this strong rosin soap solution were diluted with 

 water and treated while warm with varying quan- 

 tities of strong NaOH solution, so that part of the 

 sodium resinate was in each case salted out. The 

 solutions were placed in stoppered bottles and 

 allowed to stand overnight to come to room 

 temperature (20-23C.) and to assume a state of 

 saturation at that temperature. The solutions 

 were then filtered, giving clear, pale-yellow filtrates. 

 400 cc. portions were acidified and shaken with 

 . ether to determine the rosin content. The results 

 have been expressed in percentage strength of the 

 solutions in terms of rosin (present as soluble 

 rosin' soap). The figures also represent solubility 

 of rosin in grams per 100 cc. The balance of the 

 solution was in each case titrated with standard 

 H 2 SO 4/ using methyl orange as indicator. The 

 results represent the total alkali expressed in terms 

 of NaOH. The error due to the precipitation of 

 free rosin by the acid is practically negligible. 

 The actual causticity of the alkali varied from 95 to 

 97 per cent, small quantities of sodium carbonate 

 being unavoidably present. 



The results are not strictly accurate or com- 

 parable with one another. This is apparent, be- 

 cause of the presence of sodium carbonate in the 

 caustic solutions and because of the slight differen- 

 ces in temperature. Furthermore, the quantity of 

 soap precipitated out may have had some influence 

 on the solution itself, by reason of the colloidal 

 tendency of sodium resinate. However, the general 

 effect of increasing the strength of the caustic soda 

 is quite apparent. The solubility of rosin soap in 

 1 per cent NaOH amounted to several grams per 

 100 cc., and for this reason was not determined. 

 In 1.98 per cent NaOH the solubility was 0.4817 

 grams per 100 cc., while in 3 . 33 per cent caustic 

 it dropped to 0.1445 grams. After a concentration 

 of about 4 per cent NaOH was reached there was 

 no pronounced decrease in solubility of the rosin 

 soap; 10 per cent NaOH gave no more complete 

 precipitation than 7 per cent caustic. This shows 

 that rosin soap can be effectively salted out by 

 strengthening the solution to 4 per cent NaOH 



20 



