550 
Oil the Food of riants. 
matter, water is then poured upon the mass, and the whole placed upon 
a filter ; the solution is next to be neutralised with nitric acid and acetate 
of lead poured in, which throws down sulj)hate and phosphate of lead. 
The mixed precipitate is collected on a little filter, washed, suspended in 
water, and decomposed by a stream of sulphuretted hydrogen gas. 
After warming and filtration the solution is neutralised by ammonia and 
tested for phosphate by nitrate of silver, and sulphate of magnesia with 
excess of ammonia. 
The latter test is an exceedingly valuable one, as it often happens that 
the quantity of phosphate is very small, and the chloride has not been 
wholly got rid of by the above process ; in such a case nitrate of silver 
will act equivocally. By adding to the suspected solution, however, in 
succession, a drop of solution of sulphate of magnesia, a little sal- 
ammoniac, and then an excess of ammonia, a precipitate of the triple 
phosphate will make its appearance if })hosphoric acid be present at all. 
All the soils which I have examined, treated in this way, yielded 
phosphoric acid : from garden-mould the quantity was really very 
considerable. 
Jt is almost unnecessary to add that if gravel or large vegetable fibres, 
and such accidental substances, exist in the soil exammed, they must be 
separated by a sieve and an account kept of them. 
The following will serve as examples of the application of the 
process : — 
No. 1. — Old grass-land from Hanbury, Worcestershire: — 
500 grains by drying at 300" Fahr. lost . . 12 '4 grains. 
By elutriation, &c. it gave — 
Siliceous sand contaming much oxide of iron 2.'i6"0 „ 
Finely divided matter .... 229 ' 6 
Soluble substances — 
Organic . . . O'l grains. 
Inorganic . . . 0'5 „ 
Water 12-4 ', 
499-2 
Finel} -divided matter analysed by the method described : — ■ 
25 crrains gave — 
III 100 parts. 
Silica 
. 17'1 
. 68-4 
Alumina 
2-55 
. 10-2 
0.x idc of iron 
2-95 
11 -s 
Carbonate of lime . 
0-2 
0-8 
Carbonate of magnesia . 
0-1 
0-4 
Organic matter, " humus " 
0-9 
3-6 
Potash, by lime process . 
r02 
4-08 
Loss .... 
0-18 
0-72 
25-0 
. 100-0 
D'fctinct evidence both of phosphoric acid and of ammoniacal salt. 
