The elements of colloidal chemistry / by Herbert Freundlich, translated by George Barger.

  • Herbert Freundlich
Date:
[1925?]
Catalogue details

Licence: Public Domain Mark

Credit: The elements of colloidal chemistry / by Herbert Freundlich, translated by George Barger. Source: Wellcome Collection.

    18/244 page 6
    of a space-lattice by imagining a large number of uniformly woven nets arranged parallel to each other at regular intervals. At each knot in the network there is an atom, in the case of sodium chloride alter¬ nately a sodium ion and a chlorine ion. The distance between two points of the space-lattice in sodium chloride is about 0-3 millionth of a millimetre. The mutual arrangement of the points of the space-lattice varies with the crystal form of the solid. All the structural units which have so far been considered, viz. molecules, atoms and electrons, are smaller than one millionth of a millimetre (1 /u/li = o-ooooooi mm.). There are, however, many structures in which we must take larger units into account, and these all belong to the colloids. We know there are, for instance, solutions which differ from ordinary ones in that their solute will not pass through parchment paper, collodion, etc. Thus if we place an aqueous solution of sugar or of sodium chloride in a sack of parchment paper, the sugar and the salt gradually pass through the membrane. This is, however, not the case when a solution of gelatine or of starch is similarly treated. We have every reason to assume —and other observations confirm this—that in the latter solutions there are much larger solution aggre¬ gates than in those of sugar and of salt. The molecules of these substances pass through the pores of the membrane, whilst the particles present in gelatine and starch solutions are unable to do so. In this way Graham was led in 1861 to differentiate solutions
    digitised image 1
    digitised image 2
    digitised image 3