MIXTURES CONTAINING BOKAX. 



41 



enough glycerin to amount to at least 30 per cent after the titration 

 is finished; then add phenol phthalein and titrate with N/5 sodium 

 hydroxid to the appearance of a permanent pink color. From the num- 

 ber of cc of soda used in the last titration the borax may be calculated. 

 The writer has found during the course of this work that the best 

 way to standardize the sodium-hydroxid solution is against a weighed 

 quantity of chemically pure Na.,B 4 O 7 10H 2 O, the titrations to be carried 



FIG. l. Apparatus for determining boric add. 



through in exactly the same manner as described above. Sometimes 

 the borax can not be dissolved directly from the sample and titrated 

 because of interfering substances. In such a case as this the method 

 following, as used in the food laboratory, Bureau of Chemistiy, is 

 applied. 



