TM     5-6630-215-12 until   the   amounts   of   turbidity   in   each   column   are   equal. Count    each 0.5   ml   addition   of   the   reagent   added. Mix   the   contents   of   the   tube after    each    addition    of    the    turbidity    reagent. Each   0.5   ml   addition   to the   50   ml   size   is   equal   to   (5)   Jackson   Turbidity   Units   (JTU). If  a  25 ml   size   sample   is   used, each    0.5    ml    additon    of    the    standard    turbidity reagent    is    equal    to    (10)    Jackson    Turbidity    Units    (JTU). See   the   com- pilation    below    (table    2-10). Rinse    both    tubes    carefully    after    each determination. j. Turbidity-Free    Water    Filter    Equipment. (1)    Equipment    (location    as    shown    in    fig.    1-6    and    assembled    for use   in   fig.   2-21). (2)    Preparation    of    Turbidity-Free    Water    and    De-Ionized    Water. (a)    Assemble    equipment    as    shown.    Make    sure    the    suction    end of   bulb   is   attached   to   suction   flask. NOTE Treated   and   filtered   water   may   be   used   in   lieu   of water    obtained    by    steps    (b)    thru    (e);    however, steps   (f)   and   (g)   should   be   completed. Table  2-10.  Turbidity  Calculations No.   of   Measured Amount 50  ml 25  ml Additions of  M1 Graduation Graduation 1 2 3 4 5 6 7 8 9 10 15 20 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 7.5 10.0 5  JTU 10  JTU 15  JTU 20  JTU 25  JTU 30  JTU 35  JTU 40  JTU 45  JTU 50  JTU 75  JTU 100  JTU 10  JTU 20  JTU 30  JTU 40  JTU 50  JTU 60  JTU 70  JTU 80  JTU 90  JTU 100  JTU 150  JTU 200  JTU (b)    Using    equipment    and    procedure    furnished    with    Chlorine Demand    and    Coagulation    Kit    coagulate    some    raw    water. (Jar   Test   Kit, para    2-22k). (c)   Allow   floe   in   jars   to   settle. (d)   Place   a   piece   of   filter   paper   on   top   of   perforated   plate in    filter    funnel. Change    1 2-82.1/(2-82.2    Blank)