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ILLINOIS ACADEMY OF SCIENCE 



people will find it much more easily detected. We have 

 found it to be very satisfactory for use in titration of 

 the bicarbonate alkalinity of natural waters. Table 1 

 gives a typical series of results. 50 cc. of water were 

 used and duplicate titrations made with Methyl Orange 

 and the tetra-bromphenol-sulphonthalein. It will be 

 noted that the variation between the results obtained 

 with the two indicators is slight being practically no 

 greater than would be found between duplicate determina- 

 tions using the same indicator. The results tend to be 

 somewhat higher since there is a constant difference, it 

 could be eliminated by re-standardization of the standard 

 acid using the new indicator. It was found that the titra- 

 tion could be carried out satisfactorily by ordinary elec- 

 tric light although the daylight was to be preferred. 



TABLE I. 



CUBIC CENTIMETERS OF N/50 SULFURIC ACID TO NEUTRALIZE 

 50 cc. OF WATER 



B. P. B.=Tetra-brom-phenol-sulfonphthalein. 

 M. O. =Methyl Orange 



* No Methyl Orange results obtained by observer number two on 

 account of color blindness. 



