ALKALIES. 
most conspicuous figure in agricultural chemis- 
try, are ammonia, potash, and soda. Ammonia 
is popularly called the animal alkalz, because con- 
tained in animal substances; potash, the land 
vegetable alkali, because contained in land vege- 
tables; and soda, the sea vegetable alkali, because 
contained in sea vegetables ;—ammonia, the vola- 
tile alkalt, because it naturally flies off in vapour ; 
and potash and soda, the jized alkalies, because, 
in all ordinary conditions, they resist evaporiza- 
tion. But these three principal alkalies require 
a little additional definition ; and a large number 
of other alkaline substances require to be brought 
into view. Ammonia consists of hydrogen and 
nitrogen, is obtainable in a separate form only by 
chemical operation, exists naturally in the exu- 
dations, the urine, and the excrements of animals, 
evaporates into the atmosphere so as to mix gase- 
ously with the air and in rain, and, even when 
artificially obtained, is usually met with only in 
such combinations as constitute liquids or salts. 
Potash and soda, though long supposed to be 
simple substances, and regarded as unique in 
both character and action, are now known to be 
metallic oxides; potash consisting of oxygen and 
a metallic substance called potassium, and soda 
consisting of oxygen and a metallic substance 
called sodium. Various other alkaline bodies are 
constituted in a manner precisely similar to pot- 
ash and soda, and are designated alkaline oxides 
or alkaline earths. Lime, one of the most impor- 
tant examples of these, consists of oxygen and a 
metallic substance called calcium ; and magnesia, 
| another important example, consists of oxygen 
and a metallic substance called magnesium. Yet 
lime and magnesia, in this primary and proper 
sense of alkaline earths, must not be confounded 
with the lime and the magnesia of popular phra- 
seology; for these are carbonates of lime and 
magnesia, and hold the alkaline matter of the 
earths in a state of dilution and alteration by 
chemical union with carbonic acid. Even the 
alkalinity of the true alkaline earths is far less 
active or powerful than that of potash and soda. 
Yet, with the exception of magnesia, all the 
alkaline earths, as well as potash, soda, and am- 
monia, are acrid to the taste, and have a caustic 
action on the skin. Another important class of 
alkaline substances exist as characteristic con- 
stituents of certain plants, are produced in these 
plants during the progress of vegetation, and 
bear the general designation of alkaloids, or 
vegeto-alkalies. They consist of various, yet in 
each instance, definite proportions of oxygen, car- 
bon, hydrogen, and nitrogen; and yet though so 
very differently constituted from ammonia, they 
possess a considerable resemblance to that power- 
| ful and unique alkali in their alkaline properties 
and modes of chemical action. See ALKALINE 
Bases. Ammonia evaporates at a very low tem- 
perature, and is decomposed at a high tempera- 
ture ; potash, soda, and the other alkaline oxides 
resist the evaporating power of comparatively | 
high temperatures, and, though they may imbibe 
oxygen, are not decomposed by the action of heat 
in the open air; and all the alkaline bases or 
alkaloids are decomposed at high temperatures, 
and yield up their constituent elements to the 
formation of new compounds. All the alkalies 
readily combine with acids to lose their own 
alkalinity of action, to destroy the acidity of the 
acids, and to form new substances called alkaline 
salts; and ammonia and many of the alkaline 
oxides combine with metallic oxides—as am- 
monia with the oxides of cobalt, copper, and 
nickel, and potash and soda with silica, alumina, 
and the oxides of lead and zinc—to form another 
class of latently alkaline substances. The alka- 
line salts perform a part in the laboratory of the 
soil and in the chemistry of vegetation, second in 
importance only to the alkaline oxides them- 
selves,—being readily decomposed by chemical 
forces which there attack them, and freely giving 
out their elements to act chemically upon the soil 
and alimentarily upon plants. 
Argillaceous or clayey earth—such mineral 
matter as contains a proportion of alumina or the 
concentrated principle of clay—forms a compo- 
nent part of by far the greater portion of fertile | 
soils ; and in any rare instance in which it is ab- 
sent from land capable of cultivation, some 
source, either natural or artificial, exists for the | 
supply of its characteristic elements. Now the 
whole fertilizing power of this earth consists in 
its invariably containing alkalies and alkaline 
oxides, with sulphates and phosphates. Alumina 
exercises an influence on vegetation, not by 
chemical action upon accompanying earths, nor 
by mechanical control over the roots, nor by en- 
tering the organism of the plant, nor by forming 
an element in its substance, but by attracting 
and retaining water and ammonia, and by yield- 
ing up its potash or soda to exert their directly 
alkaline influence upon surrounding silicious 
matters in the soil, and upon the juices, secre- 
tions, and general vegetation of the plant. 
Liebig, “it must be remembered that felspar con- 
tains 172 per cent. of potash, albite 11°43 per 
cent. of soda, and mica from 3 to’5 per cent., and 
that zeolite contains from 13 to 16 per cent. of 
alkalies. The late analyses of Ch. Gmelin, Lowe, 
Fricke,. Meyer, and Redtenbacher, have also 
shown, that basalt and clinkstone contain from 
2 to 3 per cent. of potash, and loam from 14 to 4 | 
per cent. of potash. If now we calculate from 
these data, and from the specific weights of the 
different substances, how much potash must be 
contained in a layer of soil, formed by the disin- 
tegration of 26,910 square feet of one of these 
rocks to the depth of 20 inches, we find that a 
soil of felspar contains 1,152,000 lbs., of clinkstone 
from 200,000 to 400,000 lbs., of basalt from 47,500 
to 75,000 lbs., of clay slate from 100,000 to 200,000 
Ibs., and of loam from 87,000 to 300,000 lbs.” 
66 In | 
order to form a distinct conception of the quan- | 
tities of alkalies in aluminous minerals,” says Dr. | 
