SOILS AND AGRICULTURE OF NORFOLK. 
363 
by the Kjeldahl method, where the soil is boiled up with 
strong sulphuric acid, which fixes the nitrogen as ammonium 
sulphate, the ammonia being afterwards distilled off and 
collected. Carbonates are estimated by measuring the 
amount of air displaced by the carbon dioxide liberated by 
acids when there is a considerable proportion of carbonates 
present in the soil, and by catching the carbon dioxide in 
soda (Amos’ modification of Reizet’s method), when the 
percentage of carbonates is under 1 or 2 per cent. 
For the other estimations, 20 grammes of finely-powdered 
soil are weighed out into a flask, 60 cc. of strong hydrochloric 
acid added, and the mixture heated for 48 hours at 100°C. 
The insoluble residue is filtered off, washed, and weighed, 
and the filtrate divided into two parts, one of which is 
evaporated to dryness, to drive off organic matter and acid, 
boiled for half an hour with water to extract potash, and 
again with acid for half an hour to extract phosphorus. 
The potash is weighed as potassium platini chloride, the 
phosphorus either titrated as ammonium phosphomolybdate, 
or weighed as phosphorus and molybdenum oxides. 
The other portion of the hydrochloric acid extract is made 
alkaline with ammonia filtered and washed, the precipitate 
being again dissolved, precipitated, and washed, and calcium 
and magnesium are weighed as calcium oxalate and 
magnesium phosphate. 
The mechanical separation of the various sized particles 
composing the soil is performed as follows : — The original 
sample of soil is dried, ground up with a wooden pestle in a 
large mortar, and the broken up soil passed through a sieve 
of 3 mm. mesh, all particles larger than that being reckoned 
as stones, and not counted in the analysis. 
Ten grammes of this soil are weighed into a beaker and 
allowed to stand for two hours with dilute hydrochloric acid 
to break up the aggregation of particles. The acid is then 
filtered off and the soil thoroughly washed and rubbed with 
