Feb. 1, 1894.1 THE TROPICAL AGRICULTURIST. 
513 
per cent 
. 32-81 
. 71-62 
37-10 
. 80-99 
per cent. 
. 56-10 
. 87-83 
. 12-17 
Analyses of hifjhl y-conccat rated Superphosphates 
No. 1. 
Phosphoric acid soluLlc in water 
Equal to tiibasic phosphate of lime 
or 
Phosphoric acid soluble in citrate of 
aniuionia 
Equal to tri basic phosphate of lime ... 
No. 2. 
Biphosphate of lime 
Equal to soluble phosphates 
Insoluble phosphates 
If the price per unit of phosphoric aci<l in the 
above does not greatly exceed that in ordinary 
superphosphates, it is evident there would be a 
very material saving in freight, by the importation 
of such highly concentrated super])hosphates as 
compared with those of ordinary quality. 
Precipitated Phosphates. 
Another highly-concentrated form of phosphate 
of lime is sold as a manure under the name of 
precipitated phosphate. It is manufactured liy 
passing ammonia gas into superphosphate of lime, 
the result being a mixture chiefly of tribasic 
phosphate of lime and sulphate of ammonia. 
The sulphate of ammonia is removed by washing, 
and the dried residue contains from 70 to 80 
per cent, of tribasic phosphate of lime. 
Another method of manufacture is by the 
addition of lime to a solution of superphosphate, 
wliich throws down tribasic phosphate of lime 
along witli bi-phosphate. The tribasic phos- 
jjhate of lime obtained in this manner is much 
more soluble in ^\ ater (and therefore much more 
readily assimilated by plants) than is tribasic phos- 
pli.ate' of lime as it exists in mineral phosphates. 
This form of phosphate appears to be better 
suited for soils deficient in lime (like those of 
( 'eylon) than acid manures, and as a further recom- 
mendation it does not injure the bags in which it 
is packed like superphosphate. Its employment on 
Ceylon estates would altogether depend on its effec- 
tiveness and cost when compared with bone dust. 
Basic Slag. 
Another form of phosphate is deserving of 
notice which goes by the name of Thontas Basic 
Slag, the reputation of which has gone on steadily 
ri.sing. It is a slag ])rodnced in the manufacture 
of steel from pig iron by the Thomas and Gilchrist 
process. The slag consists chiefly of phosphate 
of lime, with excess of lime, the percentage of 
phosphate of lime varies from 30 to 42 per cent, 
but it can be purchased under the guarantee of 
containing phosphoric acid equal to 37 per cent, 
tribasic phosphate. It is sometimes sold in such 
a fine state of division, that 75 per cent of the 
powdered substance passes through a sieve of 168 
meshes* to the square inch, in this fine state 
Thomas phospliate of 40 per cent, tribasic phos- 
phate is said to 1)6 four times more soluble and 
effective than steamed bone meal (Grittiths). The 
unit of ])I\osphoric acid in this subst.ance is also, 
as yet, chciiier than iu nearly all other pliosphatic 
materials in England, but in Ceylon it could 
only compete with bone dust iu the event of its 
being found to l)e more efl'ective as tiie cost per 
unit of piiospliate of lime would be Kl-80 as 
against 110-70. It migiit be exi)ected to give 
especially good results on land deficient in lime 
aa it contains some free lime. The fact that it is 
compartively soluble and therefore reiidily assi- 
milated by plants is due to the phosphoric acid 
• It most effec'ive when ground much liner than 
this. It may with advantage be reduced to an impalp- 
able powder. 
existing not as tribasic phosphate, the most 
insoluble form whicl' phosphoric acid assumes, but 
combined with four molecules* of lime instead of 
three as in tribasic phosphate which renders it 
basic and more unstalile. It is worthy of remark 
that this manure contains oxide of manganese, 
which is not usually regarded as a necessary 
contituent of manures : but it is nevertheless 
a sul)stance which is always present in tea leaves, 
wliile it is not an abundant constituent of the 
soil. Dr. Grittiths in his work on manures, 
mentions that samples of good quality analysed 
by Dr. Voelcker and Mr. Bernard Dyer, show 
percentages of 19-12 and 19-94 respectively of 
]ihosphoiic acid, which are equivalent to 41-74 and 
43-33 per cent, tiibasic phospliate of lime. 
The following is a full analysis of basic slag of 
a more ordinary quality by Mr. Tatlock : — 
Analysis of Basic Slag. 
Lime 
Magnesia 
Oxiile of Iron 
Dxide of Manganese 
Alumina 
Silica 
* Phosphoric Acid 
Sulphuric Acid 
Sulphur as Sulphide 
Carbonaceous Matter 
per cent. 
. 47-65 
. 4-74 
. 12-56 
. 2-69 
. 4-58 
. 1202 
. 1509 
•27 
•15 
•25 
100-00 
32-94 
* Tribasic phosphate of lime 
POTASH MANURES. . 
The greater part of these manures, that are 
valued on the basis of their potash only, come 
from the German mines, prominent .imongst Avhicli 
are those of Stassfurth. The following analyses 
by F. Fursky (Bied. Centr. 1882> exhibit the 
composition of the Stassfurth manure salts. 
a> i 3 5 S . <o 
-5 a to ;3 =! !g 
5 2-S "-s^ 
■h CO 
IM 
Purified 
potas- 
sium 
sul- 
phate. 
0-1 00 0 10 
0 CO i-j 1 ^ 1 
Four 
times 
concen- 
Ijrated. 
.(i:i(,ciii I ! 
■10 0 lO I— 
. S-l 1 (M >« (N 
00 r^^ 
Thrice 
concen- 
trated 
potash 
niai;i- 
ures. . 
00 (M 0 00 0 
no 1 CO CO 
^ So ' 6i <h 
0 CM 
Concen- 
trated 
potash 
man- ! 
ures.'' 
111!! 
C5 m 0 >o 0 tc 
a: CO -H 05 CO 
ct (Tl Ol 
-HO) O-l W 
e9 
s a s 
,£5 
O 
e 
to 
eS 
* The name tetrocalcium phosphate has beeu given 
to thia combination to diatinguisb it froui orainary 
tricalcium phosphate. 
