18 MINERAL WATERS OF THE UNITED STATES. 



been conducted at the request of the Interior Department. As they 

 probabl} 7 did not reach a large number of chemists or physicians in 

 that form their republication in this connection seems advisable. 



HYDROGEN SULPHID. 



This determination was made by a method outlined in Button's 

 Volumetric Analysis, and is as follows: 



About 0.5 to 2 cc of tenth normal iodin is measured into a 500 cc flask 

 and the water under examination run in till the color of the iodin dis- 

 appears. Five' cubic centimeters of starch water is added and tenth 

 normal iodin run in till the blue color appears. The flask is then filled 

 to the mark with distilled water. The amount of water actually titrated 

 is found by subtracting the sum of iodin, starch solution, and distilled 

 water from 500 cc. As an excess of iodin solution is required to pro- 

 duce the blue color, a correction is applied by making 5 cc of starch 

 solution up to 500 cc with distilled water and adding tenth normal 

 iodin until the color of the solution is just as blue as that in the actual 

 determination. This figure subtracted from the first figure gives the 

 number of cubic centimeters of tenth normal iodin used by the hydro- 

 gen sulphid. 



CARBON DIOXID (iN EXCESS OF THAT NECESSARY TO FORM NORMAL CARBONATES). 



The determination of the carbon dioxid existing in water in excess 

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

 Button's Volumetric Analysis and designed by Pettenkofer. One hun- 

 dred cubic centimeters of the water are treated in a flask with 3 cc of 

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

 ammonium chlorid, and 45 cc of a saturated solution of calcium hydroxid 

 whose strength has previously been determined in terms of tenth nor- 

 mal hydrochloric acid, using lacmoid as indicator. The flask is stop- 

 pered, 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 are drawn off in a pipette and titrated 

 with tenth normal hydrochloric acid, using lacmoid as indicator. This 

 result is multiplied by three and subtracted from the amount of tenth 

 normal hydrochloric acid necessary to neutralize 45 cc of the cal- 

 cium hydroxid solution, thus giving the amount of calcium hydroxid 

 solution acted upon by the carbon dioxid in terms of tenth normal 

 acid. Multiplying the number of cubic centimeters so found by 0.0022, 

 the weight of carbon dioxid in 100 cc above that necessary to form 

 normal carbonates is found. Dividing the weight so found by the 

 weight of 1 cc of carbon dioxid at C. and 760 mm pressure and multi- 

 plying the result by 10, the number of cubic centimeters of carbon 

 dioxid in a liter in excess of that necessary to form normal carbonates 

 is obtained. The figure is then corrected to correspond to 1,000 grams 

 of the water. 



