16 HOT SPRINGS, ARKANSAS. 



After being .shaken with this solution for about four minutes the gas 

 was passed back into the burette, the burette allowed to stand for a 

 few minutes, and the reading taken. The last reading gave the num- 

 ber of cc of nitrogen present, and the difference between the first and 

 last reading, the number of cc of oxygen. A temperature and baro- 

 metric pressure reading were also taken, to correct the gas volume to 

 0° C and 760 mm. pressure. Numerous precautions as to temperature, 

 saturation of reagents, etc., not mentioned in the above brief sketch 

 were taken, all of which can be found in any standard work on gas 

 analysis. 



Carbon dioxide. — (In excess of that necessary to form normal car- 

 bonates.) The determination of the carbon dioxide existing in water 

 in excess of that present as normal carbonates was made by a method 

 given in Sutton's Volumetric Analysis and designed by Pettenkof er. 

 One hundred cc of the water was treated in a flask with 3 cc of a 

 saturated solution of calcium chloride, 2 cc of a saturated solution of 

 ammonium chloride, and 15 cc of a saturated solution of calcium 

 hydroxide, whose strength had previously been determined in terms of 



tt; hydrochloric acid, using lacmoid as indicator. The flask was 



stoppered, the solution well mixed, and the whole set aside for twelve 

 hours to allow the calcium carbonate to settle. At the end of this 

 time 50 cc of the clear solution was drawn off in a pipette and titrated 



with wt: hydrochloric acid, using lacmoid as indicator. This result 

 was multiplied by three and subtracted from the amount of tt. hydro- 

 chloric acid necessary to neutralize 15 cc of the calcium hydroxide 

 solution, thus giving the amount of calcium hydroxide solution that had 



n 

 been acted on by the carbon dioxide in terms of ^ acid. Multiply- 

 ing the number of cc so found by 0.0022, the weight of carbon dioxide 

 in 100 cc above that necessary to form normal carbonates was found. 

 Dividing the weight so found by the weight of 1 cc of carbon dioxide 

 at 0° C and 760 mm. pressure and multiplying the result by 10, the 

 number of cc of carbon dioxide in a liter in excess of that necessary 

 to form normal carbonates was given. 



Carbon dioxide. — (Given off from the bicarbonates when they are 

 evaporated to dryness.) In making this determination the method of 

 Cameron a for the "Estimation of carbonates and bicarbonates in 

 aqueous solution" was used. By this method the amount of bicarbonic 

 acid ion (HC0 3 ) was determined, and from this we could easily estimate 

 how much of the bicarbonic acid would remain as the normal carbon- 

 ate and how much be given off as carbon dioxide. The method is as 

 follows: 



To one hundred cc of the water was first added a few drops of 

 phenolphthalein. In case there were alkali carbonates present the 

 usual red color would be evident. The solution was now titrated with 

 a solution of HKS0 4 , containing 6.758 grams to the liter, adding the 

 HKS0 4 solution at the rate of a drop every two or three seconds, 

 until the red color had completely disappeared. The reading on the 



a Report 64 U. S. Department of Agriculture; American Chemical Journal. 23,471 

 (1900). 



