DISINFECTANTS, ETC. 141 



baryta ; filtering, when all the phenols are in the filtrate, 

 and are estimated as later described. The residue on the 

 filter contains the soaps and resins as barium compounds, 

 and the neutral oils. On shaking it up with acetone, the 

 neutral oils are dissolved out, and on filtration again, the 

 residue left, if treated with HC1, yields free fatty acids 

 and resins, which can be dissolved out with ether, the 

 ether evaporated, and the residue weighed. The acetone 

 filtrate containing the neutral oils can be examined for 

 these. 



Process. Take 10 grm. of disinfecting fluid, in a 

 300 c.c. Erlenmeyer flask. Add 100 c.c. of distilled water, 

 and shake well. Now add 15 grm. of barium hydrate 

 crystals, attach flask to a reflux condenser, and digest at 

 100 C. for half an hour by immersion in a water-bath, 

 shaking at intervals. Cool, and while cooling spread out 

 the soaps and resins with a glass rod. Decant off clear 

 liquid (baryta solution), or filter through an asbestos plug 

 by aid of water suction. In either case, wash out flask 

 with warm baryta solution, and decant after settling, or filter 

 into previous filtrate, making up bulk to 250 or 300 c.c. 

 exactly. Of the filtrate, 50 c.c. are taken in a separator, 

 HC1 is added till acid, and then some CaCl z . The liberated 

 phenols are extracted with ether. On separation the ether is 

 evaporated by putting the fluid in a tall glass flask, which 

 is put on a hot plate at 37 C., and evaporation encouraged 

 by blowing a current of air into the flask. The residue 

 is in this way also made water- free, and on cooling is 

 weighed in the flask. The weight of the flask is deducted, 

 and the remainder is the weight of phenol bodies present. 

 This is tested, as if it were pure phenol, by the bromine 

 absorption process. The residue is dissolved in NaOH, 

 excess of bromine solution in NaOH added, and then HC1. 

 The phenol present absorbs bromine. The amount of un- 

 used Br is measured by adding KI, and titrating the iodine 

 liberated in place of bromine, with N/io sodium thio- 

 sulphate solution. The difference from the amount of 

 bromine added (determined by a blank experiment) is the 

 amount of bromine absorbed. This multiplied by the figure 

 0-195, gives the equivalent amount of carbolic acid present. 

 Any notable difference of this amount from the weight of 



