Carbonyl sulfide COS NO.21LA
21LA


Performance

Measuring Range

2 to 5 ppm

5 to 50 ppm

50 to 125 ppm

Number of Pump Strokes

2

1

1/2

Correction Factor

0.4

1

2.5

Sampling Time

3 minutes per pump stroke

Detecting Limit

0.8 ppm (n=2)

Color Change

Bluish Purple White

Reaction Formula

COS is oxidezed by iodine pentoxide and sulfuric acid
to generate SO2 in primary tube. The SO2 reacts with iodine
to breach the reagent to white by iodine-starch reaction.
COS + I2O5 + H2SO4 SO2 + CO2
SO2 + I2 + H2O 2HI + H2SO4
Coefficient of Variation 10% (for 5 to 20 ppm), 5% (for 20 to 50 ppm)
Shelf Life 2 Years
Corrections for
temperature & humidity		 Temperature correction is necessary
Store the tubes in the refrigerator to keep at 10oC (50oF) or below.


Possible coexisting substances and their interferences (NOTE)

Substance

Concentration

Interference

Change color by itself

Carbon monoxide

500 ppm

Discolors to black

Discolors to black at 500 ppm

Sulfur dioxide
Carbon disulfide

 -

Plus error

Discolor to white

Carbon dioxide

 -

No effect

No discoloration

Nitrogen dioxide

2 ppm

Plus error

Discolors to brown at 2 ppm

Hydrogen sulfide

1000 ppm

No effect
at 1pump stroke

 *

Propane,Butane

10%

No effect

Produce black stain
at the top of the discolored area.
*In case the primary tube is totally discolors, analyzer tube will give white discoloration by hydrogen sulfide.


Calibration gas generation High pressure gas cylinder method


TLV-TWA TLV-STEL Explosive range
- - 12 to 19%

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