206 
Peruvian Guano. 
Before treatment this guano contained 28 38 per cent, of phos- 
phates, and in this quantity only 5*05 per cent, in a soluble state, 
and 23*33 per cent, as insoluble phosphates. These figures 
show the great utility of mixing guano with a little oil of vitriol. 
The acid not only fixes any free carbonate of ammonia (which 
in damaged or in wet guano may amount to more than If- per 
cent.), but it has also the more important effect of rendering 
soluble a large proportion of the insoluble phosphates. 
2. When guano is exhausted merely with water, the portion 
insoluble in water is found on analysis to contain very little 
oxalate of lime ; in that case nearly the whole of the oxalic acid 
in guano remains in the watery solution. But when guano is dried 
with only 5 per cent, of sulphuric acid, nearly the whole of the 
oxalic acid is left behind as oxalate of lime in the portion insoluble 
in water, and an equivalent proportion of phosphoric acid is 
liberated from the insoluble phosphates and passes into solution 
in combination with ammonia and potash. 
3. It will be noticed that, of the total amount of nitrogen in 
this sample of sulphated guano, three-fourths is present in a state 
soluble in water, and only one-fourth is insoluble. There can, 
however, be no doubt that these insoluble nitrogenous com- 
pounds become readily transformed into soluble combinations, 
which are easily assimilated by plants. 
Composition of Peruvian Guano dried on a Waterbath with 10 per ccr.t. 
of Oil of Vitriol (S0 3 , H 0). 
Water given off on long drying at 212° Fahv 4'58 
Bi-phosphate of lime 1*51 
Equal to bone-earth rendered soluble (2'37) 
Sulphate of lime 2-09 
Alkaline salts 10-96. 
Containing phosphoric acid (7 - 09) 
Equal to tribasic phosphate of lime (15 - 36) 
*Soluble organic matter and salts of ammonia .. .. 4G-45 , 
■flnsoluble organic matter 7'28 "j &ej c 
Insoluble phosphates 12 - 24 [ n p -g 3 
Oxalate of lime 13-33 [ 1 1 ? jg 
Insoluble siliceous matter 1*56 J £ -~ 
-2 si 
2 o 
to - 
« o 
100-00 
♦Containing nitrogen 12-00 
Equal to ammonia 14'57 
■""Containing nitrogen 3 - 43 
Equal to ammonia ..' 4-1C 
As might have been expected, the guano by the addition of 
10 per cent, of acid is rendered slightly more soluble than by 
5 per cent. 
The effect produced by the larger amount of acid, however, is 
scarcely commensurate to the increase of acid ; for, with 10 per 
