Sulfur test barium chloride method – LaMotte DCL-20 Colorimeter User Manual
Page 27
SULFUR TEST
BARIUM CHLORIDE METHOD
QUANTITY
CONTENTS
CODE
60 mL
*Sulfate Extracting Solution
*6363-H
10 g
*Sulfate Reagent
*V-6277-D
1
Pipet, 1 mL, plastic
0354
1
Spoon, 1.0g
0697
1
Spoon, 0.1 g
0699
*WARNING: Reagents marked with a * are considered hazardous substances. Material Safety Data Sheets (MSDS) are
supplied for these reagents. For your safety, read label and accompanying MSDS before using.
Sulfur is essential to the formation of protein and affects various aspects of plant metabolism. Sulfur-deficient plants are
pale green in color with thin, reedy stems. Negatively charged sulfate ions are easily leached. The major sources of soil
sulfate are fertilizer containing sulfate compounds and atmospheric sulfur dioxide carried into the soil by precipitation.
RANGE:
0-172 ppm
METHOD:
Sul fate ion is pre cip i tated in an acid me dium with bar ium chlo ride to form bar ium sul fate crys tals
in pro por tion to the amount of sul fate pres ent.
IN TER FER ENCE:
Sus pended mat ter and color in ter fer ence may be re moved by a fil tra tion step. Sil ica in ex cess of
500 mg/L will in ter fere.
PROCEDURE
1. Use the 1 mL pipet (0354) to add 1 mL of *Sulfate Extracting Solution (6363) to the graduated vial (0989) then add
deionized water to the graduation.
2. Add 3 one gram measures of soil using the 1 g spoon (0697). Cap vial and shake for five minutes.
3. Filter and collect all of the soil filtrate using the funnel (0459) and filter paper (0463). If the filtrate is not clear, filter a
second time.
4. Fill a clean colorimeter tube (0967) to the 10 mL line with the soil filtrate.
5. Select setting 1 on the “Select Wavelength” knob.
6. Insert tube containing sample into chamber and press the “30 Second Read” button. Adjust “100"%T with the ”Set
Blank" knob.
7. Remove the tube from the chamber. Use the 0.1 g spoon (0699) to add one level measure of *Sulfate Reagent (6277)
to the sample tube. Cap the tube and shake until powder has dissolved. A white precipitate will develop if sulfates are
present.
8. Allow the reaction to proceed for 5 minutes, then mix again before inserting tube into chamber of colorimeter. Cover
and measure %T as soon as reading stabilizes.
9. Consult chart to find the concentration in parts per million (ppm) of sulfur.
NOTE:
A white film is de pos ited on the in side of test tubes as a re sult of the sul fate test. Thor oughly clean and rinse
test tubes af ter each test.
SULFUR CALIBRATION CHART (ppm)
%T
9
8
7
6
5
4
3
2
1
0
90
6.7
7.2
7.6
8.1
8.5
9.0
9.4
9.9
10.3
10.8
80
11.2
11.7
12.2
12.6
13.1
13.6
14.0
14.5
15.0
15.5
70
16.0
16.5
17.0
17.5
18.0
18.5
19.1
19.6
20.1
20.7
60
21.2
21.8
22.3
22.9
23.5
24.1
24.6
25.3
25.9
26.5
50
27.1
27.8
28.5
29.1
29.8
30.5
31.3
32.0
32.8
33.5
40
34.4
35.2
36.0
36.9
37.8
38.8
39.7
40.7
41.8
42.9
30
44.0
45.2
46.4
47.7
49.1
50.5
52.0
53.6
55.2
57.0
20
58.9
60.9
63.0
65.3
67.8
70.4
73.3
76.4
79.8
83.5
10
87.6
92.0
97.0
102.6
108.8
115.9
124.0
133.3
144.1
156.9
0
172.1
27
1985-01 • 10/01