324 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Its usefulness will depend upon its adaptability to the needs of the 

 analj'-st, and it may be modified to meet his conditions. For instance, 

 in the examination of beer, if the analyst must add the sample to the 

 reduction bottle without previous treatment, there should be adequate 

 provision for* the retention of hydrogen sulphide, the prevention of 

 frothing, etc. We are not at all sanguine of the success of the method, 

 however, unless the test solution has had adequate treatment before 

 reduction. 



During the study of the interference of sulphur, phosphorus, and 

 antimony, as given above, the possibility of quantitatively determin- 

 ing small amounts of these substances by this method, particularly of 

 antimony, suggested itself. We desire to note also that the principle 

 of allowing the gas to be tested to act along the surface of the react- 

 ing substance has a useful application in other cases, notably in the 

 determination of fluorine, and we are at present engaged in developing 

 a method for the estimation of small amounts of that substance 

 according to this principle. 



In conclusion, it gives us pleasure to acknowledge our indebtedness 

 to the C. M. Warren Fund of Harvard University for material assist- 

 ance in the preparation of the colored plates used in this article. 



Harvard University, Cambridge, Mass., U. S. A., 

 August, 1907. 



