PHASE REVERSAL IN EMULSIONS AXD IX PROTOPLASM 131 



Gelatose. This emulsifier was prepared by boiling 10 grams of 

 gelatin in 100 cc. of water for ten hours in a reflux condenser. The hot 

 sol was filtered through a tight plug of cotton wool. The solution thus 

 obtained is non-gelatinizable. A so-called WH Gold Label brand of 

 gelatin (supplied by Paul Putmann, Inc., New York) was used. Gela- 

 tose and olive oil produce an oil-in-water emulsion with a viscosity 

 30 times that of water. The amperage of the gelatose emulsion varies 

 from 92 to 116 milliamperes, averaging about 100. Reversal cannot be 

 produced in this emulsion by as strong a concentration as 10 cc. of M 

 BaCl 2 . As the volume of the aqueous phase in 50 cc. of emulsion was, 

 in all cases, 25 cc, the final concentration of BaCl 2 in the system was 



1000 X - - = 286 millimoles. This concentration, at which neither 

 35 



reversal nor "breaking" of the emulsion takes place, is more than 3,500 



times that necessary to reverse the soap (sodium stearate) emulsions 



mentioned above, and about 15,000 times as great as the concentration 



which Bhatnagar (3) finds necessary to cause reversal in the emulsions 



with which he worked. 



Saponin, senegin and smilacin. These saponin solutions were made 

 from Merck preparations. The saponin, senegin and smilacin were 

 dissolved in water at concentrations of 1 in 500. Each of these gluco- 

 sides produce oil-in-water emulsions which cannot be reversed by BaCl 2 . 



Gum arable. Ten grams of a fine, white, powdered gum arabic were 

 dispersed in 100 cc. of water. With this solution as an emulsifier the 

 resulting emulsion is of the oil-in-water type. The amperage of the 

 original emulsion is, with a 52 volt current, 78. On the addition of 0.1 

 cc. of M BaCl 2 the current rises to 81 milliamperes; and finally to 250 

 milliamperes when 10 cc. of M BaCl 2 have been added. The oil-in- 

 water emulsion with a gum arabic emulsifier is, therefore, irreversible 

 with BaCl 2 . 



Albumin. Two kinds of albumin were used, albumin from blood and 

 albumin from egg, both Merck products. Albumin readily forms an 

 oil-in-water emulsion in which the oil particles measure from 1 to 50/x. 

 The emulsion creams slowly, a barely noticeable aqueous layer being 

 formed at the bottom in 5 minutes. The viscosity of an emulsion made 

 from 1 per cent blood albumin is 9; from \ per cent egg albumin it is 

 4.6, as compared with 1 for water. The amperage at 52 volts is, in 

 1 per cent blood albumin, 91, and in \ per cent egg albumin, 39 milliam- 

 peres. An emulsion with either of the two albumins as the emulsifier 

 cannot be reverted by 10 cc. of M BaCl 2 in 50 cc. of emulsion. 



Casein. Casein well shaken in water and allowed to stand for an 

 hour gives a fine colloidal dispersion which readily emulsifies olive oil. 

 The emulsion formed is a water-in-oil one, and suddenly becomes stable 



