Potassium chlorid 26.8 “ “
Magnesium “ 34.2 “ “
Water 39.0 “ “
The commercial article as taken from the mines, as is seen above, has
less potash (K₂O) than kainit, the mean content being about nine and
nine-tenths per cent. Those proposing to use this body for fertilizing
purposes should bear in mind that it contains less potash and more
chlorin than kainit.
Carnallit occurs in characteristic brown-red masses. On account of its
highly hygroscopic nature it should be kept as much as possible out
of contact with moist air and should not be ground until immediately
before using.
By reason of the greater bulk in proportion to its content of potash
and its hygroscopic nature and consequent increased difficulty in
handling, the price per unit of potash in carnallit is less than in
kainit.
In some localities small quantities of ammonium chlorid have been found
with carnallit but not to exceed one-tenth per cent. It has therefore
no practical significance to the farmer but may be of interest to the
analyst.
=239. Polyhalit.=—Polyhalit is a mineral occurring in Stassfurt
deposits and consisting of a mixture of potassium, magnesium, and
calcium sulfates, with a small proportion of crystal water. This
mineral, on account of its being practically free of chlorin, would
be one especially desirable for use in those cases, as in the culture
of tobacco, where chlorids are injurious. Unfortunately, it does not
occur in sufficient quantities to warrant the expectation of its
ever being found in masses large enough to become a general article
of commerce. It is found only in pockets or seams among the other
Stassfurt deposits, and there is no assurance given on finding one of
these deposits of polyhalit that it will extend to any great distance.
The composition of the mineral is shown by the following formula:
K₂SO₄·MgSO₄·(CaSO₄)₂·H₂O. Its percentage composition is shown by the
following numbers:
Potassium sulfate 28.90 per cent.
Magnesium sulfate 19.93 “ “
Calcium sulfate 45.18 “ “
Water 5.99 “ “
The percentage of potash corresponding to the above formula is 15.62.
It therefore contains a considerable excess of potash over kainit, and
on account of its freedom from chlorids, would be preferred for many
purposes.
=240. Krugit.=—This mineral occurs associated with polyhalit and
differs from it only in containing four molecules of calcium sulfate
instead of two. Its formula is: K₂SO₄·MgSO₄·(CaSO₄)₄·H₂O. As it comes
from the mines it is frequently mixed with a little common salt. Its
mean percentage composition as it comes from the mines is given in the
following numbers:
Potassium sulfate 18.60 per cent.
Magnesium sulfate 14.70 “ “
Calcium sulfate 61.00 “ “
Sodium chlorid 1.50 “ “
Water 4.20 “ “
The percentage of potash corresponding to the above formula is 10.05.
It is therefore less valuable than kainit in so far as its content of
potash is concerned. This salt also exists in limited quantities and is
not likely to become an important article of commerce.
=241. Sylvin.=—One of the alteration products of carnallit is a
practically pure potassium chlorid which, as it occurs in the Stassfurt
mines is known as sylvin. The alteration of the carnallit arises from
its solution in water from which, on subsequent evaporation, the
potassium chlorid is deposited alone. This mineral is found in only
limited quantities in the Stassfurt deposits and it therefore does not
have any great commercial importance.
=242. Sylvinit.=—This mineral has been mined in recent years in
considerable quantities. It is, in fact, only common salt carrying
large quantities of potassium chlorid together with certain other
accidental impurities. It was probably formed by the drying up of a
saline mass in such a way as not to permit the complete separation of
its mineral constituents. The average composition of sylvinit as it
comes from the mines is given in the following table:
Potassium chlorid 30.55 per cent.
Sodium chlorid 46.05 “
Potassium sulfate 6.95 “
Magnesium sulfate 4.80 “
Magnesium chlorid 2.54 “
Calcium sulfate 1.80 “
Water and insoluble 7.29 “
This salt is richer in chlorin than any other of the Stassfurt potash
minerals, containing altogether 79.14 per cent of chlorids. Its potash
content amounts to 23.04 per cent, but in proportion to the potash
which it contains, it is relatively poorer in chlorin than kainit and
carnallit. On account of its high content of potash the freights on a
given weight thereof as contained in sylvanit are lower than for kainit
and carnallit.
=243. Kieserit.=—The mineral kieserit is essentially magnesium sulfate
and it does not necessarily contain any potash salts. Under the name
of kieserit, however, or bergkieserit, there is mined a mixture of
carnallit and kieserit, which is a commercial source of potash. The
mixture contains the following average content of the bodies named:
Potassium chlorid 11.80 per cent.
Magnesium sulfate 21.50 “
Magnesium chlorid 17.20 “
Sodium chlorid 26.70 “
Calcium sulfate 0.80 “
Water 20.70 “
Insoluble 1.30 “
This mixture contains only about seven per cent of potash and would
not prove profitable when used at a distance from the mines on account
of the cost of freights. It has proved valuable, however, for a top
dressing for meadow lands in the vicinity of Stassfurt.
=244. Schönit.=—Among the Stassfurt deposits there occurs in small
quantities a mineral, schönit, which is composed of the sulfates
of potassium and magnesium. The quantity of the mineral occurring
naturally is very small and therefore it has no commercial importance.
When, however, kainit is washed with water the common salt and
magnesium chlorid which it contains being more soluble are the first
leached out, and the residue has approximately the composition of the
pure mineral. This mixture, as prepared in the way mentioned above, has
the following average composition:
Potassium sulfate 50.40 per cent.
Magnesium sulfate 34.00 “
Sodium chlorid 2.50 “
Water 11.60 “
The percentage of potash corresponding to the above composition is
27.2. This substance being so rich in potash, and practically free
of chlorids, is well suited to transportation to great distances and
for general use in the field. Since, however, a considerable expense
attends the manufacture of the artificial schönit, the advantages above
named give it very little, if any, advantage in competition with the
other potash salts as they come from the mines. It has, however, an
especial value for the fertilization of tobacco and vineyards.
=245. Potassium Sulfate.=—Several grades of potassium sulfate are
found in the market for fertilizing purposes, some of them quite
pure, containing over ninety-seven per cent of the pure sulfate. The
following data show the composition of a high grade and low grade
potassium sulfate of commerce:
High grade. Low grade.
Potassium sulfate 97.20 per cent. 90.60 per cent.
Potassium chlorid 0.30 “ 1.60 “
Magnesium sulfate 0.70 “ 2.70 “
Magnesium chlorid 0.40 “ 1.00 “
Sodium chlorid 0.20 “ 1.20 “
Insoluble 0.20 “ 0.30 “
Water 0.70 “ 2.20 “
Naturally, high grade sulfates of this kind can only be prepared in
chemical factories built especially for the work. The result is that
the potash per unit is raised greatly in price. When, however, the
fertilizers are to be transported to a great distance, the saving in
freight often more than compensates for the higher price of the potash.
It therefore happens that there are many places in this country where
the actual price of potash per pound is less in high grade sulfates
than in kainit or carnallit. When, in addition to this, the especial
fitness of the high grade sulfates for certain forms of fertilization,
especially tobacco growing, is considered, it is seen that at this
distance from the mines these high grade salts are of no inconsiderable
importance. The percentage of potash in the high grade sulfates often
exceeds fifty.
=246. Potassium Magnesium Carbonate.=—This salt has lately been
manufactured and used to a considerable extent, especially for tobacco
fertilizing. As furnished to the trade it has the following average
composition:
Potassium carbonate 35 to 40 per cent.
Magnesium carbonate 33 to 36 “
Water of crystallization 25 “
Potassium chlorid, potassium sulfate,
and insoluble 2 to 3 “
The content of potash, as is seen from the above formula, amounts to
from seventeen to eighteen per cent. The compound is completely dry,
is not hygroscopic, and is, therefore, always ready for distribution.
It is especially to be recommended for all those intensive cultures
where it is feared that chlorids and sulfates will prove injurious,
especially in the cultivation of tobacco.
=247. Potash in Factory Residues.=—The residues from the potash
factories in Stassfurt and vicinity contain considerable quantities
of potash and attempts have been made to recover this waste and put
it into form for fertilizing uses. The waste waters of the factories
are sometimes collected and evaporated, and the residue incinerated.
The content of potash in these residues is extremely variable, usually
quite low, and they, therefore, cannot be recommended for fertilizing
purposes, especially if they are to be transported to any distance.
=248. Quantity of Potash Salts Used.=—The total quantity of potash
delivered to consumers from the Stassfurt mines in 1891, the last
year for which complete statistics are at hand was 413,508 tons of
kainit and sylvinit, 39,444 tons of carnallit, 18,078 tons of sulfate,
and 12,453 tons of the potassium magnesium sulfate. Of the above
quantities, 115,245 tons of kainit were shipped to North America, and
of the high grade sulfate mentioned, 13,322 tons were sent to other
countries, and of the potassium magnesium sulfate, 11,081 tons were
exported.