On the Analysis of Guano. 
297 
and fixed constituents of guano, is determined by igniting 100 grains of 
it in a poised platinum capsule. The loss of weight denotes the amount 
of combustible and volatile matter, including the moisture, which is 
known from a previous experiment. 
20. The insoluble matter is digested in hot water, thrown upon a 
filter, dried, and weighed. The loss of weight is due to the fi.xed alka- 
line salts, which after concentrating their solutions, are to be investigated 
by appropriate tests — 1. nitrate of barytes for the sulphates; 2. nitrate 
of silver for the chlorides and phosphates ; and 3. soda — chloride of 
platinum, for distinguishing the potash from the soda suits. 
21. The insoluble matter (of 20.) is digested with heat, in dilute 
nitric or hvdrochloric acid, and the whole thrown upon a filter. The 
silica which remains on the filter is washed, ignited, and weighed. The 
lime, magnesia, and phosphoric acid, which pass through in solution, 
may be determined as already pointed out. 
22. I have endeavoured to ascertain if muriate of ammonia be present 
in guano, by evaporating its watery solution to dryness, and subliming 
the residuum ; but I have never obtained a satisfactory portion of sal 
ammoniac ; and therefore I am inclined to think there is little of it. 
The quantity of chlorine to be obtained from guano is too inconsiderable 
to lead to a suspicion of its presence except in combination with sodium 
and potassium. Phosphate of soda is also a doubtful product — but if 
present, it may be obtained from the saline matter (of 20.) by acidulating 
it with nitric acid ; precipitating first with nitrate of barytes, next with 
nitrate of silver, taking care to use no excess of these two re-agents, then 
supersaturating the residuum with ammonia, and adding acetate of mag- 
nesia, when the characteristic double phosphate of this earth should fall, 
in case phosphate of soda be present. 
By the preceding train of researches, all the constituents of this com- 
plex product may be exactly disentangled and estimated ; but they mani- 
festly require much care, patience, time, and dexterity, as also a delicate 
balance, particularly in using the appropriate apparatus for generating 
the potential ammonia, and for measuring the whole of this volatile sub- 
stance, separated in the several steps of the process. It may be easily 
imagined how little confidence can be reposed in many of the analvses 
of guano, framed, I fear, too often with the view of promoting the sale 
of an indifferent or even a spurious article of commerce. 
A. — I shall now give in detail my analytical results upon three dif- 
ferent samples of good South American guano ; and next the general 
results upon three samples of African and Chilian guanos : — 
1. Guano from Bolivia, imported by the Mart/ and Anne. This 
sample was taken by myself, as an average of several bags in the lighter, 
before the cargo was landed. Pale yellow colour, dry, partly pulveru- 
lent, partly concreted in small lumps, with a few small fragments of 
granite, which being obvious, were separated prior to the analysis. Spe- 
cific gravity of the pulverulent portion, witliout granite, 1"60; of the 
concretions, 1 "66 ; mean, 1 '63. Water digested on the former portion 
is neutral to litmus-pa])er ; on the latter, it is faintly acid. 
2. 100 parts lose 6 5 by the heat of boiling water, and exhale no am- 
monia. When digested and triturated with cold water 30-5 parts dis- 
solve and 69 '5 are obtained after drying at 212°. Of those 30*5 parts. 
