SXJBSTITUTION OF BROM-THYMOL-BLUE FOR LITMUS 305 



The advantages of this medium are: 



1. Brom-thymol-blue includes the neutral point in its range 

 of hydrogen-ion concentration, so that the medium can be ad- 

 justed to exact neutrality before being inoculated. 



2. A medium containing sufficient brom-thymol-blue to act 

 as an indicator will not inhibit acid production. 



3. Brom-thymol-blue is not reduced by microbial action. 



4. The reaction of a carbohydrate medium containing brom- 

 thymol-blue can be recorded at any time during incubation. 



5. Changes in color with sUght changes in hydrogen-ion con- 

 centration are more marked with brom-thymol-blue than with 

 litmus. 



6. Brom-thymol-blue is easier to prepare than litmus. 



7. Heat does not affect brom-thymol-blue during sterilization. 



8. The reaction of carbohydrate broth containing brom- 

 thymol-blue can be read by artificial light, but this is impossible 

 with litmus. 



