o4 MONTHLY. 
xxr. 
COLOMBO, AUGUST 1st, 1901. 
No. 2. 
BASIC SUPERPHOSPHATE: ITS PRE- 
PARATION AND USE AS A 
MANURE. 
BY JOHN HUGHES, F.L C, 
Beprinted from the Journal of the Society of Chemical 
Iniustry, 30 April. 1901. No. 1. Vol. XX.) 
■ - '''HE manufacture of superphos- 
phate in this country may 
be considered to have com- 
menced in 1842, when the late 
Sir John Bennett Lawes, F.K.S., 
obtained a patent for treating 
ground mineral phosphates with 
sulphuric acid. 
The chemical theory then enunciated may be briefly 
expressed, namely, that the agricultural value of 
phosphate manures depended upon the extent to which 
the phosphoric acid they contained was rendered 
soluble in water through the aid of sulphuric acid. 
It was contended that this solubility in water insured 
the most complete diffusion through the soil that 
could possiblj be obtained, and this theory in itself is 
still regarded as correct. 
At first the treatment of ground coprolites with 
commercial sulphuric acid was carried on in a cautious 
manner ; only a portion of the phosphates, amounting 
perhaps to 20 per cent., was converted into what was 
known as soluble phosphates ; and frequently as much 
as 8 to 10 per cent, was still left as undissolved phos- 
Tha manure so produced was in an excellent dry 
condition. Indeed in those days complaints respect- 
ing damp condition were of rare occurrence. 
When acid, however, became cheiper, as the result 
of improved manufacture, and as competition increased, 
the utmost amount of soluble phosphate was got out 
of the manure, so that only 2 or 3 per cent, of phos- 
phate was left in a condition not soluble in water. 
Superphosphates then became damper and more 
acid, so that complaints respecting the condition were 
of frequent occurrence, because the farmer could not 
obtain uniform distribution from the manure clogging 
in the drill. 
Superphosphate when first introduced was chiefly 
applied as a manure for root crops, such as turnips and 
swedes, which were usually raised on good arable 
land containing a fair quantity of lime. 
Indeed as early as 1863 the late Dr. Augustus 
Voelcker, writing in the journal of the Royal Agri- 
cultural Society upon " Phosphatic Manures for Root 
Crops," writes : — 
" Superphosphates of lime applied to root crops has 
a different practical effect on different soils. 
" The more rapidly and completely the soluble phos- 
phate in commercial superphosphate and turnip 
manures is precipitated and rendered insoluble in the 
soil, the more energetic will be its effect upon the 
turnip crop. 
'' Purely mineral superphosphates fail to produce 
good turnip crops on light sandy soils. 
" Bone dust partially dissolved by acid is a better 
manure on light soil than a purely mineral, super- 
phosphate, 
" It has indeed been observed that the exclusive 
use of superphosphate, however beneficial it maybe 
in the majority of instances, has in some soils led to 
complete or partial failure or tha presence of 
disease in the turnip crop. 
"The reconversion of soluble into insoluble phos- 
phate perhaps may appear undesirable, but in reality 
it is not only beneficial, but absolutely necessary to 
healthy and luxuriant development both of tur- 
nips and of all other crops to which superphosphate 
js applied. 
" No acid combination as such can enter into 
plants without doing them serious damage; even 
free vegetable acids, such as humic and ulmic acids, 
