134 WILLIAM SEIFRIZ 



remain in a state of colloidal suspension for two or three days. It then 

 precipitates. Such an extract from spinach, diluted to one-half, forms, 

 with olive oil, a good oil-in-water emulsion, the oil particles of which are 

 from 1 to 50/x in diameter, averaging some 5 or 10/x. The emulsion has 

 a viscosity of 10.7 as compared with 1 for water. The current obtained 

 with 52 volts is high, being 235 milliamperes. Small quantities of M/10 

 to 10 cc. of M BaCl will not cause this emulsion to reverse. 



The influence of other ions on reversibility. We have seen 

 how highly speculative a theory may be when formulated on the behav- 

 ior of one type of emulsion. Equally misleading would it be to look 

 no further than the effect of a single group of ions. 



In considering the reversibility and irreversibility of the emulsions, 

 the influence of only two electrolytes BaCl 2 and NaOH, has so far been 

 considered, the former being used to reverse the emulsions of the oil-in- 

 water type and the latter to reverse those of the water-in-oil type. The 

 hydroxide of barium and the chloride of calcium were also tried upon 

 the oil-in-water systems, and two salts of sodium were tried upon the 

 water-in-oil emulsions. In every case CaCl 2 had the same effect on the 

 emulsions as did BaCl 2 , reversing the reversible ones and having no 

 effect on the irreversible ones. This was also true for Ba(OH) 2 , with 

 one exception, to be considered shortly. 



The fact that the hydroxide of barium will reverse the sodium oleate 

 emulsion in which the aqueous phase is the hydroxide of sodium, is 

 interesting because of its bearing on the relative importance of cations 

 and anions on reversibility. One-tenth cubic centimeter of saturated 

 Ba(OH) 2 (which titrated 0.194 M) has no apparent effect on 50 cc. of 

 sodium oleate emulsion in which M/10 NaOH is the dispersion medium. 

 Two-tenths cubic centimeter of the Ba(OH) 2 will reverse \ of the total 

 volume of the emulsion: 0.4 cc. will reverse slightly more than half: 

 and 0.7 cc. will reverse the entire 50 cc. of the emulsion into one of the 

 water-in-oil type. A high concentration of NaOH is now necessary to 

 bring the emulsion back into the oil-in-water type. One cubic centi- 

 meter of 10 M NaOH will reverse the emulsion into its original form. 

 The concentration of NaOH in the system is still not too high to prevent 

 a third reversal of part of the total volume of the emulsion. One cubic- 

 centimeter of saturated Ba(OH) 2 will reverse f of the already twice 

 reversed emulsion. That portion of the emulsion which has been 

 reversed for the third time is a good water-in-oil emulsion (microscopi- 

 cally examined), of high viscosity. 



Barium hydroxide will not only reverse all the emulsions which BaCl 2 

 will, but will also (partially) reverse one upon which BaCl 2 has no appar- 

 ent effect, namely, the emulsion in which gelatose is the emulsifier. 

 A saturated aqueous solution of Ba(OH) 2 (0.194 M) will reverse slightly 



