First PrizeAuthor(s): George MartinSource: Sewage Works Journal, Vol. 12, No. 4 (Jul., 1940), pp. 803-804Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25029074 .

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Vol. 12, No. 4 GADGET CONTEST 803

GADGET CONTEST, CENTRAL STATES SEWAGE WORKS ASSOCIATION MEETING

IN OCTOBER, 1939

First Prize

By George Martin

Metropolitan Sewerage District, Green Bay, Wisconsin

The Determination of Hydrogen Sulfide in Sewage and

Polluted Water

In making routine determinations of hydrogen sulfide in sewage,

sewage gas, and polluted waters it was found that the procedure as de

scribed in Standard Methods was not satisfactory due to the fact that

polluted waters and sewage have an iodine demand. Therefore, a

modified or special method of procedure was adopted. This special method is based upon the known fact that filter paper treated with a

lead acetate solution will darken when placed in contact with hydrogen sulfide. It was found that by making a set of standards with which any sample might be compared consistent and fairly accurate results could

be obtained.

The apparatus necessary for making these determinations consists

of a standard 500 ml. filtering flask on the inside of which is placed an air diffuser made of a perforated aluminum tube connected to the flask's

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804 SEWAGE WORKS JOURNAL July, 1940

side tube by means of a rubber hose. On the outside of the side tube there is attached the rubber air intake hose. The lead acetate paper is held in place on the top of the suction flask between a rubber ring

"A," which is a standard Gooch crucible holder for an ordinary two

inch funnel, and a standard Gooch crucible holder "B,9 '

as is ordinarily used with a filter flask. "A" and "B" are held together by a utility clamp fastened to a ring stand. The rubber hose which is attached to the glass tubing of "B" is connected to a suction device.

In making a determination with this apparatus the sample to be tested is drawn into the flask directly from a pipette through the aera

tion tube. Air is then drawn through the liquid for two minutes and by so doing the hydrogen sulfide passes on up through the lead acetate

paper, discoloring it. The amount of hydrogen sulfide is determined by comparing the colored lead acetate paper with the standards and

converting the results into the desired units. In order to operate this apparatus satisfactorily it is necessary that

there be at least 100 ml. of liquid in the flask. Thus, if the sample being tested is high in hydrogen sulfide, it becomes necessary to dilute it with hydrogen sulfide free water. If it is desired to have the final results in p.p.m., this figure is arrived at by multiplying the color comparison in mg. by 1000 (mg. per liter or p.p.m.) and dividing by the ml. of sample used.

Example: Sample?10 ml.

Volume of water added to flask before sample?90 ml. Color comparison?0.05

0.05X1000 . p.p.m.-?-5 p.p.m.

The lead acetate paper is prepared by soaking filter paper in a 10

per cent solution of lead acetate and drying in an oven until approxi mately 10 to 15 per cent of the moisture remains in the paper. The

paper must then be kept in an air-tight container. Standards are made from a solution of hydrogen sulfide prepared

by generating hydrogen sulfide in distilled water from ferric sulfide by the addition of dilute sulfuric acid, the solution being standardized by iodine tit ration.

Gas may be analyzed for hydrogen sulfide by measuring a known

quantity in an Orsat gas measuring tube and then quickly passing the known volume through the above described apparatus. This method gives results in mg. per ml. used.

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