298 
. OXALIC ACID IN PERUVIAN GUANO. 
this decomposition; and it is to be desired, for the interest 
of science, that agriculturists would give some attention to 
the influence of guano, under these various circumstances, on 
the fertilisation of the soil. 
It is hardly necessary to remark that the action of guano 
can be made certain—at least, so far as it depends on the re¬ 
action of oxalic acid on phosphate of lime—by moistening 
the manure before using it with very diluted sulphuric acid, 
and then letting it stand for twenty-four hours. The 
moistened mass should have an acid reaction. 
The addition of water, to increase its weight, is the most 
common falsification of guano ; the greatest inconvenience 
arising from this fraud is, that it favours the decomposition 
above mentioned. The evaporation of ammonia proceeding 
from the phosphate of ammonia, formed under the influence 
of water, explains the loss of nitrogen observed in guano 
W’hich has been kept for any length of time. 
It is now evident that the agricultural value of guano has 
been but imperfectly appreciated, when the ammonia, phos¬ 
phoric acid, and phosphate of lime which it contains, have 
been estimated without taking account of the oxalic acid, to 
which, as M. Liebig has shown, its fertilising action is chiefly 
due. 
.This account would be incomplete without a description of 
the simple process by wLich M. Liebig estimates the oxalic 
acid in guano. The following is an extract from his letter 
on the subject:— 
To estimate the oxalic acid, I boil the guano with nitric 
acid; I then w'ash it; afterwards I add hydrochloric acid to 
the residue, wLich dissolves the remaining oxalate of lime 
and phosphate, leaving the uric acid. I neutralize the acid 
liquid w'ith ammonia, w hich precipitates the phosphate and 
oxalate ; I then add acetic acid, which dissolves the phosphate 
of lime, and throw the oxalate on a filter, wash it,^^ &c. 
Guanos can thus, in a very little time, be tested before 
being used .—Condensed from the Annalen der Chemie und Phar~ 
made, cxix, 11 .—Chemical News, May 17th, 1862. 
