40 
Colorado Experiment Station 
water similar in composition to that of our other mountain streams, 
fairly represented by the waters of the Rio Grande which we will use 
for comparison. 
ANALYSES OF RESIDUES FROM SAN LUIS LAKE WATER 
Sample taken 
Sample taken 
15 Oct. 1902 
8 May, 1916 
Percent 
Percent 
Silicic acid . 
9.118 
13.401 
Sulfuric acid. 
5.801 
10.255 
Phosphoric acid . 
0.116 
Carbonic acid . 
22.096 
16.813 
Chlorin. 
4.209 
5.146 
Calcic oxid . 
2.673 
4.178 
Magnesic oxid . 
5.613 
4.632 
Potassic oxid . 
13.832 
8.559 
Sodic oxid . 
35.590 
28.210 
Aluminic oxid ) 
0.629 
0.856 
Ferric oxid i 
0.301 
Manganic oxid. 
0.216 
0.465 
Ignition . 
1.574 
(6.350) 
Sum . 
101.351 
101.162 
Oxygen equivalent to 
chlorin . 
.948 
1.162 
* 
Total . 
100.413 
100.000 
Total solids in grains 
per imp. gal. 
62.2 
55.9 
Loss on ignition in 
grains per imp. gal 
8.2 
Sanitary Analyses of the Waters 
Total solids . 
Chlorin . 
Nitrogen as nitrates. 
Nitrogen as nitrites.. 
Saline ammonia . 
Aluminoidal ammonia 
Oxygen consumed . . . 
Parts per Million 
_ 888.5900 
_ 36.1420 
. Trace ' 
_ 1.4000 
. ... 0.6250 
_ 0.7130 
- 31.5000* 
Parts per Million 
798.0000 
39.0000 
0.1500 
0.0100 
0.3300 
1.0700 
14.1000 
*The oxygen consumed was reduced to 10 p.p.m. by treament with* calcic 
hydrate. 
These samples were taken at different seasons of the year and 
nearly 14 years apart. I personally took both samples and remember 
distinctly that the lake was very low when the first of these was taken 
and, though I have seen this lake very often, I do not remember ever 
to have seen it so high as when the last sample was taken; therefore, 
it is probable, that these results represent the extreme differences to 
be met with in samples of this water. The results are remarkable, 
for, as I understand it, the drain ditches have been tailing their water 
into the trough of the valley for three or four years, and, as stated, 
the country for about two miles to the west of the lake was, at the 
