July 1, 1903.] THE TEOPICAL AGRICULTURIST. 
5 
an acidity absolutely below that of the sap of any 
of the 103 plants examined by Dr. Dyer in the 
paper referred to> and it also more closely approxi- 
mates to the natural acidity of ordinary soils than 
either of the standard solutions previously employed. 
It is therefore contended that any phosphoric acid, 
lime or potash, dissolved out by this standard 
solution, may fairly be regarded as existing in a 
form available aa plant food, whether in a soil or in a 
manure. In the following Table, the relative solubi- 
lity in this standard solution of five different kinds 
of finely ground ro^w posphate, is compared with 
that of a good specimen of basic slag. In each 
case, one gramme of the ground phosphate waa 
exhausted with 1,000 grammes of cold distilled water, 
in which one gramme of crystallised citric acid had 
Ijeen dissolved. After stsnding 24 hours with occa- 
sional stirring, the insoluble portion was filtered off, 
ignited and weighed, while the proportions of lime 
and phosphoric acid were detei mined in the clear 
solution. 
MiNEEAL Phosphates. 
Solubility in cold vtoh solvji.on of Citric Acid (1 in 
1,0.0) after 24 hours. 
J3 
o 
a 
<o 
n 
ca 
fa 
<D 
'S 
lori 
a 
<i 
Total phosphate ) ^o gg 55.99 73.26 79 57 61-23 38 97 
of lime present j oa m 
Fine powder-i 
passed through \ 76 21 67-69 72 37 91-63 93-61 83- 80 
100 hole sieve... J 
Portion soluble 
in citric aci 
solution. 
le-j 
id V 30- 
GO 30 00 22-60 22 80 31-40 S8 80 
Containing— 
Solnble lime.... 15 34 13 66 H.87 11-64 15 23 22 17 
^thorlc 2-85 6 35 62 5 8-40 9 90 8 70 
""Ihate of Ce } - l^-Ol 18 34 21 61 18 99 
The above res'jlts show the percentage of phos- 
phate of lime preseut in the respective sf.mples, also 
the fineness of the grinding, the extent to which 
the respective specimens were dissolved by the 
col"', weak citric acid solution, and finally, the pro- 
portionf- of lime and phosphoric acid in i!s equi- 
valent of phosphate of lime existing in the cold 
citric solution. 
It will be seen that ground phosphates are only 
soluble, and therefore available as plant food to the 
txtent of 22-60 to 31-40 per cent., and that the 
basic slag is only dissolved to the extent of 38-80 
per cent., in fact only little more than one-tLird 
of its weight, though 11 waa of good quality, B8-S7 
phosphate of lime and 83-80 fineness. Aa reparda 
the actual amount of phosphatee if lime dissolved 
out of the five specimens, the Petce River, with a 
fineUfeSB of 93-61,' gave the highest fi- ues for solu- 
bility, there being 21-61 phosphate oi I me dissolved 
ont of a total of 61-23. lu the case of basic slag, 
the figures, though relatively higher, are actually 
less, namely, 18-99 phosphate of lime dissolved out 
of a total of 38-97. These results explain why Pro- 
fessor Jamieton, with the black vegetable mould to 
pxperiment upon, obtained an appreciable increase 
in the jieldof turnips from the application of finely 
ground raw phosphates, though if we take the most 
favourable example, namely, Peace River, only about 
one-third of the total phosphates would have been 
utilised as available plant food f.nd the remaining 
two-thirds was of no use to the crop. The defect 
in the economical srplication of finely-K'ound phos- 
phates if" their insufficent solubility, and it is this 
want of solubility that is the defect alfo of basic 
slag whe-a applied to many soils. Before leaving 
these fifurts it is interesting to note that it ia 
only iu the proportion of soluble lime that basic 
slsg shows a superiority over that cf Peace River 
phosphate, there being- 22-17 per cent, dissolved out 
as against 15-23. Indeed, the fertilising value of 
ordinary basic slag must be ascribed as very largely 
due to the ready supply of lime when the slag is 
brought in contact with aonr soil, if accompanied 
by plenty of water either iu the soil or frcm the 
rainfrtll. It is well kuo-wn that slag fnils to produce 
any practical results on certain soils, and this failure 
is probahly due partly to a deficient supply of 
water and partly to the absence of tbat excess 
of vege^uble matter which is necessary to produce 
an acid solvent. 
The New Manuee Basic Supeephos-phate. 
It occurred, theiefore. to the authoi , af er careful 
consideriiticu in the autumn of lyOO, that a new 
and useful manure could be produced by the careful 
admixture in suitable proportiors of orflinar; acid 
superphosphate with finely ground or slacked lime. 
After making numerous trial mixtures the most 
suitable proportion were decided upon, and a nsanura 
was produced which possessed a distinctly alkaline 
or basic character, and at the same time supplied 
from 25 to 27 per cent- of phosphate of lime in a 
form readily soluble in the standard solution (1 in 
1,000) of citric acid. The manure so produced was 
appropriately called basic superphosphate bees use 
it combined the alkaline nature of slag with the 
wellknown aolubility of superphosphate. The me- 
chanical condition is superior both to that of baeic 
slag and superphosphate. Compared with the former 
it is much more bulky and lighter in weight, 
so that if equal weights be placed in two glasi 
tubes about i foot long basic superphosphate will 
be found to occupy a spnce of 11 inches as compared 
with only 4i inches occupied by basic slag, the 
relation in round numbers being aa 100 to 40. 
Compared with superphosphate the new material is 
very much drier, containing only 4 to 5 per cent, 
of moisture instead of the 14 to 18 per cent, unusually 
found in commercial superphosphate. Being in a 
finely ground dry powder of light weight and bulky 
nature, greater uniformity and more perfect distri- 
bution can be obtained than is possible with basic 
slag, which when sown by hand ia apt to drop between 
the fingers before complete delivery can be effected. 
Farmers will appreciate these advantages, and will 
be glad to be assured that there will bo no danger 
of any clogging of the drill from damp condition, 
which in the case of badly made superphosphate 
is a very serious defect, and renders the uniform 
distribution of the manure quite impossible. The 
general composition of basic superphosphate may be 
gathered from the following analysis :— 
COMPOSITIOK CF Basic PuPEIiPHOSPHATE. 
MMstnre (lost at 212° F.) 4-15 
Combined water and loss on igni- 
tion 12-86 
♦Phosphoric acid (total) .. .. 13 60 
Lime .. .. ... ... .. 35-15 
Sulphuric acid 28£0 
Oxides of iron, alumina, magnesia, 
&c 2-34 
Insoluble siliceona matters ... 3-40 
100-00 
*Eciual to phosphate of lime „. 29-68 
The manure usually contiina from 33 to 35' per 
cent of total lime, so tbat in this respect ha&ie 
