OXALIC ACID IN PERUVIAN GUANO. 
297 
to a certain point, after which the action slackens, and the 
decomposition is incomplete even after eight days. A little 
oxalic acid always remains in the liquid, easily recognisable 
by the fact that the precipitate which it gives with a salt of 
lime does not entirely disappear in acetic acid. The per¬ 
sistence of the oxalic acid is perhaps due to the fact that the 
phosphate of lime, not yet decomposed, is masked in a thick 
coating of oxalate of lime, which considerably retards the 
action of the oxalate of ammonia. 
' By acidulating with sulphuric acid the water serving to 
moisten the guano, so as to render the mixture freely acid, 
the decomposition becomes so much accelerated that it is 
finished in a few hours. No trace of oxalic acid is then 
found in the liquid, but in its stead an equivalent quantity of 
phosphoric acid. 
Acetic acid and water charged with carbonic acid act on 
guano in the same manner as sulphuric acid. 
M. Liebig has obtained the following results from a speci¬ 
men of guano remarkable for the small quantity of oxalic 
acid and the large quantity of uric acid (18 per cent.) it con¬ 
tained. Besides water, potash, soda, and ammonia, he found 
in the aqueous extract of 100 parts of guano— 
Phosphoric acid.2'857 
Oxalic acid ..4'202 
Sulphuric acid.3'371 
After having effected the transformation of the phosphate 
of lime by a little sulphuric acid, M. Liebig found that 4*2 
per cent, of oxalic acid contained in this guano had been re¬ 
placed by 3 per cent, of phosphoric acid ; that is to say, that 
by this method about half of the whole of the phosphoric 
acid of the guano had become soluble. 
In other Idnds of guano the same method has rendered 
soluble a weight of phosphoric acid corresponding to 10 or 
12 per cent, of the weight of the guano; in other words, the 
whole of the phosphoric acid contained in the guano. 
M. Liebig devotes the latter part of his memoir to exa¬ 
mining the practical conclusions to be drawn from these facts. 
When, he says, a field manured with guano receives too little 
rain to moisten the manure mixed with the arable land, all 
conditions are united to favour the solution of a certain 
quantity of the phosphoric acid, combined with the lime, 
and, consequently, to increase the fertilising action of the 
ammonia. The guano then acts in the same manner as acid 
phosphate of lime. 
Heavy and continuous rains, wLile washing the soil, disturb 
