THE COLLOID-CHEMISTRY OF SOAP MANUFACTURE 17 ! 



may be obtained by the cold process if 

 of sodium hydroxid is added quickly 

 and at once, the mixture is stirred 

 until it shows definite signs of stiffen- 

 ing and is then left to itself. 



Fig. 94 shows that when the cot- 

 tonseed oil is hydrogenated, when, in 

 other words, its oleic acid is converted 

 into stearic (and similarly, perhaps, 

 certain other unsaturated acids into 

 saturated ones) the " cold " process 

 no longer suffices to make soap. The 

 appearance of the first beaker on the 

 left in Fig. 94 must be compared with 

 that of the middle beaker in Fig. 93. 

 While no soap seems to have been 

 produced in the cold, saponification 

 of the hydrogenated fat is satisfactory 

 as soon as the reaction mixture is 

 heated for a time, as evidenced in the 

 second beaker from the left of Fig. 

 94. The same general truths are 

 brought out in the three right-hand 

 beakers of Fig. 94 in which, to mimic 

 accepted technical procedures more 

 perfectly, a sodium hydroxid of lower 

 concentration and a reaction mixture 

 containing a larger total of water were 

 used to accomplish saponification of 

 tin- hvdrogenated cottons* -ed nil. The 

 middle beaker of the whole- series 

 shows that saponification is a^ain im- 

 possible in t he " cold." A partial result 

 is obtained if the U-aker is heated t.. 

 above the liquefaction point of the fat 

 and the mixture is stirred; but to get 

 enmplete saponification the reaction 

 mixture must be kept, some time at 

 i hi- hitfh temperature as shown by 

 satisfactory result in the beaker on th< 



only the requisite amount 



me right of th 



