HOT SPRINGS, ARKANSAS. 13 



and part of the magnesium and carbonic acid ions unite to form mag- 

 nesium carbonate, as follows: 



so that we have in solution not only the calcium carbonate, magnesium 

 sulphate, and magnesium, calcium, carbonic acid, and sulphuric acid 

 ions with which we started, but also some calcium sulphate and mag- 

 nesium carbonate. 



In calculating the above-mentioned hypothetical combination, sodium 

 is joined to the nitrous and nitric acid ions; potassium to iodine and 

 bromine; calcium to the phosphoric-acid ion and sodium to the metaboric- 

 acid ion. Chlorine is assigned to the bases in the order NH 4 , Li, K, 

 Na; sulphuric-acid ion in the order NH 4 , Li, K, Na, Mg, Ca, and the 

 residual bases are joined to bicarbonic-acid ion in the order Na, Mg, 

 Ca, Mil, Fe. In case the bicarbonic-acid ion is not present in large 

 enough amounts to join with all the remaining bases, the residual cal- 

 cium is joined to silica to form calcium silicate, and manganese and iron 

 are calculated as Mn 3 4 and Fe 2 3 , respectively. 



METHODS OF EXAMINATION. 



Temperature. — The temperature of each spring was taken with an 

 accurately standardized maximum thermometer on the date of the 

 sanitaiy analysis of the water. Finally^ the temperatures of all of the 

 springs were taken in one day. It will be noticed that these tempera- 

 tures sometimes vary quite a few degrees for the same spring. This 

 seems to be due to two causes. In the first place the temperature of 

 the spring as it issues from the earth varies slightly from time to time; 

 secondly, the springs sometimes have quite large basins, so that we can 

 not get the temperature just as the water issues from the earth, but 

 must take it as influenced by a comparatively large body of water, 

 which in turn has been cooled to some extent by standing in the air. 

 When these springs have recently been drained the temperature is 

 nearly the same as where they issue from the earth, but when the basin 

 is full the temperature is quite a few degrees lower. 



Flow. — The flow of each spring was measured by observing the 

 length of time taken to fill a vessel of known capacity from a pipe that 

 drained the spring in question. In some cases such determinations 

 could not be made, so the flow of the springs was estimated by com- 

 paring them with other springs of known flow. Such estimations 

 were made by the head waterman of the reservation, Mr. Ed Hardin, 

 who by long experience had arrived at such a point that he could come 

 very near the correct figure. 



Hydrogen sulphide.- — The test for the presence of hydrogen sul- 

 phide was made both by boiling a sample of water and noticing the 

 smell, and by passing the vapors over a piece of lead acetate paper. 

 In a few cases, as a check, an actual determination of the hydrogen 

 sulphide by the method given in Sutton's Volumetric Analysis was 

 made. This is as follows: 



About 0.5 c. c. of jt: iodine was measured into a 500 c. c. flask and 

 the water under examination run in till the color of the iodine disap- 

 peared. Five c. c. of starch water was added and -tt. iodine run in till 

 the blue color appeared. The flask was then filled to the mark with 



