20 R. H. Loughridge—Influence of Strength of Acid 
Art. IV.—On the Influence of Strength of Acid and Time of Dr- 
gestion in the Extraction of Soils; by R. H. LOUGHRIDGE, ol 
Oxford, Miss. 
THE following investigation was undertaken with a view of 
determining the extent to which the variations likely = occur 
in the extraction of soils by nydroshione acid, for the ose 
oe RST He, and with those made by similar eee 
and green 
n beginning the analyses of Mississippi soils in 1859, Dr. 
iieard adopted the following method, which has also been ad- 
hered to by his successors in this work, in over two hundred 
analyses made. 
The soil (ze, ‘fine earth”) is pulverized with a wooden Sectle 
and. thoroughly mixed. - e hygroscopic moisture is deter- 
mined, after exposing it in a space saturated with vapor, in a 
layer not exceeding 1™™ in a Ocoee, for twelve hours, by dry- 
ing at 200° C. ina paraffine bath. Of this dried substance from 
two to three grams are usually used in the general analysis, the 
methods employed being in general those adopted by Dr. Peter.* 
Tn another portion, after ignition, the phosphoric acid is deter- 
mined by Sgeaion for five days with nitric acid at 100° C., 
evaporation, precipitation by ammonium molybdate, hatiales 
at 100°, solution in ammonia and precipitation by magnesium 
sulphate. 
For general analysis the soil is digested in hydrochloric acid 
of strength 1-115 (as a rule) at 100°. It is then evaporated to 
complete dryness, this adding another day to the digestion. 
In the insoluble residue the soluble silica is determined by 
boiling with sodic carbonate. The alumina and ferric oxide 
are precipitated according to Rose’s method of boiling, for the 
oop separation of manganese, magnesium and calcium. 
The mixed precipitate is treated with potassic hydrate. 
fter precipitation of the lime by ammonic oxalate, the am- 
moniacal salts are destroyed by Lawrence Smith’s method, with 
aqua regia; and the residue converted into nitrates, from which 
sulphuric acid is recipitated by barium nitrate. The alkalies 
are then “es ted 
are separa 
* Ky. Report, vol. iii. . 
by treatment with oxalic acid, ignition and — 
washing. the sn te, barium, manganese a and magnesium 
