BUCHI Scrubber K-415 - Manual (Page 37)

5 Putting into operation
37 K-415 Operation Manual, Version B
5 .9 .1 Washing solutions for acidic vapors and gases
• Sodium hydroxide 8-10 %, max. 20 %
• Sodium carbonate
– dissolve 600 g Na
2
CO
3
in 3 L distilled warm water, or
– dissolve 1.7 kg Na
2
CO
3
· 10 H
2
O in 3 L distilled warm water
Color indicator
A color indicator is added to the washing solution to assess its washing power visually as well.
We recommend to use a spatula tip of color indicator for 3 L of washing solution.
Bromothymol blue serves as a stan dard indicator. The transition area here is between pH 6.0 to 7.6.
Thus the fresh solution has a blue color while the neutralized or acidic solution has an orange yellowish
color.
Depending on the application purpose, other suitable color indicators should be used.
5 .9 .2 Washing solutions for alkaline vapors and gases
• Hydrochloric acid, max. 15 %
• Sulphuric acid, max. 20 %
Depending on the area of application, it is recommended to use different washing solutions or concen-
trations. The Scrubber K-415 is supplied ex works with a base-resistant lip gasket.
NOTE
For operating with acid washing solutions, an acid-resistant lip gasket should be used.
Color indicators
Table 5-1: Indicators for washing solutions for alkaline vapors and gases
Name Transition pH range Color change
Bromocresol green 3.8 - 5.4 yellow to blue
Bromothymol blue 5.8 - 7.6 yellow to blue
Methylen red 4.4 - 6.2 yellow to red