Biological Survey — Erie-Niagara Watershed 



109 



conduct such additional determinations as biochemical oxygen 

 demand, nitrogen ratios, and non-carbonate hardness when 

 desirable. 



Analytical methods followed were essentially as outlined in 

 ''Standard Methods of Water Analysis", 6th edition, 1925, Amer- 

 ican Public Health Association. Ten day biochemical oxygen 

 demand was determined by incubation at 20° C. with dilution 

 where necessary. All values for percentage saturation of dis- 

 solved oxygen have been adjusted in accordance with the baromet- 

 ric pressures of the regions. The heavy horizontal lines across 

 the graphs represent 100 per cent of saturation. 



Dr. Peter R. Kosting, assistant chemist, United States Fixed 

 Nitrogen Research Laboratory, was associated with the writer 

 tliroughout the summer's work. 



A portable outfit for field work in pollution studies 



All data are listed in the accompanying tables, while a few 

 series have been selected for graphical representation. Alkalinit}^ 

 values are expressed as parts per million of calcium carbonate in 

 all cases. The phenolphthalein end point having been accepted as 

 the dividing line between free and fully bound or fixed carbon 

 dioxide, the latter content, or as otherwise expressed content of 

 normal carbonate is given by twice the phenolphthalein alkalinity. 

 Total alkalinity as determined with methyl orange, minus twice 

 the phenolphthalein alkalinity gives the bicarbonate (half bound 

 carbon dioxide) expressed again as calcium carbonate. Such 

 values may be converted into terms of bicarbonate by multiplying 

 with the factor 1.62. 



