124 



Scientific Proceedings (127) 



logical phenomenon, since patients were relieved of constipation 

 by the ingestion of milk fermented by B. Acidophilus. 



4. Relief from chronic constipation has persisted for six 

 months after the ingestion of B. Acidophilus has been discon- 

 tinued. 



5. Viable B. Acidophilus organisms in appreciable number 

 have been recovered from the feces of patients six months after 

 the ingestion of B. Acidophilus milk. 



61 (2021) 



Brom cresol green, a sulfonphthalein substitute for methyl red. 



By BARNETT COHEN. 



[From the Hygienic Laboratory, Washington, D. C] 



The sulfonphthalein indicators of Clark and Lubs have shown 

 themselves quite stable and reliable in biological fluids. Methyl 

 red, which is not a sulfonphthalein, is not altogether reliable, 

 but was included in the Clark and Lubs series because it was 

 indispensable in covering a certain range of H-ion concentration. 

 Methyl red is easily reduced irreversibly to a colorless com- 

 pound — frequently by mjicrobic action — thereby impairing its 

 utility as an indicator under all conditions. 



A sulfonphthalein indicator has been synthesized which has an 

 apparent dissociation constant almost identical with that of 

 methyl red and which seems as stable and reliable as the rest of 

 the sulfonphthaleins. This compound is tetra-brom m-cresol 

 sulfonphthalein. It is made by the bromination in glacial acetic 

 acid of m-cresol sulfonphthalein. The common name suggested 

 for this compound is Brom Cresol Green. Its effective range as 

 an acid-base indicator is between P H 4.0 and 6.0, with a color 

 change from yellow to green to blue-green. Its apparent disso- 

 ciation constant in terms of P„ is 5.00 (that of methvl red is 

 4.95). 



