The Composition of Sewer Air
285
Direct calibrations of these procedures were made using air streams polluted artificially
at various concentration levels corresponding to the levels found in sewer air. These
precisely known levels were achieved by a technique of controlled membrane permeation,
specially developed so as to be capable of checking directly by gravimetry. Where
applicable for example for GLC work appropriate microgram or microlitre quantities of
pure chemicals could be used both for identifications and quantitative measurements.
Details of all procedures will be published in a later paper, but the following notes
provide further information on the identity of the particular analytical methods used.
The procedures of Table 2 are taken in turn.
The Draeger tubes referred to are those prepared by Draeger Werk of Lübeck,
Germany. Tubes for C0 2 testing were verified by absorbing parallel samples in barium
hydroxide solution, and tubes for H 2 S and Mercaptan were checked in the laboratory
using known concentrations of H 2 S and EtSH. H 2 S was determined using the reaction
with NN-dimethyl paraphenylene diamine followed the standard Pomeroy procedure in
general but with strict attention to timing of reagent additions and colour measurement.
The reference curves were thoroughly checked, both directly by absorption of known
amounts of 99% pure gaseous H 2 S into alkaline cadmium acetate-hydroxide as for the
field test procedure and also using the standard iodometric technique as a parallel
reference procedure.
Absorption techniques were thoroughly checked to also ensure satisfactory efficiency
both for the absorption and for test reactions or regeneration procedures. The retention
of H 2 S by ZnCl 2 so as to allow separate absorption of sulphides on HgCl 2 discs was
verified by careful checking. The Zitomer-Dahlgren (1964) Colorimetric estimation of
alkylamines is based on a chlorine-NH 2 reaction, and the method of Sawicki et al (1961)
for aldehydes is based on a simple condensation with 3—methyl 2— benzothiazolone
hydrazonium hydrochloride and colour formation using FeCl 3 reagent.
The use of impregnated fibre glass discs generally followed the prescriptions of Adams,
Bamesberger and Robertson (1968), Okita (1970) and Feldstein, Balestrieri and Levaggi
(1965). When concentrated H 2 S0 4 is used for sewer air sampling, moisture uptake leads
to partial blockage and protracted sampling periods, but these techniques generally
proved excellent. Activated carbon absorption is very simple to apply.
Summary of Analytical Data:
The Analytical data are summarised in Table 4.
285
Direct calibrations of these procedures were made using air streams polluted artificially
at various concentration levels corresponding to the levels found in sewer air. These
precisely known levels were achieved by a technique of controlled membrane permeation,
specially developed so as to be capable of checking directly by gravimetry. Where
applicable for example for GLC work appropriate microgram or microlitre quantities of
pure chemicals could be used both for identifications and quantitative measurements.
Details of all procedures will be published in a later paper, but the following notes
provide further information on the identity of the particular analytical methods used.
The procedures of Table 2 are taken in turn.
The Draeger tubes referred to are those prepared by Draeger Werk of Lübeck,
Germany. Tubes for C0 2 testing were verified by absorbing parallel samples in barium
hydroxide solution, and tubes for H 2 S and Mercaptan were checked in the laboratory
using known concentrations of H 2 S and EtSH. H 2 S was determined using the reaction
with NN-dimethyl paraphenylene diamine followed the standard Pomeroy procedure in
general but with strict attention to timing of reagent additions and colour measurement.
The reference curves were thoroughly checked, both directly by absorption of known
amounts of 99% pure gaseous H 2 S into alkaline cadmium acetate-hydroxide as for the
field test procedure and also using the standard iodometric technique as a parallel
reference procedure.
Absorption techniques were thoroughly checked to also ensure satisfactory efficiency
both for the absorption and for test reactions or regeneration procedures. The retention
of H 2 S by ZnCl 2 so as to allow separate absorption of sulphides on HgCl 2 discs was
verified by careful checking. The Zitomer-Dahlgren (1964) Colorimetric estimation of
alkylamines is based on a chlorine-NH 2 reaction, and the method of Sawicki et al (1961)
for aldehydes is based on a simple condensation with 3—methyl 2— benzothiazolone
hydrazonium hydrochloride and colour formation using FeCl 3 reagent.
The use of impregnated fibre glass discs generally followed the prescriptions of Adams,
Bamesberger and Robertson (1968), Okita (1970) and Feldstein, Balestrieri and Levaggi
(1965). When concentrated H 2 S0 4 is used for sewer air sampling, moisture uptake leads
to partial blockage and protracted sampling periods, but these techniques generally
proved excellent. Activated carbon absorption is very simple to apply.
Summary of Analytical Data:
The Analytical data are summarised in Table 4.