23.66 47.52 51.93
Alkaline salts 10.70 3.73 3.43
Sand 3.80 11.65 8.20
------ ------ ------
100.00 100.00 100.00
Ammonia, 1.32 0.59 0.33

The deliberate adulteration of superphosphate, that is, the addition to
it of sand or similar worthless materials, I believe to be but little
practised. The most common fraud consists in selling as pure dissolved
bones, articles made in part, and sometimes almost entirely, from
coprolites. Occasionally refuse matters are used, but less with the
intention of actually diminishing the value of the manure as for the
purpose of acting as driers. It is said that sulphate of lime is
sometimes employed for this purpose, but this is rarely done, because
that substance is always a necessary constituent of superphosphate in
very large quantities; and as farmers look upon it with great suspicion,
all the efforts of the manufacturers are directed towards reducing its
quantity as much as possible. It is very commonly supposed by farmers
that the sulphate of lime found in so large quantity in all
superphosphates, and often amounting to as much as fifty per cent, has
been added to the materials in the process of manufacture, but this is a
mistake; it is a necessary and inevitable product of the chemical action
by which the phosphates are rendered soluble, although its quantity
depends on the materials from which the manure is made. When pure bones
are used its quantity is small, and it does not greatly exceed twice
that of the biphosphate of lime; but in a manure made from coprolites,
or other substances containing a large proportion of carbonate of lime,
which must in the process of manufacture be converted into sulphate, it
may be four or five times as much.

Although there is no manure which varies more in quality, or requires
greater vigilance on the part of the purchaser, in order to obtain a
good article, there is no doubt that superphosphates, owing to the
process of manufacture being better understood, and to increased
competition, have considerably improved in quality. Six or eight years
since a manure containing thirty per cent of phosphates, of which twelve
or fifteen had been converted into biphosphate