EMULSOIDS 395 



with water, thus indicating a tendency for close association 

 between the substance and its solvent ; for this reason the 

 term Lyophilic colloid has been employed by some authors to 

 designate these substances ; the term Lyophobic being, by 

 contrast, applied to the suspensoids. 



Emulsoids are in fact regarded as consisting of a liquid 

 disperse phase composed of a concentrated solution of the 

 substance suspended in a liquid continuous phase composed 

 of a much diluter solution. The term emulsoid, has been 

 adopted to indicate their general relation to the emulsions 

 which likewise are two-phase systems produced from two 

 liquids which are immiscible. 



GENERAL PROPERTIES OF EMULSOIDS. 



The outstanding feature of the emulsoids as compared 

 with suspensoids is their much greater viscosity ; this fact, 

 however, is not surprising if the views put forward with 

 reeard to their constitution are correct, since true emulsions are 

 known to have high viscosities, e.g. Mayonnaise sauce. The 

 viscosity of a solution varies both with the concentration and 

 the temperature ; it is liable to be influenced by a variety of 

 causes such as prolonged heating and by different methods of 

 treatment. In some cases the passage through a capillary 

 tube will alter the viscosity of a solution and in some instances 

 the viscosity will diminish spontaneously. Viscosity is, more- 

 over, considerably affected by the presence of dissolved salts, 

 being increased by sulphates, phosphates, and citrates but 

 reduced by iodides or sulphocyanides. 



(a) Optical Properties. — These are in many respects less 

 striking than those of the dispersoids since emulsoid sols, 

 although frequently opalescent or turbid, are not as a rule 

 highly coloured. The presence of the diffracting particles of 

 the disperse phase may, however, in some cases cause a 

 bluish opalescence as, for example, in a starch solution ; in- 

 deed, according to Bancroft,* the blue colour t of eyes and 



* Bancroft : " J. Phys. Chem.," 1919, 23, 356, 365. 



t According to Wo. Ostwald, the blueness of the sky is similarly due 

 to the atmosphere being composed of matter in a disperse phase suspended 

 in a continuous phase. 



