118 SOAPS AND PROTEINS 



Molar equivalents of the different sodium soaps (1/10 mol) were 

 dissolved in equal volumes of water (1000 cc.) and the whole 

 brought into homogeneous solution at the temperature of a boiling 

 water bath. Enough salt was then added at the high temperature 

 so that on cooling the mixture to 18 C. a first separation from 

 the pure dispersion medium (salt water) was observed. It will 

 be noticed that as the acetic series is ascended, a lower and lower 

 concentration of sodium chlorid is required to bring about such 

 separation. While in the concentrations of soap employed, 

 sodium caprylate did not come out in even a saturated (over 

 5 molar) sodium chlorid solution, sodium stearate separated from 

 the dispersion medium when less than a 1 molar sodium chlorid 

 concentration prevailed. 



A second series of experiments to illustrate these general 

 truths is presented in Table LV and Fig. 76. While the arrange- 

 ment in these experiments is intended for use under another 

 heading later, the findings fit in at this point. The experiments 

 show the effects of adding the same volumes of increasingly con- 

 centrated sodium hydroxid solution to equimolar amounts of 

 the different fatty acids of the acetic series, only those members 

 being used in which soap formation takes place at ordinary room 

 temperature. (Soap is produced, in other words, by the so-called 

 cold process.) 



Fig. 76 and Table LV show that only clear solutions are 

 obtained in the case of formic and acetic acids. At the same 

 molar concentration, sodium propionate begins to be salted 

 out in the higher concentrations of the sodium hydroxid. As 

 we pass to the sodium butyrate, sodium valerate, sodium caproate, 

 sodium caprylate, sodium caprate and sodium laurate, the salting- 

 out effect moves little by little to the left. The experiment 

 again shows therefore that a soap of the acetic series is salted out 

 with increasing ease (by sodium hydroxid, in this instance) as we 

 ascend the series. 



Fig. 76 and Table LV illustrate, however, a second point pre- 

 viously commented upon. It will be observed that beginning 

 with sodium butyrate and going up in the chemical series one or 

 more tubes are filled with solid gels. This is because, as we ascend 

 the series, soaps of an increasing gelation capacity are produced. 

 The final picture seen in the photograph is therefore the 

 composite represented by (a) the production of soaps possessed 



