88 ILLINOIS ACADEMY OF SCIENCE 



The three samples from impounding reservoirs in southern 

 Illinois all contained more than 0.1 part per million of man- 

 ganese. One of these contained as much as 7.5 parts per mil- 

 lion, on one occasion, the amount varying with the rainfall in 

 a surface water of this character. These reservoirs are fed by 

 small streams and springs. The figures indicate that they fre- 

 quently contain manganese. 



No apparent relation exists between the manganese content, 

 iron content and mineral content as indicated by the total re- 

 sidue on evaporation. 



The manganese content of water supply is important from 

 the practical standpoint, on account of the objectionable prop- 

 erties of manganese waters. In many respects they are similar 

 to waters which carry iron. They form black stains on white 

 plumbing fixtures and they turn fabrics which are washed in 

 them a yellow color. They cause serious trouble from incrus- 

 tation due to the separation of manganese dioxide. At the 

 Anna State Hospital the use of a manganese bearing water 

 has caused a hydrotherapy room, fitted with white enamel, tile 

 walls and fixtures, to become seriously stained. 



In conclusion, it may be said that the question of manganese 

 content should not be overlooked in the selection of a water 

 supply in Illinois. 



This work was carried out under the direction of Professor 

 Bartow, to whom the writer wishes to express his thanks. The 

 subject is being studied further with reference to the removal 

 as well as the further occurrence and method of determination 

 of the element. 



A COMPARISON OF METHODS FOR DETERMINING 

 DISSOLVED OXYGEN IN WATER AND SEWAGE 



F. W. MOHLMAN, UNIVERSITY OF ILLINOIS 



Dissolved oxygen determinations are of great value in the 

 control of sewage disposal plants and as an index of the purity 

 of the water in streams. Accuracy is necessary, but ease of 

 manipulation is also of importance. Although ,numerous 

 methods have been proposed, few have survived the tests of 

 practicability and accuracy. In the last report of the Com- 

 mittee of the American Public Health Association on Standard 

 Methods of Water Analysis, the Winkler method has been 

 chosen as the standard. The Levy method is an optional method 

 of the committee on standard methods of the American Public 



