upon a renewal of electric charge 

 by the excess of electrolytes. 



As has been shown by H. FREUNDLICH and his pupils ISHIZAKA 

 and SCHUCHT **, these facts furnish an indication that the more sen- 

 sitive a substance is to flocculation, the more will it be adsorbed. 



The great majority of colloids migrate to the anode, and on floccu- 

 lation the cation is of much the greatest importance ; the anion plays 

 but a subordinate role. The conditions are reversed in the case of 

 the few colloids which migrate to the cathode. However, R. BURTON 

 has shown that with increase of electrolyte concentration the rate of 

 migration of the colloid becomes constantly diminished and finally 

 the direction may change. At the stage when the concentration of 

 electrolytes is such that reversal occurs, in other words the isoelectric 

 zone, flocculation is most rapid. The increase in the action of the 

 cations is out of proportion to the increase in their valence. The 

 electrolyte concentration necessary for the flocculation of a mastic 

 suspension is FeCl 3 : BaCl 2 : NaCl = 1 : 50 : 1000. There are also 

 certain anomalies (see^H. BECHHOLD,* 1 as well as M. NEISSER and 

 U. FRIEDEMANN *) in connection with the rate of migration of the 

 ions, as well as in the electrolytic dissociation and especially in the 

 ionization pressure of electrolytes. In general the above relation 

 between the action of the cations is maintained. The powerful 

 flocculating action of the H ion without doubt depends upon its 

 high speed of migration while the OH ion has a corresponding action 

 upon colloids which migrate to the anode. 



Flocculation by means of trivalent iron and aluminium salts show 

 peculiar anomalies. These were discovered by M. NEISSER and 

 U. FRIEDEMANN* and also by H. BECHHOLD* 1 and called irregular series. 

 Later these phenomena of Inhibition Zones were followed further 

 by O. TEAGUE and B. H. BuxTON* 2 and also by A. LOTTERMOSER.* 

 An example from my published paper will best explain the phenom- 

 enon. XXX means strong flocculation, X X medium, X none. 



