The Glass Stopper

At this point in time, the District of Columbia s attention shifted to trying to get some arsenic sampling around the Glenbrook Road property. To their surprise, the Corps agreed and not only did that lot but also the two adjoining ones. To their surprise, the arsenic was as high as 1000 ppm on the surface of the Glenbrook Road backyard and 600 ppm next door (the ERA had only found 241 ppm). Of course, this created quite a stir and at this point, the ERA was forced to take some of its own arsenic samples. 

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The reagent is conveniently stored as a solution in isopropyl alcohol. The molten (or solid) alkoxide is weighed out after distillation into a glass-stoppered bottle or flask and is dissolved in sufficient dry isopropyl alcohol to give a one molar solution. This solution may be kept without appreciable deterioration provided the glass stopper is sealed with paraffin wax or cellophane tape. Crystals of aluminium isopropoxide separate on standing, but these may be redissolved by warming the mixture to 65-70°. 

After sampling, remove the glass stopper and stem from the impinger flask. 

Procedure Preparation of 0.05A/ iodine. Dissolve 20 g of iodate-free potassium iodide in 30-40 mL. of water in a glass-stoppered 1 L graduated flask. Weigh out about 12.7 g of resublimed iodine on a watchglass on a rough balance (never on an analytical balance on account of the iodine vapour), and transfer it by means of a small dry funnel into the concentrated potassium iodide solution. Insert the glass stopper into the flask, and shake in the cold until all the iodine has dissolved. Allow the solution to acquire room temperature, and make up to the mark with distilled water. 

Ketene acetal is best stored in a bottle made of alkaline glass which is preferably new and dusted with sodium ter/.-but oxide (Note 7). The glass stopper should be very well greased. Even with these precautions a small amount of a voluminous precipitate of the white polymer will develop. 

Remove the glass stopper. Otherwise the funnel won t drain and you ll waste your time just standing there. 

Procedure Transfer 25 ml of 0.1 N bromine solution with the help of a pipette into a 500 ml iodine flask and dilute it with 120 ml of DW. Add to it 5 ml of hydrochloric acid, moisten the glass-stopper with water and insert the stopper in the flask. Shake the contents gently. Now, add 5 ml of potassium iodide solution, again lace the stopper and allow the resulting mixture to stand for 5 minutes in the dark. Titrate the liberated iodine with previously standardized 0.1 N sodium thiosulphate solution, adding 3 ml of freshly prepared starch solution towards the end-point. Each ml of 0.1N sodium thiosulphate is equivalent to 0.01598 g... 

Procedure Weigh accurately 0.5 g of phenol and dissolve in sufficient water to produce 500 ml in a volumetric flask. Mix 25.0 ml of this solution with 25.0 ml of 0.1 N potassium bromate in a 250 ml iodine flask and add to it 1 g of powdered KI and 10.0 ml of dilute hydrochloric acid. Moisten the glass stopper with a few drops of KI solution and place it in position. Set it aside in a dark place for 20 minutes while shaking the contents frequently in between. Add to it 10 ml of KI solution, shake the contents thoroughly and allow it to stand in the dark for a further duration of 5 minutes. Wash the stopper and neck of the flask carefully with DW, add 10 ml chloroform and titrate with the liberated iodine with 0.1 N sodium thiosulphate using freshly prepared starch as an indicator. Carry out a blank titration simultaneously and incorporate any necessary correction, if required. Each ml of 0.1 N potassium bromate is equivalent to 0.001569 g of C6H60. 

Remove the glass-stopper and pour the alcoholic extract through a small plug of purified glass wool in a small funnel and transfer the organic extract to a 1 cm absorption cell,... 

A 1-1. three-necked flask is fitted with a dry ice-acetone condenser, a glass stirrer, and a glass stopper (Note 1). Potassium amide is prepared in 400 ml. of liquid ammonia from 8.0 g. (0.20 g.-atom) of potassium metal (Note 2). The glass stopper is replaced with an addition funnel containing 32.1 g. (0.300 mole) (Note 3) of 2,(>-hitidine dissolved in about 20 ml. of anhydrous ether. The lutidine solution is added to the amide... 

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