Hach DR/850, Procedures Manual, Page: 444 / 460

444
Standard Solution Method
Prepare a 500 mg/L volatile acid standard by using the TenSette
Pipet to add 0.8 mL of a Volatile Acids PourRite Ampule
Standard Solution (62,500 mg/L as acetic acid) to a 100-mL
volumetric flask. Dilute to volume with deionized water. Stopper
and invert to mix.
Method Performance
Precision
In a single laboratory, using a standard solution of 500 mg/L
volatile acids as acetic acid and two representative lots of reagent
with the instrument, a single operator obtained a standard
deviation of ±8 mg/L.
Estimated Detection Limit
The estimated detection limit for program 96 is 17 mg/L HOAc.
For more information on the estimated detection limit, see
Section 1 .
Summary of Method
The volatile acids test is designed specifically for the
determination of volatile acids in digestor sludges. The method is
based on esterification of the carboxylic acids present and
determination of the esters by the ferric hydroxamate reaction.
All volatile organic acids present are reported as their equivalent
mg/L acetic acid.
REQUIRED REAGENTS
Cat. No.
Volatile Acids Reagent Set (90 tests)............................................................................ 22447-00
Includes: (1) 2039-53, (2) 2042-53, (1) 818-42, (1) 2040-53, (1) 2038-32
Quantity Required
Description Per Test Units Cat. No.
Ethylene Glycol ......................................................... 3 mL.................1000 mL............ 2039-53
Ferric Chloride-Sulfuric Acid Solution .................... 20 mL................1000 mL............ 2042-53
Hydroxylamine Hydrochloride Solution, 100 g/L..... 1 mL...................100 mL............ 818-42
Sodium Hydroxide Standard Solution, 4.5 N ........... 4 mL.................1000 mL............ 2040-53
Sulfuric Acid Standard Solution, 19.2 N ................. 0.4 mL .................100 mL............ 2038-32
Water, deionized...................................................... 20.5 mL ....................... 4 L............ 272-56
VOLATILE ACIDS,
continued