SCIENCE— ADVERTISEMENTS 



Hydrogen Ion Indicators 



SORENSEN'S LIST 



Sorensen in an extensive investigation of the correspond- 

 ence between colorimetric and electrometric determinations of 

 hydrogen ion concentrations revealed discrepancies whicih are 

 attributed mainly to the influence of protein and salts. He 

 chose those indicators which were relatively free from the so- 

 called protein and salt errors. Sorensen's final selection, 

 together with P^ range of each indicator, is given below. 



Pg Bange 

 1 . Methyl Violet 0. 1- 3.2 



2. Diphenylamidoazobenzene 1 .2— 2. 1 



3. Metanil Yellow 1.2-2.3 



4. Tropaolin 00 1.4- 2.6 



5. Benzeneazobenzylaniline 2.3— 3.3 



6. Dimethylamidoazobenzol 2.9— 4.0 



7. Methyl Orange 3. 1- 4.4 



8. Benzene-azo-a-naphthylamine . . 3.7— 5.0 



9. A-napthylamine-azo-sulfanilic acid 3.5— 5.7 



10. Methyl Red 4.2- 6.3 



1 1. Para Nitro Phenol 5.0- 7.0 



12. Azolitmin app- 6.8 



1 3. Neutral Red 6.8- 8.0 



14. Rosolic Acid 6.9- 8.0 



15. Alpha Naphtholphthalein 7.3-8.7 



16. Tropaolin 000 7.6- 8.9 



1 7. Phenolphthalein 8.3-1 0.0 



18. Thymolphthalein 9.3-10.5 



19. Alizarine Yellow R 10.1-12.1 



20. Tropaolin 11. 1-12. 7 



By specifying National Stains and Indicators, you are 

 assured of receiving dyestuffs manufactured under expert super- 

 vision and subjected, prior to sale, to the most rigid chemical 

 and biological tests known. Catalogue upon request. 



National Stain and Reagent Co. 



NORWOOD, OHIO 



Gheiaicial Indicators and G.P. Organic Chemicals 

 Biological Stains and Beagents of Highest Quality 



— MADE IN V. S. A.— 



