136 WILLIAM SEIFRIZ 



Clowes (6, p. 423) states that while NaCl does not reverse the water- 

 in-oil emulsions it "undoubtedly promotes the formation of emulsions of 

 oil in water." If this is true, the effect is certainly exceedingly slight. 

 When 5 M NaCl is slowly added to a water-in-oil emulsion in which 

 gliadin is the emulsifier, no change is at first to be noted, either in the 

 (red) color or in the electrical conductivity of the original emulsion. 

 Not until 5 to 7 cc. of 5 M NaCl have been added to a water-in-oil 

 emulsion, with gliadin as stabilizer, is a slight reading of the milliam- 

 meter to be had. But the emulsion is still red, and therefore primarily 

 of the water-in-oil type. A microscopical examination reveals the 

 presence of a water-in-oil emulsion in which are scattered larger regions 

 of pure water, indicating a tendency toward separation of the two phases. 

 That NaCl tends rather to cause separation of the water and oil than to 

 promote the formation of an oil-in-water emulsion, is indicated further 

 by the behavior of soap emulsions in the presence of NaCl. 



It occasionally happens that an emulsion made with soap (0.001 M 

 NaCi 8 H350 2 ) as the emulsifier, is of the water-in-oil type, instead of the 

 usual oil-in-water form. This is the case when the soap solution 

 has stood for several days. There takes place a change in acidity, in 

 pH value, which seems to be an influencing factor. No matter what the 

 type, the sodium stearate emulsion is very sensitive to electrolytes. 

 When of the usual oil-in-water type (made with a freshly prepared soap 

 solution), a drop or two of M/10 BaCl 2 is sufficient to cause complete 

 reversal. If of the oil-in-water type (made from an old soap solution), 

 very little NaOH is also necessary to cause reversal. If NaCl tends to 

 promote the formation of a system of the oil-in-water type one would 

 expect that this influence would be readily detectable in so sensitive an 

 emulsion as is the one with a sodium stearate stabilizer. Such is not the 

 case, however. Two cubic centimeters or 5 cc. of 5 M NaCl does not 

 prevent the formation of a water-in-oil emulsion in which (an old and 

 therefore less alkaline solution) of sodium stearate is the emulsifier, 

 even though the emulsion is very sensitive to NaOH. 



Na 2 S0 4 is as ineffective as NaCl in causing reversal of the emulsions 

 studied, 



Discussion. If speculations on the behavior of the protoplasmic 

 membrane are to have any value, it would appear desirable to ascertain 

 if the reversal of phases by electrolytes of mono- and bivalent cations 

 is a phenomenon common to all emulsions. 



It was pointed out in the introduction of this article that Clowes' 

 hypothesis rests on three assumptions. For the purpose of discussion 

 the first two of these assumptions were considered as valid. The third 

 assumption has to do with the type of emulsifier. The question which 

 we can put to ourselves is this, Is the emulsifier that is active in proto- 



