PHASE REVERSAL IN EMULSIONS AND IN PROTOPLASM 133 



emulsion formed is of the oil-in-water type, the oil particles of which 

 vary from 1 to 8 or 10m (relatively few larger) in size, the smaller ones 

 being in active Brownian movement. The milliamperage of the emul- 

 sion, with a 1 per cent lecithin aqueous phase, is 30. Ten cubic centi- 

 meters of M BaCl 2 raise the amperage to 320 milliamperes, which means 

 that the emulsion is still of the original oil-in-water type. The oil 

 emulsion with lecithin emulsifier is, therefore, irreversible with BaCl 2 . 



Cholesterin. Cholesterin is generally included among the "lipoids". It 

 is more true to the character of fatty substances than is lecithin, being 

 lyophobic. An aqueous colloidal dispersion of cholesterin was made by 

 first dissolving 2 grams in 100 cc. of absolute alcohol boiled in a reflux 

 condenser, and dispersing 1 cc. of this 2 per cent alcoholic solution in 

 99 cc. of water, and finally filtering. This 0.02 per cent aqueous disper- 

 sion of cholesterin emulsifies olive oil very quickly into a water-in-oil 

 emulsion of high viscosity. 



It is remarkable how precisely these cholesterin emulsions will emulsify 

 at exactly the same point in the process of shaking when the emulsions 

 are made from the same lot of material. Of three cholesterin emulsions 

 made up at the same time two emulsified on the 55th shake and one on 

 the 58th. The pauses between every tenth shake were, in these three 

 emulsions, \ minute in the first case, 1 minute in the second case, and 

 5 minutes in the third case. The length of the pause, if above a certain 

 minimum, is apparently of little or no influence. 



No current, at 52 volts, passes through the original water-in-oil choles- 

 terin emulsion. The emulsion is readily reversible with NaOH. One 

 drop (0.033 cc.) of M NaOH, or 0.3 cc. of M/10 NaOH, is sumcient to 

 reverse the emulsion. BaCl 2 will reverse the oil-in-water emulsion 

 obtained with NaOH, back into the original type, and NaOH will 

 again cause reversal into an oil-in-water emulsion. 



Cephalin. The alkaloid cephalin was used in a concentration of 1 :500 

 as an emulsifier. With this solution as the aqueous phase a good water- 

 in-oil emulsion is obtained. Complete reversal results on the addition 

 1.0 to 1.5 cc. of M/10 NaOH. This oil-in-water emulsion can be 

 reversed back to the original form by 0.3 cc. of M/10 BaCl 2 . One 

 cubic centimeter of the M/10 NaOH will again reverse the emulsion, and 

 2.0 cc. of M/10 BaCl 2 will again bring it back. As the emulsion is 

 reversed again and again higher concentrations of the salt and the base 

 are necessary to cause complete reversal. Finally, the emulsion 

 "breaks,' - ' that is, separates into two layers, of oil and water respectively. 



Plant extract. A quantity of fresh spinach was run several times 

 through a coarse and then a fine mincer. The pulp thus obtained was 

 subjected to high pressure. A large quantity of plant juice, consisting 

 of protoplasm and cell sap, is pressed out. This plant extract will 



