Aug. 1, 1901.] THE TKOPICAL AGEICULTUEIST. 
75 
of manufacture, for lime is only added in sufficient 
quantity to remove the phosphorus and silica 
existing in the original iron ore. 
Probably 2 or 3 per cent, of caustic lime is the 
utmost present, for moat of the lime not combined 
with phosphoric acid exists as silicate of lime in a 
form readily soluble in weak solutions of vegetable 
acids, but not soluble in ordinary water, as may 
be easily demonstrated by actual trial. 
The Preparation of Basic Superphosphate. — Bearing 
all the before-mentioned points in mind it occurred 
to the author that a manure, superior to ordinary 
basic slag in regard to its solubility, and at the 
same time combining its alkaline character, could 
be prepared by the addition of lime, preferably 
slaked lime, to ordinary superphosphate in sufiBcient 
quantity to convert such acid superphosphate into 
alkaline or basic superphosphate. 
Experiments were accordingly made, and, it being 
found that the addition of lime in proper proportions 
did not render the soluble phosphates insoluble in 
very weak cold solutions of citric acid ( 1 in 1,000>, 
such as might be expected to exist in certain soils, 
t, provisional specification was at once filed and 
eventually a patent as granted. 
!!2,The preparation in theory is very simple, but 
in practice there are certain mechanical difficulties 
to be overcome in order to effect a uniform and 
complete admixture of the acid superphosphate 
with the caustic lime. 
The quantity of slaked lime required to be added 
depends upon its quality and the care with which 
it has been burned in the kiln. No particular 
degree of purity is necessary, but by preference 
the best commercially available is to be employed. 
The orginal specimen of basic super was prepared 
from a super having the following composition; — 
, Per Cent. 
So'able phosphate 27-72 
Insoluble phosphate 4 82 
This would be regarded as a somewhat wastefully 
made quality, having nearly .5 per cent, of undissolved 
phoaphate ; but it was found that a considerable 
portion of such phosphate, though insoluble- in 
ordinary water, was readily soluble in weak solution 
of citric acid (1 in 1,000). 
About 85 parts of the super were thoroughly 
mixed with 15 parts of good slaked lime and allowed 
to remain in a heap for fully 21 hours. Next day 
1 grm. of the manure, with 1 litre of standard 
solution containing 1 grm. of citric acid, was 
placed in a large beaker, and, with occasional 
stirring, wa» allowed to stand for 24 hours, no 
artificial heat whatever being applied. On the 
following day the solution was filtered, the portion 
left insoluble was burned and weighed, and the 
filtrate carefully analysed for lime and phosphoric 
acid, with the following results: — 
* Portion soluble in citric acid solution 94 70 
t Portion insoluble (after burning) in citric 
solution .. .. 5'30 
•Containing soluble lime ... 34-66 
do phosphoric acid ... 12'0i 
Equal to phosphate of lime 26-19 
t Containing insoluble lime ... 2*40 
do phosphoric acid ... 0-65 
Eqnal to phosphate of lime 1-41 
According to calculation the sample so prepared 
should have contained — 
Ordinary soluble phosphate ... 23-56 
Ordinary insoluble phosphate ... 4-09 
But the actual results obtained by treatment 
with the standard citric acid solution were — 
Soluble phosphate ... 26-19 
Insoluble phosphate ... 1-41 
Consequently 2'68 per cent, of the phosphate 
originally insoluble in warm water was found to be 
readily soluble in the cold weak citric acid 
solutiou employed. 
Table II. 
llorls Samples of Basic Superphosphate as actually 
prepared in Eiujland, Ireland, and Scotland. 
12 3 4 
' Portion soluble in Treek 
cit;ric acid solution. 94-60 94-20 93-00 92-60 
Portion insoluble in same 
(after burnins). 5-40 5-=0 7-00 7-iO 
* ContiinlDs— 
Soluble lime 33-93 36-73 3-2-53 29-56 
Soluble phosphoric 
acid 13-60 13-35 12-00 12-45 
Equal to phosphate 
of lime 29-68 29-14 26-19 ;7-18 
Manufacturers hitherto have never been paid any- 
thing on account of the so-called insoluble phosphate 
in superphosphate. 
When made from materials like Tennessee rock 
phosphate, containing 4 to 4i- per cent, of oxide 
of iron and alumina, there must always be a 
considerable proportion of phosphoric acid retained 
in a form insoluble in water, but readily soluble in 
weak vegetable acids, and therefore probably 
available as plant food. 
It is intended that the quality sent out shall 
average 25 to 27 per cent- of such so-called soluble 
phosphate, and that the manure shall always have 
a distinctly alkaline reaction. 
Basic super is much more soluble in ordinary 
water than basic slag, as may be easily ascertained 
by treating 1 grm. of each with a litre of cold 
distilled water, allowing the same to remain in 
contact for 48 hours, with occasional stirring, and 
subsequently filtering off the insoluble portions and 
analysing the filtrate as follows : — 
Table III. 
Relative Solubility in Cold Water after 48 hours, 
Basic Super Basic Sla? 
* Portion sol ubl* 66-80 6-60 
Portion insoluble (after burning) 33-20 93-40 
* Containinj— 
Soluble lime 22 28 4.7t 
No pho.sphate soluble in Wiiter. 
These results demonstrate the superior solubility 
of basic super and also may explain why basic slig 
fails on soils which do not contain an excessive pro- 
portion of accumulated vegtable matter. 
It is not ordinary water, but water largely im- 
pregnated with vegetable acids, that is capable 
of dissolving a hard fusbd mass like slag. Ordinary 
water has but a slight action on slag, however finely 
ground it may be. 
In this case the slag was very well greund, having 
a fineness of 83-88 and containing .?8-97 per cent, 
of phosphate of lime. 
Table IV. 
Comparative Soltibility in Ammoniacal Citrate 
of Ammonia 
Taking 1 grm. of phosphate, 2^ grms. citrate of 
ammoni*, and 10* c.c. water, gradually raised to 
boiling point and filtered, and the insolube portion 
burned and weighed. 
Ba»ie Super Basic Slag 
* Portion soluble 86 70 28-9* 
Portion in.soluble (aft«r burning) 13-30 71-10 
* Coufcaining— 
Soluble lime 32-0! 14-71 
Soluble phospliosphoric acid... 10 20 ;<-35 
Equal to phosphate of lime 22 27 /-SI 
The above results show that basic super is very 
readily dissolved by citrate of ammonia solution 
(slightly ammoniacal), while basic slag is only very 
slightly dissolved, though containing originally » 
higher percentage of phosphate of lime. 
Mechanical Condition, — As may be expected, the 
condition of basic supper is excellent, being a dry 
powder easily distributed either by hand or machine; 
and the farmer need not fear that clogging in the 
drill, resulting from damp condition, which is such 
a dilBcult matter to overcome. 
The light bulky character of the material as com- 
pared with the heavy nature of slag may be coH' 
