On the Analysis of Guano. 
291 
proportionably less carbonate of ammonia in dislillation than the dung 
recently voided. Dr. Von Martius proceeds to compare the propor- 
tion of soluble salts in guano and pigeons' dung, and thinks that by that 
comparison alone he can establish the superiority of the former ; but he 
should have considered that the insoluble urate of ammonia, which is so 
powerful and copious a constituent of good guano, and is present in 
mucli smaller proportion in pigeons' dung, is sufficient of itself to turn 
the balance greatly in favour of the Peruvian manure. His general 
estimate however, that the manuring power of genuine guano is four 
times greater than that of pigeons' dung, is probably not wide of the 
truth. Besides the above-mentioned constituents, guano derives no 
small portion of its fertilizing virtue from the great store of phosphoric 
acid which it contains, in various states of saline combination, with lime, 
magnesia, and ammonia. Of all the principles furnished to plants by 
the soil, the pliosphates are, according to Liebig, the most important. 
They afford, so to speak, the bones and sinews of vegetable bodies, while 
ammonia supplies them with their indispensable element, azote. Their 
carbon, hydrogen, and oxygen are derived from the air and water. 
Those products of vegetation which are most nutritious to man and 
herbivorous animals, such as bread-corn, beans, peas, and lentils, con- 
tain the largest proportion of phosphates. The ashes of these vegetable 
substances afford no alkaline carbonates. A soil in which phosphates 
are not present, is totally incapable of jjroducing the above cereals. 
Agreeably to these views, Liebig believes that the importation of 1 cwt. 
of guano is equivalent to the importation of 8 cwt. of wheat ; so that 
1 cwt. of that manure assumes, with due culture, the form of 8 cwt. of 
substantial food for man. 
Since all these testimonies concur to place this remarkable excremen- 
titious product in such high estimation, it becomes a paramount duty of 
the chemist to investigate its composition, and to discover certain means 
of distinguishing what may be termed the sound or normal state of 
guano, from the decomposed, decayed, and effete condition. The 
analysis by Fourcroy and Vauquelin of a sample of guano presented to 
them by Baron Von Humboldt, gave the following composition in 100 
parts : — 
Urate of ammonia . . . , .9*0 
Oxalate of ammonia ..... 10*6 
Oxalate of lime . . . . . .7*0 
Phosphate of ammonia . . . . . 6*0 
Phosphate of ammonia and magnesia . . 2*6 
Sulphate of potash . . . . . 5'5 
Sulphate of soda . . . . . 3'3 
Sal ammoniac . . . . . .4*2 
Phosphate of lime . . . . . 14*3 
Clay and sand . . . . . .4*7 
Water and organic matters . . . . 32'3 
How different are the constituents from those assigned by Klaproth — 
a no less skilful analyst than the French chemists ! and how much this 
difference shows not c«ily the complexity of the substance, but its very 
variable nature ! 
The general results of an analysis by Professor Johnston, published in 
u 2 
