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Drying and Subsequently Washing with Water. If the guano, as is generally the case with those varieties that are brought from Peru and Chili, is a smooth and uniform powder, weigh out two ounces, spread it upon paper, and let it lie for two days in a moderately warm place, in summer a dry and airy situation, in winter in a warm room or chamber, in order that the air may dry it. What it may then have lost in weight must be esteemed mere surplus moisture. Many sorts of guano are so moist as to lose by this gentle drying from three to four drachms (20 to 24 per cent.) in their weight. Combustion. Pour half an ounce of the guano to be examined into at iron spoon, and place it upon red-hot coal until a white or grayish ash is left, which must be weighed after cooling. The lesp ash ]f behind, the better is the guano. Lime Test.Pour a teaspoonful of each guano to be examined into a wine glass, and upon this a teaspoonful of slacked lime ; then add a few teaspoonfuls of water and agitate the mixture briskly. Lime liberates the ammonia from the ammoniacal salts contained in the guano. The more excellent, therefore, a guano is, the stronger will be the pungent ammoniacal odor which escapes from this guano paste. Treatment with Hot Water.Half an ounce of the air-dried guano is placed in a filter made of blotting-paper, folded together in the shape of a cone, and this put into a funnel or wire filter, and scalding water poured over it until the water runs without color. If the paper with the moist guano is laid, when no more liquid drops from it, in a warm place, and the residue weighed when it has become completely diy, the deficiency from its original weight will show the weight of those elements which have been dissolved by the water. As a general rule it may be held, the larger the quantity of guano that is dissolved in water, the more ammoniacal salts does it contain, and the better it is. Hence that guano must be preferred, as in the test by combustion, which, upon being so treated with water, leaves behind the smallest residue. Vinegar Test.Pour strong vinegar over the guano to be examined, or, better still, some muriatic acid ; if a strong effervescence ensues, an intentional adulteration of the guano with lime may be inferred. This substance may also be recognized by the combustion test, since lime remains behind in combustion, and augments the quantity of ashes.
