are apt to contain caustic alkali, which would tend to
drive off the ammonia in a volatile state.

It has been recommended, in order to save trouble and effect equal
distribution, that the manure to be applied should always be made up to
the same amount, so that the farmer by experience may ascertain the rate
at which to apply it. And here it may be well to say a word or two on
the subject of mixing manures--a subject with which the farmer is not
always so conversant as it is desirable in the interests of his own
pocket he should be.

_Mixing Manures._

It is to be feared that not unfrequently indiscriminate mixing may cause
very serious loss in the most valuable constituent of a manure. It may
be well, therefore, to point out one or two of the causes of the loss
that is apt to ensue on the mixing of different kinds of manures
together.

As the subject depends for its clear comprehension on certain chemical
elementary principles, it may be well for the benefit of non-chemical
readers to state these pretty fully.

_Risks of Loss in Mixtures._

The risks of loss which may occur from the mixing of artificial manures
together may be of different kinds. One is the risk of actual loss of a
valuable ingredient through volatilisation; another is the risk of the
deterioration of the value of a mixture through change of the chemical
state of a valuable ingredient. Undoubtedly the most common and most
serious source of loss is the former. Of the three valuable manurial
ingredients--nitrogen, phosphoric acid, and potash--only the first is
liable to loss by volatilisation, and this generally only when the
nitrogen is either in the form of ammonia or nitric acid.

_Loss of Ammonia._

Ammonia, when uncombined, is a very volatile gas with a pungent smell, a
property which enables its escape from a manure mixture to be very
easily detected. It belongs to a class of substances which are known
chemically as bases, and which have the power of combining with acids
and forming salts. Sulphate of ammonia is a salt formed--as its name
indicates--by the union of the base, ammonia, with the acid, sulphuric
acid. Now when ammonia unites with sulphuric acid and forms sulphate of
ammonia, it is no longer volatile and liable to escape as a gas, but
becomes "fixed," as it is called.

Although most salts are more or less stable bodies--not liable to
change--if left alone, and not submitted to a high temperature or
chemical action, th