42 



THE SALTON SEA. 



in 100,000, equal to 12.36 parts expressed as C0 2 ; or to 8.43 parts of C0 3 when the car- 

 bonates in solution are expressed as the normal carbonates, which is considerably greater 

 than the value found for the C0 3 radicle in the evaporated residue. 



If the normal carbonates are formed on evaporating the water, then the combined 

 carbon dioxide in solution should be double that found in the evaporated residue. The 



i *? *%(\ 

 ratio found, however, is considerably greater than this, amounting to ' - = 2.9. It was 



shown by Davis 1 that, when magnesium carbonate is boiled with water, part of the carbon- 

 ate is hydrolyzed, forming a basic magnesium carbonate and magnesium hydroxide. The 

 same result undoubtedly takes place when water containing magnesium bicarbonate is 

 evaporated to dryness, which would explain the high ratio found between the carbon 

 dioxide in the water and in the evaporated residue. When the evaporations were carried 

 out in the same way, as was done each year by evaporating on a water bath in a platinum 

 dish, duplicate determinations of carbon dioxide in the residue agreed closely. It follows 

 from this that the same proportion of the magnesium carbonate must have been hydro- 

 lyzed in each determination. 



In the year 1909 it was noticed that, although the constituents as a whole increased 

 about 18 per cent since the previous analysis, the carbonate radicle as determined in the 

 evaporated residue, on the contrary, decreased. The quantity of calcium present increased 

 only 7 per cent over the preceding year instead of 18 per cent, as might have been expected. 

 The difference between these two values is more than equivalent to the deficiency found 

 for carbonates. This would, therefore, indicate that a precipitation of calcium carbonate 

 must have taken place during the years 1908 and 1909. 



A similar result has been found each year since then, so that the precipitation of cal- 

 cium carbonate would appear to be continuous. Table 11 gives the amounts by which 

 calcium and magnesium and the carbonate 

 radicle fall below the average increase in con- 

 centration for each year over the year pre- 

 ceding, and the last column shows the exact 

 values which the carbonate radicle in the 

 preceding column should have in order to be 

 exactly equivalent to the sum of the corre- 

 sponding values for Ca and Mg. This shows 

 that the amounts by which calcium and mag- 

 nesium each year fall below the average in- 

 crease in concentration of the constituents is approximately equivalent to the amount by 

 which the carbonate radicle falls below the same increase. 



In addition to determining the carbonate radicle an analysis was also made in 1911 

 of the free C0 3 in samples of water taken from the surface and the bottom of the lake. 

 The amounts found in the water from the two sources agreed within the limit of experi- 

 mental error, and gave as an average 0.72 part of C0 2 in 100,000 parts of water. 



On account of the small amount of phosphates in the water it would be very difficult 

 to make an analysis sufficiently accurate to show with certainty that they are undergoing 

 any change from year to year. It was for this reason that only a trace of phosphates 

 is reported in the analysis for 1911. 



Tests were also made for hydrogen sulphide by treating the water in a Nessler tube 

 with alkaline lead acetate, but a negative result was always obtained. 



It was not thought necessary to make a determination for barium, since its presence 

 would be precluded by the comparatively large amount of sulphates in solution. 



Table 11. — Showing amounts by u<hich calcium and mag- 

 nesium, and the carbonate radicle fall below the average 

 annual increase of the total constituents. 



1 Jour. Soc. Chem. Ind., 25, 788. 



