Kr eider — Oxygen in Air and in Aqueous Solution. 363 



carbon dioxide liberated forces the liquid from the bulb into a 

 beaker which contains bicarbonate in amount sufficient, as pre- 

 viously determined, to neutralize all the acid taken. When 

 tbe exit is too slow more bicarbonate may be admitted through 

 the other stop-cock, and after neutralization has been com- 

 pleted the bulb may be washed out without any danger from 

 the admission of air. 



All the water employed, both for the solution of potassium 

 iodide and for the various connections, was free of oxygen. 

 It was prepared by filling a three liter flask with distilled water 

 and boiling until the volume of the liquid was reduced about 

 one-third, when the flask was closed by a doubly perforated 

 rubber stopper and fltted as a wash bottle. By means of the 

 tube which reached below the surface of the water, pure car- 

 bon dioxide was passed through while the water was still boil- 

 ing, whicli together with the escaping steam was sure to expel 

 all oxygen. Then the heat was removed and the current of 

 carbon dioxide continued until the boiling ceased, when the 

 escape tube was closed by a piece of rubber tubing and screw 

 pinch-cock. As the water cooled it was well shaken while still 

 in connection with the carbon dioxide generator, and thus 

 became saturated with the gas, which was then pumped in under 

 considerable pressure by the little hand pump described in a 

 previous paper from this laboratory. By this means the water 

 could be drawn as needed without the introduction of any air. 

 The escape tube was provided with a rubber tube and screw 

 pinch-cock, and a long, slender nozzle which could be inserted 

 into the tubes of the absorption apparatus. A bottle thus 

 charged sufficed for all the determinations and required only an 

 occasional supply of carbon dioxide when large draughts of 

 water were required for making the potassium iodide solution. 



The potassium iodide solution was made up to contain one 

 gram of the salt in thirty cubic centimeters of water, and was 

 contained in convenient form in an ordinary wide-mouthed 

 bottle fltted as a wash bottle, and graduated approximately for 

 each thirty cubic centimeter's volume — the amount usually 

 taken. The potassium iodide was weighed into the bottle, 

 which was then closed and all air expelled by a current of car- 

 bon dioxide, when the desired amount of water, free of oxygen, 

 was drawn in, and attachment again made with the carbon 

 dioxide generator. After allowing the gas to pass for several 

 minutes the exit was closed and the gas pumped in by the lit- 

 tle hand pump. Inasmuch as this solution, when it was used, 

 was drawn into an exhausted bulb, the bottle could be emptied 

 without ever exposing its contents to the air. 



Am. Jour. Sci. — Fourth Series, Vol. II, No. 11. — November, 1896, 

 26 



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