PAPERS ON WATER SUPPLY 73 



than 50 parts of alkalinity to methyl orange, 71 less than 100, 

 89 less than 200. Only 10 had an alkalinity of over 200, and 

 only one of more than 300. A standard of 300 or less would 

 be very easy to maintain and a standard of 200 or less would 

 not be impossible. 



The total hardness was determined on 64 samples. Of 

 these 34 had a total hardness of less than 50; 45 less than 100; 

 57 less than 200. Only 7 had a hardness of more than 200, 

 and but 2 a hardness of more than 300. A limit of 300 would 

 be very easy to maintain and it should not be difficult to obtain 

 waters containing - less than 200. 



Sixty-six waters were examined for sulfates. Thirty-six 

 waters contained than 10 parts per million of S0 4 ; 42 less 

 than 25; 54 less than 50; 63 less than 100, and only 3 more 

 than 100. It should be apparently very easy to furnish waters 

 having less than 100 parts per million of sulfates. 



Ninety-nine samples were examined for iron. Eighty-six 

 of these contained less than .5 parts per million of Fe; 94 less 

 than 1.0; and only 5 had more than 2 parts per million. A 

 standard of less than 1 part per million would be very easy 

 to maintain and it would not be unreasonable to ask for .5 

 parts. 



Sixty-six samples were examined for lead and copper. Fifty- 

 six of these showed no trace of either metal; 7 contained .1 

 part per million; 2 contained .2, and 1 contained .3. It would 

 not seem difficult to maintain a standard of less than .3 or 

 even less than .1 part per million. 



One hundred samples were plated on gelatin and the num- 

 ber of colonies counted at the end of 48 hours. Of these, 29 

 samples had less than 99; 16 samples from 100 to 499; 16 

 from 500 to 999; 9 from 1,000 to 1,000; 9 from 2,000 to 

 ?,999, and 21 more than 10,000. 



One hundred and two samples were plated on agar and in- 

 cubated at 2>7y 2 ° for 24 hours. Forty samples showed less 

 than 50 bacteria per cc; 7 from 50 to 99; 8 from 100 to 199; 

 14 from 200 to 499; 8 from 500 to 999; 10 from 1,000 to 

 1,999; 10 from 2,000 to 9,999, and 5 had more than 10,000. 



While the large number of bacteria may consist for the 

 most part of harmless forms, the results would indicate un- 

 satisfactory conditions, either in the original water taken or 

 in the conditions of storage and delivery. 



The Commission on Standards have made no recommenda- 

 tion concerning the use of gelatin, but their standard of less 



