NEW “ TO IMPROVE THE SOIL AMD THE MIND.” SERIES 
"vol. II. ~~ ALBANY, AUGUST, 1845. No. 8. 
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MR. NORTON’S LETTERS—NO. XIV. 
Analysis of Slates—Importance of Chemical Investigation. 
Laboratory, of Ag. Chem. Association,) 
Edinburgh, May 30, 1845. j 
L. Tucker, Esq.—Among my other labors in the 
Laboratory, I have lately been engaged in an analysis of 
a series of slates, with a view to the agricultural capa¬ 
bilities of the soils formed by their decomposition. 
Such analyses are not ditfiult in performance, and are, as 
I hope to show, of great importance to the practical man. 
The seven slates of which I give the analyses, were 
from Wigtonsliire, in the south-west corner of Scotland, 
and were picked up at random by Prof. Johnston, during 
one of his journeys in that section. 
Without perplexing your readers by long descriptions 
of the process employed, I will only say that the pow¬ 
dered slate was first treated with muriatic acid, which 
dissolved the carbonates of lime and magnesia, and a large 
portion of iron and alumina. The remaining insoluble 
portion was then fused, and from it obtained the silica, 
the remainder of the iron and alumina, and the caustic 
lime and magnesia, all of these last having been in com¬ 
bination with the silica as silicates. 
The alkalies, that is the potash and soda, were deter¬ 
mined only by loss. The principal object sought was 
the lime, and this was determined with much care. The 
annexed tables will show, I think, that the investigation 
was not an unimportant one: 
No. 1. 
No. 2. 
No. 3. 
No. 4. No. 5. 
No. 6. 
No. 7. 
Silica,. 
Iron and Alumina 
60.13 
68.08 
57.53 
75.79 67.59 
j 
37. S2 
72.05 
sol. in Mur. acid. 
Do. obtained af¬ 
5.31 
5.51 
7.67 
6.43 4.82 
12.13 
7.09 
ter fusion,. 
13.93 
18.12 
22.29 
9.45 21.49 
39.41 
13.61 
Carb’te of Lime, 
12.77 
0.46 
3.54 
0.45 0.39 
0 34 
Barb. Magnesia, 
3.43 
0.39 
1.73 
2.15! 1.66 
0.35 
Caustic Lime,... 
0.24 
0.62 
0.30 
1.09i 0.43 
0.44 2.90 
6.50 
Caustic Magnesia 
1.25 
1.07 
1.89 
6.13 
2.79 
Alkalies and loss, 
2.94 
5-75 
5.05 
4.20 0-72 
4.01 
3.77 
100.00 
100.00j100.00 
100.00 J00.00 
100.00 
100.00 
The above figures represent the number of pounds in 
a hundred, the per centage. Thus, in No. 1 there are 
60 13.100 lbs. of silica, 12 77.100 lbs. carbonate of 
lime, &c. 
On one point I have not yet satisfied myself. I think 
that some of the lime dissolved by muriatic acid, was in 
the state of soluble silicate rather than carbonate, that is, 
in combination with silica in place of carbonic acid. 
This, if true, is important, and I am about to determine 
the fact, but shall not be able to give the result in this 
letter. 
It must be obvious, even to a person unacquainted 
with the nature of the substances above named, that soils 
formed by the decomposition of these slates must differ 
greatly in their composition; but to one who knows 
their properties it is no less evident lhat they must differ 
in their agricultural capabilities also. 
We will first notice the important ingredient of lime. 
All of that represented as carbonate, is in a state to be 
directly available for the food of plants. The caustic or 
quick lime, being in the insoluble part, would be more 
tardy in its operation. It is not to be despised however, 
for its action, though slow, is sure. We see as to the 
carbonate, that while No. 1 has 12.77 lbs. in a hundred, 
Nos. 2, 4, 5, and 7 have only from 3 to 4 tenths of a 
pound, and No. 6 has none, or merely a trace. 
The differences in the quantities of magnesia are also 
striking, and it is not unworthy of notice that there is 
generally more of it in the insoluble portion, represented 
as caustic magnesia, than in the state of carbonate in the 
acid solution. This being a necessary ingredient in a 
fertile soil; its presence is favorable, though in excess it 
is found injurious. In No. 6 there is perhaps too much of 
it, especially when we consider the small quantity of lime. 
The alkalies are also, as they should be, in considera¬ 
ble quantity, except in No. 5. The quantity of iron and 
alumina soluble in muriatic acid is as high as 12 per ct. in 
No. 6, and as a portion of the iron is in the state of pro¬ 
toxide, and soluble therefore in water, it might under 
certain circumstances accumulate in the subsoil to a 
hurtful extent. 
The proportion of these substances being so different, 
we see proved the importance of chemical investiga¬ 
tions. The above slates were taken from separate strata, 
all of which would probably be embraced within a cir¬ 
cle of 20 miles, and the soil produced by each would 
need a peculiar treatment. How absurd would be an 
attempt to cultivate all upon the same system, and yet 
such attempls are not unfrequent. It is in such districts 
as the one now under consideration, that we find contra¬ 
dictory accounts respecting the benefit resulting from the 
application of certain manures. For instance, a farmer 
upon the soil of No. 1 finds that the application of lime 
produces no good effect, while his immediate neighbor, 
upon another strata, such as No. 6, may say that lime is 
quite invaluable, that it doubles his crops. One there¬ 
fore, is an advocate for lime as an universal remedy; the 
other says that it is of no use whatever. Both are right 
as to their own cases, but are wrong in making a rule 
from one isolated instance, or even the experience of a 
limited district. 
Lime would no doubt be effective added to the soils 
of all the slates except Nos. 1 and 3, while sulphuric 
acid and bones would greatly benefit the whole of them, 
as supplying in addition to lime, sulphuric and phospho¬ 
ric acids, in both of which substances they are either de¬ 
ficient or contain them in very small quantities. My 
remarks might be extended to a very great length, and 
might embrace many points necessarily omitted, but ! 
will not trespass too much upon your columns. 
John P. Norton. 
