A simple method of checking for interference by aluminum is to first read the concentration one minute
after mixing with the SPADNS reagent. Then wait 15 minutes and read it again. An appreciable increase
in the reading indicates the presence of interfering aluminum. If this is the case let the treated sample sit
undisturbed for two hours. Then make another reading. This procedure will eliminate the effects of up to
3.0 mg/l of aluminum.
Refer to para 2.6.2 for shut down of the Spectrophotometer.
184.108.40.206. Ferrous Iron Test.
Purpose of Test: To determine the amount of ferrous iron present in water.
Range: 0.0 to 2.0 mg/l
Equipment Used: Found in Main Carrying Case, para 1.8, fig. 1-1
Spectrophotometer, (20), fig. 1-1
Ferrous iron reagent, (23), fig. 1-1
Graduated cylinder, (31), fig. 1-1
General Techniques Used: Refer to paragraphs cited below as required by procedure.
Planning the Test, para 220.127.116.11
Cleaning Glassware, para 18.104.22.168
Handling and Storing Reagents, para 22.214.171.124
Collecting Water Samples, para 126.96.36.199
Mixing, para 188.8.131.52
Using Graduated Cylinders, para 184.108.40.206
Spectrophotometer, para 220.127.116.11
High voltage used with Spectrophotometer. Misuse can cause electrical shock and damage
equipment. When operating with 115V or 220V power, make sure the power source and
equipment are in ground potential. Ensure that the power cable connections are correct for the
desired voltage power before connecting the power source.
Samples should be analyzed as soon as possible after collection to prevent oxidation of ferrous
iron to ferric iron.
Iron reagent powder pillows are stable up to 48 months depending on storage and handling
conditions. A cool, dry atmosphere gives the longest shelf life. The iron reagent powder can be
checked by adding the contents of one pillow to about 25 ml of water that contains visible rust.
If an orange color does not develop, the reagent has deteriorated and should be replaced.
Refer to para 2.6.2 for set up and operation of the Spectrophotometer.
Fill each of the two spectrophotometer sample cells(7, fig. 2-5) with 25 ml of sample water. Use the
graduated cylinder(31, fig. 1-1) to collect and measure the water.