l be about 60 or 65 per cent, of the weight tested, and
be colored with the iron always present in the adulterating substances,
and which is never found in pure guano. This test, to be accurate, must
be done with a nice pair of scales and a platinum cup, which may be
heated over a spirit lamp. Ten grains of the guano are placed in the
platinum cup, which is held by the tongs in the flame of the spirit lamp
for several minutes, until the greater part of the organic matter is
burnt away. It is allowed to cool for a short time, and a few drops of a
strong solution of nitrate of ammonia added, to assist in consuming the
carbon in the residue. The cup is again heated, (taking care to prevent
its boiling over, or losing any of the ash,) until the moisture is quite
evaporated. A full red heat must then be given it, when, if the guano be
pure, the ash will be pearly white, and will not exceed 3-1/2 grains in
weight. If adulterated with sand, marl, &c., the ash will always be
colored, and will weigh more than 3-1/2 grains. Even the simple burning
of a few grains of guano, on a red hot shovel, will often indicate by
the color whether a fraud has been committed; but we cannot particularly
recommend this method, as the iron of the shovel itself will sometimes
give a tinge to the ash. This might be obviated by burning the sample on
a common earthen plate.

If the adulteration of guano has been made by sand, it can be detected
by dissolving the ashes in muriatic acid. The sand will remain--if it is
more than one per cent., it has probably been added fraudulently. As
iron exists in loam, it will show in the color of the ash if that is the
substance used for adulteration. If lime has been added, it can be
detected by dissolving the ash in muriatic acid and separating the sand,
loam and iron, if present, by filtration, and then adding oxalate of
ammonia to the liquid. If it shows more than a mere trace of lime, it
has been falsified.

_Test by salt._--Saturate a quart of water and strain it; pour some in a
saucer and sprinkle guano upon the surface. Good guano sinks
immediately, leaving only a slight scum. If it has been adulterated by
any light or flocculent matters, they will be seen upon the surface of
the brine.

_Test by Acid._--Put a teaspoonful of guano in a wine glass and add a
little vinegar or dilute muriatic acid. If ground limestone or chalk
have been added, the effervessence will show it. A genuine article will
only show