tained but 1-100.000 of its weight of sulphuric acid, a drop of a
concentrated solution of Nitrate of Baryta still produced a precipi-
tate of sulphate of Baryta, which by heating quickly settled to the
bottom in the form of plainly visible white grains, insoluble in acids,
and not altered, at all by the presence of organic matter, or such
others as may be extracted from the soil by acids.

We also know by analyses of Boussingault and of Fresenius,
that a potato crop of 10 tons contains

Tuber 10 tons, containing of Sulph. Acid, 30 lbs.
Top 2 " " "          " " 10 lbs.

Total amount of Sulphuric Acid 40

If we now take a crop of 10 tons as an average crop per acre,
then it is necessary that the soil contains at least 40 lbs. of sulphuric
acid (equal to one bushel of plaster of Paris,) if it shall be able to
produce the above crop.

We have further to remember that the average weight of one
acre of soil, one foot deep, is 3000 tons—6,000,000 lbs.

6,000,000 lbs. of soil ought therefore to contain 40 lbs. of sul-
phuric acid to produce the average crop of potato, and consequently
every part of this mass 1-150.000 of its weight of sulphuric acid.

Or if we dissolve the sulphuric acid in a certain quantity of the
above mass, by a solvent of equal weight, the solution obtained
will also contain 1-150,000 of sulphuric acid; or by evaporating
from it one-third, a solution will be obtained which contains 1-1900-
000 of sulphuric acid, an amount which can be detected by Nitrate
of Baryta, as above stated.

For the purpose of testing a soil for its sufficiency or deficiency
in sulphuric acid, it is therefore only necessary to take a certain
portion of the prepared solution of the soil to evaporate from it
one-third, and then to test with Nitrate of Baryta. If no precipi-
tate occurs after heating the liquid, it is a proof that the soil is
deficient in sulphuric acid.

Determination of Chlorine.

For the detection of chlorides, we are also favored with are-agent
which distinguishes itself by its sensibility. Experiments which
were made to try its sensibility, have resulted in the observation
that in a solution of Chloride of Sodium which contained but
1-100.000 of its weight of Chlorine, a drop of a concentrated solu-
tion of nitrate of silver, still produced a precipitate of chloride of
silver, which by heating and stirring quickly settled to the bottom
in the form of plainly visible white flakes, which after some time
when exposed to the light, became blackened; they are easily
soluble in ammonia, but not in nitric acid. It could not be found

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