‘ Sie OF ee ee 
- ~ pa 
350 HOW CROPS FEED. j 
posable silicates. A number of analyses which illustrate - 
these facts are subjoined: 
: 2. 3. 4. 5. 6. 
White | Bed | “tain | Pottery 
Sandy Loum. Clay. Clay. Clay. | Clay: 
HEIDEN. RAUTENBERG. Way. 
——— eee OO ee 
WV RiP Res we Rae wine ba eee 1.613 | 1.347 |. 6.15 6.39 | 10.36 6.18 
Oreanie matter... :....05. 2.3887 | 2.003 | none | none | none | none 
Sand and insoluble silicates.| 89.754 | 88.782 | 58.08 | 80.51 89.46 | 58.72 
(Clay, kaolinite)... 2. 0.052... (10.344) | (5.762) 
GUE ES ie eee SrIe Ff 2.630*| 4.199 | 18.73 6.80 0.04¢ | 18.41 
wf oxide Mf IPOH... s... ..-- 1.87 1.680 |} 2.11 0.90 0.14 5. 
Pil SANTINO LEG wale Spiele acc 1.152 | 1.288 | 12.15 4.35 F 13.90 ; 
el ree 0.161 122") Ore 0.38 0.12 0.61 
a ROMEME: 25 aes ,2)4 vs. 0.201 | 0.240} 0.29 0.17 0.08 0.43 
et POUAED «5 ok \aisisc veins aa ee 0.242 0.212 0.86 
J ete eee eae 0.034 | 0.141 | 1.41 
©, | Phosphoric acid........ 0.083 | 0.034 0.50: 1.37 
a | Sulphuric acid,......-.. 0.007 0.021 | none : : 
= Bebe acid, chlorine, 3 
and Mossi esse 2s tice ans 0.047 | 0.095 | none | 
100.000 |100.006 |100.00 |100.00 |100.20 1100.00 
* This soil yielded to solution of carbonate of soda before treatment with 
acid, 0.340 °|, silica. 
+ The silica in this case is the small portion held in the acid solution. 
The first three analyses especially, show that the soils 4 
to which they refer, contained a silicate or silicates in 
which iron, alumina, lime, magnesia and the alkalies ex- 
isted as bases. How much of such silicates may occur in 
any given soil is impossible to decide in the present state 
of our knowledge. In the soil, free silica, is usually, if not 
‘always present, as may be shown by treatment with solu- 
tion of carbonate of soda, but it appears difficult, if not 
impossible, to ascertain its quantity. Again, hydrated 
oxide of iron (according to A. Miiller and Knop) and hy- ~ 
drated alumina* (Knop) may also exist, as can be made 
evident by digesting the soil in solution of tartrate of 
soda and potash (Miller, Vs. Sé., ZV, p. 277), or in a mix- 
ture of tartrate and oxalate of ammonia (Knop, Vs. St. 
VITT, p. 41). Finally, organic acids occur to some ex- 
tent in insoluble combinations with iron, alumina, lime, 
® More probably, highly basic carbonates, or mixtures of hydrates and car 
bonates., 
