Absorptive Properties of Soils. 
505 
by experiment it was necessary to determine tlie quantity of 
ammonia in the soils in three conditions : 
1st. In the natural state of the soil. 
2ntl. After being exposed to ammoniacal vapours. 
3rd. After h'Ang first digested Avith lime-water, and then 
exposed to ammoniacal vapours. 
To these three sets of examinations it seemed interesting to 
add a fourth, namely — 
4th. The quantity of ammonia left in the soil after liming, 
which process should have the effect of liberating it ; at all events 
in part. 
The operation of liming the soil has been already sufficiently 
described. In preparing the soils lime-water was digested with 
them in such relation that the lime should represent, as nearly as 
might be, 2 per cent, of the soil. 
After standing for 48 hours the clear liquid was drawn off, the 
soil was thrown on a filter, and repeatedly washed with distilled 
water to remove the excess of lime-water, the washing being con- 
tinued until the water coming away gave no trace of alkalinity. 
The soil was then dried and preserved for further experiment. 
The exposure to ammoniacal vapour was effected as follows : 
— Tlie soil was spread in a veiy thin layer on a sheet of paper 
at the bottom of a large cupboard ; in this cupboard a small open 
dish, containing water and lumps of carbonate of ammonia, was 
kept heated by means of a little gas flame. Sufficient air was 
admitted to cause a gentle circulation. The result of this arrange- 
ment was that the cupboard was filled with a moist atmosphere 
considerably charged with carbonate of ammonia. 
The soils were here exposed to the ammoniacal fumes for 
several hours in circumstances very favourable to its absorption. 
When the process was considered sufficiently complete the soils 
were removed, and exposed for 24 hours to the open air, to dis- 
sipate all ammoniacal vapour which might be mechanically 
retained amongst their particles. From smelling of ammonia 
pretty strongly when they were first removed, they came after- 
wards to show no signs of its presence iii a free or volatile state. 
To ascertain the quantity of ammonia present in the soil, both 
before and after these different operations, the soils were distilled 
in a chloride of calcium bath, with a mixture of caustic soda and 
powdered lime ; and the ammonia being received in a vessel con- 
taining hydrochloric acid, was afterwards converted into the well 
known platinum salt, and so determined. It is perhaps hardly 
necessary, in an agricultural periodical, to give the details of 
these experiments, but as they do not take up much space, and 
will remain unrecorded if not now published, it may be as well 
to give them. 
