128 WILLIAM SEIFRIZ 



sists in giving the mixture of oil and aqueous solution ten violent shakes 

 by hand, then allowing the emulsion to rest for half a minute, when it is 

 again shaken. This procedure is repeated nine times. 



The oil used was the commercial "Pompeian" olive oil. The emulsi- 

 fiers were all aqueous solutions. Where the organic stabilizer is insolu- 

 ble in water, it was dissolved in some suitable solvent, such as alcohol, 

 and a colloidal dispersion made by pouring a small quantity of the alco- 

 holic solution into water. The emulsifiers were the following: the two 

 soaps, sodium oleate and sodium stearate; gelatose; gum arabic; the 

 glucosides: saponin, senegin and smilacin; the proteins, albumin from 

 egg, albumin from blood, casein and gliaclin; the lipoids, cholesterin and 

 lecithin, the alkaloid, cephalin; and an extract from plant tissue. To 

 these solutions was added a small crystal of thymol except in those 

 cases where the solution itself is aseptic. 



The electrolytes used, in reversing or in attempting to reverse the 

 emulsions were NaOH, NaCl, Na 2 S0 4 , BaCl 2 , CaCl 2 and Ba(OH) 2 . 

 The emulsions were thoroughly shaken after each addition of salt or 

 alkali. While no attempt was made to obtain in every case precise 

 quantitative measurements, yet the reversal point in all instances was 

 determined with reasonable accuracy. To ascertain the amount of 

 electrolyte necessary to cause reversal was not the main objective, but 

 merely to determine whether or not a reversal is at all possible with 

 certain emulsifiers and certain ions. 



We shall first concern ourselves with the type of emulsifier. Two 

 electrolytes only will, at the beginning, be considered in reference to 

 reversibility. The question whether other electrolytes have the same 

 influence as do NaOH and BaCl 2 , will be taken up after the question of 

 the type of emulsifier is disposed of. A further problem which developed 

 during the earlier experiments, namely, the possible influence of the 

 degree of acidity of the emulsions on their type and reversibility, is to 

 be discussed in a subsequent publication. 



Three methods were followed in determining the type of emulsion: 

 1, electrical conductivity; 2, color; 3, microscopical examination. 



The electrical conductivity method is based on the principle that 

 since water is the continuous phase in an oil-in-water emulsion, the 

 emulsion will conduct a current of electricity, while an emulsion of the 

 reverse type, since oil is the continuous phase, will not conduct an elec- 

 tric current. This method was first proposed by Clayton (5, p. 114) and, 

 has more recently been used with success by Bhatnagar (2). The type 

 of emulsion prevailing is ascertained by the reading of an ammeter. 

 The reversal point can be determined with considerable precision. The 

 method also has the advantage over the color method of telling in a 

 remarkable way what is happening in the emulsion. A higher or lower 



