PAPERS ON WATER SUPPLY 



77 



found to contain arsenic, but apparently in rather small 

 amounts. 



The results from the samples obtained from the purification 

 plants are given in a table. In all cases the arsenic is recorded 

 as arsenic trioxide, As 2 :i . Five gram samples of the alum 

 were used, as this amount gave stains best suited for com- 

 parison with the standards. Quincy and the Rock Island 

 Arsenal each submitted samples from two different manu- 

 facturers, therefore twenty-three samples from twenty-one 

 places were examined. 



TABLE I. 



ARSENIC AS As 2 3 IN FILTER ALUMS USED IN ILLINOIS 



Arsenic as As 2 8 

 City Pts. per mil Percent Gallons* 



Cairo 1.6 .00016 3213 



Carlinville 1.8 .00018 2856 



Charleston 1.2 .00012 4283 



Chicago and Rogers Park 1.4 .00014 3671 



E. St. Louis and Granite City.... .8 .00008 6425 



Decatur 1.4 .00014 3671 



Elgin 1.6 .00016 3213 



Ft. Sheridan 1.2 .00012 4283 



Hamilton 1.4 .00014 3671 



Kankakee .8 .00008 6425 



Kenilworth 1.4 .00014 3671 



Lawrenceville 3.0 .00030 1713 



Macomb 1.6 .00016 3213 



Moline 1.0 .00010 5140 



Mt. Carmel 2.0 .00020 2570 



Mt. Vernon 1.2 .00012 4283 



Pana 1.2 .00012 4283 



Quincy 1.0 .00010 5140 



Quincy 4.0 .00040 1285 



Rock Island 2.0 .00020 2570 



Rock Island Arsenal 1.6 .00016 3213 



Rock Island Arsenal 1.0 .00010 5140 



Streator 3.4 .00034 1512 



♦Gallons of water containing a minimum medicinal dose of 2 

 mg. when the water is treated with 6 grains of alum per gallon, 

 provided that all the arsenic remains in solution. 



The results obtained by analyzing alum used in Illinois clear- 

 ly show that arsenic in exceedingly small amounts is always 

 present in filter alums. We find a minimum of 0.8 parts per 

 million (.00008 per cent) and a maximum of 4.0 parts per 

 million (.0004 per cent) of arsenic as As 2 3 in the alum used 

 by Illinois water purification plants. If a water were treated 

 with alum containing the maximum amount of arsenic found 

 at a rate of 6 grains of alum per gallon, an amount which is 

 very seldom exceeded, and if all the arsenic were soluble and 

 remained in the filtered water, since arsenic is not an accumu- 

 lative poison, a person must drink 1285 gallons of the treated 



