APPLICATION OF ‘t BLEACH ” O27 
Different means may be used to determine the amount of available 
chlorine which is being added to a water supply. The “‘ bleach’ may 
be analyzed for available chlorine to determine its strength in per cent. 
Calculations may then be made to find how much should be added 
to the mixing tanks. Lewis (1912) reports the following scheme used 
at Evanston, IIL: 
N=No. of gallons pumped per minute. 
aM , or number of minutes to pump 1,000,000 gals. ; 
@=WNo. of pounds of “ hypo ” to be added to each 1,000,000 gals. 
of water. 
=P, or pounds of “‘ hypo ” to be added cach minute. 
= No. of gallons of liquid to be added per minute. 
bay |O 
X=pounds of “hypo” in 1 gal. of solution. 
Changes in the rate of pumpage demand a change in the amount of 
chemical which is applied. This is easily accomplished by changing the 
size of the orifice. 
If the strength of the bleach solution is determined from that in the 
orifice box the following scheme will indicate how much is being applied 
to the water. 
RX70=p.p.m. available chlorine; 
R=No. of cubic centimeters of N/10 NaaSeO3 used per 50 c.c. 
of bleach solution. 
Parts per million of available chlorine in the filtered water equals 
Gal. bleach solution bed 
i P-P-M-* Gon of water pumped’ 
Analysis of the dry bleaching powder which is necessary in the above 
method, is accompanied by certain errors. To obviate these, the bleach 
solution may be mixed in the usual way and samples removed directly 
from the orifice box. This procedure has the advantage that it is more 
direct—indicating the actual amount of available chlorine which is 
being applied to the water. The following calculations may be used: 
