. The analysis of food and drugs . unlimitedquantity of the iodide: 2HI+0 = H20+l2. This reaction is the one utilized by Dr. Thresh in theprocess he has devised for estimating the oxygen dissolvedin water. The process is described by him {Journ. , vol. Ivii., p. 185) as follows : The following are the reagents required : (1) Solution of sodium nitrite and potassium iodide. Sodium nitrite 05 gramme. Potassium iodide 200 grammes. Distilled water 100 (2) Dilute sulphuric acid. Pure sulphuric acid 1 part. Distilled water 3 parts. (3) A clear, fresh solution of starch. (4) A standard s
. The analysis of food and drugs . unlimitedquantity of the iodide: 2HI+0 = H20+l2. This reaction is the one utilized by Dr. Thresh in theprocess he has devised for estimating the oxygen dissolvedin water. The process is described by him {Journ. , vol. Ivii., p. 185) as follows : The following are the reagents required : (1) Solution of sodium nitrite and potassium iodide. Sodium nitrite 05 gramme. Potassium iodide 200 grammes. Distilled water 100 (2) Dilute sulphuric acid. Pure sulphuric acid 1 part. Distilled water 3 parts. (3) A clear, fresh solution of starch. (4) A standard solution of sodium thiosulphate. Pure thiostilphate 7-75 grammes. DistUled water 1 litre. (1 corresponds to 025 milligramme of oxygen.) 94 CHEMICAL AND BIOLOGICAL ANALYSIS OF WATER The apparatus required is very simple, and consists of awide-mouthed white glass bottle of about 500 capacity,closed with a caoutchouc stopper having four one passes a tube, drawn out at its lower extremity A ^4 Jf!>iai#. Theeshs Appaeatus. to a rather fine point, and connected at the upper end, bymeans of a few inches of rubber tubing, with the burettecontaining the thiosulphate. Through another openingpasses the nozzle of a separatory tube, having a stopperand stopcock. The capacity of this tube, when full to the CHEMICAL EXAMINATION 95 stopper, must be accurately determined. Through thethird opening passes a tube, which can be attached to theordinary gas supply. Through the last aperture is passedanother tube for the gas exit, and to this is attached asufficient length of rubber tubing to enable the cork at itsend to be placed in the neck of the separator when thestopper is removed. A small piece of glass tube projectsthrough the cork, to allow of the escaping gas beingignited. The apparatus is used in the following manner: Thebottle A being cleaned and dry, the perforated bung is in-serted, the burette charged, and the tube fixed in its tube E is con
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