Alkalis Ik Colorado 
19 
in it had become so firm a mass by the time it reached the laboratory 
that one could not break it, with one’s fingers. No seedling plant 
could possibly have broken its way through such a mass. The sodic 
carbonate contained in this sample was 0.017 percent, or 680 pounds 
to the acre-foot. We do not, at the present time, know of any other 
cause why this soil becomes so hard. 
The reader probably recalls the statement previously made that 
sodic carbonate is one of the first products of the decomposition of 
rocks by the action of water. This is why the waters in our mountain 
streams all contain some sodic carbonate. He may further ask. Why, 
then, is not this salt everywhere? The answer is that it is practically 
everywhere in Colorado but not in injurious quantities, for the sim¬ 
ple reason that this salt, when it comes in contact with solutions of 
other salts in the soil, calcic or magnesic sulfate, for instance, it makes' 
a trade with them, exchanging its carbonate acid for their sulfuric 
acid, and the sodic carbonate becomes sodic sulfate and the calcic or 
magnesic sulfate becomes calcic or magnesic carbonate. In this man¬ 
ner the very poisonous sodic carbonate is transformed into the slight¬ 
ly poisonous sodic sulfate and at the same time forms calcic carbonate, 
which makes the sodic sulfate still less poisonous. There is usually 
a little sodic carbonate left; besides, there is a little being fomied all 
the time in the soil. The conditions are such in some places that the 
sodic carbonate is not changed and has already become so abundant, 
and is so nearly the only salt present, that it has become injurious, 
and there are great stores of it in the water beneath the land. The 
conditions in most parts of Colorado do not permit of the concentra¬ 
tion of this sodic carbonate, even where these mountain waters are 
used for irrigating.the land, for they are largely changed into the sul¬ 
fate and the small remnant is carried off in the drainage water, for the 
soil particles seem to have less power to hold this salt back than any 
other, unless it be the nitrate, which facts we infer from the readiness 
with which these two salts pass into drain-waters. So, if there be any 
drain-waters, they tend to wash it out of the soil. There are really 
two carbonates of soda which are not quite alike, the one is more 
poisonous than the other. The more poisonous one is our washing 
soda and the less poisonous one is our baking- soda. I have said noth¬ 
ing about the latter salt and will satisfy myself with the statement that 
the.one is more poisonous than the other. 
ORIGIN AND EFFECT OF THE NITRATES 
We have seen where the carbonates, one of our really trouble¬ 
some alkalis, come from, but we have not yet attempted to tell where 
the nitrates come from. Rocks, except near the surface, do not con¬ 
tain these salts, and when they occur in well- or river-water, except in 
