HYDRO*! 





timate the II -ion concentration of the bod} flui 

 accuracy, provided certain precautions are taken I 

 disturbing influence which the protein and ^tlts in these flui 

 mi tin' color change. 



To understand this use of indicators, it is importanl to in mi 



thai one solution reacting neutral to one indicator H 



concentration which differs very marked]} from thai i 

 tion reacting neutral to another indicator. This is 

 read to differenl II ion concentral \ tlution thai 



phenolphthalein has a Pa of aboul 9, wh< ntral I 



ange lias a I'm of aboul 4. r l'liis can 1"- very clearly 

 a solution of phosphoric acid with decinormal alkali. After 

 amounl of alkali has been added it will be noticed that methyl 

 changes from red to yellow, bul after it has changed 

 alkaline as judged by this indicator, it still remains distinctly 

 wards phenolphthalein shows no red tint even thou, 

 more alkali is added. The methyl orange is. tin 

 sive i<» weak acids such as remain after the greater p 

 phoric acid has been neutralized by the alkali. 



The scries of indicators which has been empl< 

 given in the accompanying table, along with the I'm limits through wl 

 they change in color. 



List or [kdii 



CHF.MICAL NAMK 



COMMON 



SAMF, 





Thymol Bulfon phthalein 



id ran^c) 

 Tctrri liromo phenol sul- 

 d phthalein 



Orthn r.irlwxy benzene 



aao di methyl 



aniline 

 Ortho carboxy I 



nzo <li prop] 1 



aniline 

 l »i bromo ortho en 



sulfon phthalein 



Di bromo thymol soli 



phthalein 

 Phenol suit" ii phthalein 

 Ortho ereaol solfon 



phthalein 

 Thymol sulfon phtha] 



above) 

 Ortho ereaol phthalein 



Thymol blue 



Brom pi 

 blue 



Mi thyl 



purple 

 blue 































■ 



Thr<.f dyw n: 



