BioConcepts

colloidKolloid (ger.)

• Applied by Graham, 1861, to describe a peculiar state of aggregation in which substances exist; opposed to crystalloid. Substances in the colloid state are characterized by little or no tendency to diffuse through animal membranes or vegetable parchment, do not readily crystallize, are inert in their chemical relations, but are highly changeable. So called because gelatin may be taken as the type of the class. (OED 2012)
  category molecular biology

  1860

  Much value is attached to diffusion, as affording the means of bringing out clearly, and subjecting to numerical expression, the distinctive properties of what appear to be two great divisions of chemical substances. The first, or diffusive class of substances, are marked by their tendency to crystallize, either alone or in combination with water. When in a state of solution they are held by the solvent with a certain force, so as to effect the volatihty of water by their presence. The solution is generally free from viscosity, and is always sapid. Their reactions are energetic and quickly effected. This is the class of crystalloids. The other class, of low diffusibility, may be named colloids, as they appear to be typified by animal gelatine. They have little if any tendency to crystallize, and they affect a vitreous structure.

  Graham, T. (1861). Liquid diffusion applied to analysis [Abstract] Proc. Roy. Soc. London 11, 243-247: 243.

  1861

  Certain liquid colloid substances are capable of forming a jelly and yet still remain liquefiable by heat and soluble in water. Such is gelatine itself

  Graham, T. (1861). Liquid diffusion applied to analysis Philos. Trans. Roy. Soc. London 151, 183-224: 184.

  1875

  Matter has two solid states, distinguished as crystalloid and colloid; of which the first is due to union of the individual atoms or molecules, and the second to the union of groups of such individual atoms or molecules.

  Spencer, H. (1862/67). First Principles: 295 (§101).