130 WILLIAM SEIFRIZ 



of saponification of the oleic acid in the olive oil by the NaOH in the 

 aqueous phase of the emulsion. The emulsion is made by shaking 25 

 cc. of olive oil with the same volume of the aqueous phase. Molar 

 and M/10 NaOH were used. The emulsion is quickly formed and is of 

 the oil-in-water type. The dispersed oil droplets measure from mere 

 specks of less than J/x, which are in active Brownian movement, to 

 globules 50> in diameter. The viscosity of the emulsion is 5.7 as 

 compared with a value of 1 for water. The current which will pass 

 through such an emulsion at 52 volts is 420 milliamperes in the case of 

 1M NaOH, and 100 milliamperes when M/10 NaOH is the aqueous 

 phase. On the addition of BaCl 2 the current falls. One would expect 

 a rise in amperage when the concentration of electrolytes in the continu- 

 ous aqueous phase is increased, and this is what takes place in those oil- 

 in-water emulsions which do not reverse. The fall in current in a soap 

 emulsion indicates a reduction in the volume of the electrolytic phase 

 which is available as a conductor for the current. This reduction, as 

 evidenced by the fall in amperage, is an indication that the emulsion is 

 reversing. Complete reversal of the M NaOH emulsion takes place when 

 1.2 cc. of M BaCl 2 has been added. The M/10 NaOH emulsion is 

 reversed with 0.3 cc. of M BaCl 2 , or 3 cc. of M/10 BaCl 2 . The milliam- 

 meter reads 0.00 after complete reversal has taken place. A very slight 

 reading, of some 3 milliamperes, may be obtained when the color of the 

 emulsion plainly indicates that there has been reversal. This is due to 

 an excess of aqueous phase which has not been caught in the water-in- 

 oil emulsion. If the emulsion is allowed to stand for a short time, less 

 than a minute, when the excess of free water settles in a small layer at 

 the bottom, no reading of the ammeter is to be had. 



Sodium stearate. This emulsion was prepared by adding the soap 

 directly to the aqueous phase. A M/1,000 concentration of sodium 

 stearate (NaCi 8 H 35 2 ) was used. A good emulsion is formed in which 

 the oil particles measure from 1 to 30 fx. The emulsion creams very 

 slowly. Its viscosity is 100 as compared with 1 for water. The emul- 

 sion is an oil-in-water one, and is readily reversible with BaCl 2 . Its 

 electrical resistance is high, the current passing through it, at 52 volts, 

 being but 3 milliamperes. It is very sensitive to electrolytes, requiring 

 but 0.2 cc. of a M/1,000 concentration of BaCl 2 , and but 2.0 cc. of a 

 M/10,000 concentration of BaCl 2 to reverse it. The water-in-oil 

 emulsion thus obtained by reversal can be readily reversed to its original 

 type by adding NaOH. It was possible, by alternate additions of 

 BaClo and NaOH, to reverse a sodium stearate emulsion nine times. 

 High concentrations of the two electrolytes were used to avoid too great 

 a dilution of the emulsion. One drop, 0.033 cc, of M BaCl 2 is sufficient 

 to reverse the original emulsion. 



