308 



On Guano. 



water as in four days to be 5 per cent, heavier than it had been 

 before it was exposed to heat.* 



This evolution of its volatile constituents by exposure to the air 

 is well known on the coast of Peru. From the guano island near 

 Arica such a stench proceeds that vessels are prevented by it 

 from anchoring near the town (Feuille and Humboldt) ; while 

 the white guano at the present day sells in the port of MoUendo at 

 a price more than one half higher than that which is given for the 

 dark-grey and the red ( Winterfeldt). 



I do not know in what way the guano is shipped for transport 

 to this country ; but it is certain that^ were it rammed hard into 

 casks as soon as it is taken from the mine, and so kept in this 

 country till it was about to be applied to the land, it would neither 

 be so far deteriorated by the loss of its volatile constituents, nor 

 increased in weight by the absorption of water. 



5. The absolute quantity of ammonia contained in the guano of 

 Klaproth and Vauquelin is not stated. In the analysis published 

 by Mr. Macdonald as above given, it is said to amount to 15 per 

 cenl.f This greatly exceeds the quantity contained in the specimen 

 examined by myself, which gave me only. 7 per cent, of pure 

 ammonia. The same is true of the uric acid, which in my spe- 

 cimen did not amount to 1 per cent.J In these results a certain 

 latitude must be allowed for necessary differences, since the older the 

 deposit, the less rich must the guano be in uric acid and ammonia. 



6. An important ingredient in the guano is the phosphate of 

 lime, and as this substance is neither volatile, so as to rise into the 

 air, nor soluble, so as to be washed out by the rains, it is obvious 

 that the older the deposit and the less volatile matter it contains, 

 the richer it is likely to be in this earthy phosphate. Supposing 

 each specimen free from sand, &c., the analysis of Klaproth 

 gives 14"7 per cent, and that of Vauquelin 15 per cent., while 

 the bone-earth in the third analysis is stated at 30J per cent. 



In two portions which I examined, the phosphate of lime 

 amounted in the one to 29, and in the other to nearly 43 per cent, 

 of the guano supposed to be free from sand. In regard to this 



* If a little guano powder be mixed in a wine-glass with a little newly- 

 slaked lime, ammonia is immediately evolved, and becomes distinctly sensible 

 to the smell. 



f Fifteen per cent, of pure ammonia are equal to 60 of bicarbonate of 

 ammonia, 45 of sal ammoniac, or 40 of oxalate of ammonia. As much of 

 the ammonia in guano exists in the state of bicarbonate, I doubt if any of 

 the specimens which come to this country can ever contain so much as 15 

 per cent, of pure ammonia. 



% One hundred grains of guano distilled with dilute caustic potash, and 

 the ammonia received into dilute muriatic acid, yielded, on evaporation at 

 212°, 2r5 grs. of sal ammoniac, equal to about 7 grs. of ammonia. The uric 

 acid was separated by boiling in dilute caustic potash, and precipitating 

 by dilute sulphuric acid. 



