te. S, 1901.] ^HE TROPICAL ACTRIGULTUrJST. 
181 
fcgo. One after another the authorities refuse to 
have anything to do with it, and he got a wigging 
because he suggested that it would have a manurial 
value. Tbe fact was that basic slag had become a 
very useful manure both in England ai.d on the 
continent. Dr. Voelcker a&ked, Why should not a 
farmer take his superphosphate and add lime to 
himself 'i Ue might, but he would not do it so well 
as a mannfacturer. Bat would one gain anything by 
taking superphosphate and adding lime to it ? He 
ventured to think one would, wherever an alkaline 
phosphate would be useful ; also because the ordinary 
acid superphosphate was, after all, not on the 
average in a very tine condition ; it would hardly 
go through a 10-hole sieve. But after mixing it with 
lime, one could send the mixture through a 30- or 
40- hole sieve. Taking the relative surfaces which 
the increased fineness yielded, one would find very 
great advantage by that superior subdivision, so 
that in many cases it would be found quite equal 
to the ordinary acid superphosphate, even where 
this article was successfully used. One advantage 
it had was that it was more readily distributed, 
and that it would allow of the simultaneous use of 
nitrate of soda, and where it was desirable to put 
them together that could be done. One point had 
not been touched upon which he thought the 
makers of this article would find desirable, namely, 
the degree of hydration of the lime to be added 
to the superphosphate. If they took quicklime and 
added it after grinding, they would get tricalcio 
phosphate, but if they hydrated it with as much 
water as it would carry, they would get a finely 
divided powder; this, added as BIr. Hughes directed, 
was one that produced a hydrated mono- or dicalcic 
phosphate which WrfS far more soluble. Therefore 
he suggested that they should take a lime that 
would take two-thirds of its weight of water, and 
hydrate it at that rate ; this would break down 
readily. If they took lime and water in those 
proportions, namely, one of lime (CaO) to two of 
water (H2O), when added to the superphosphate 
it would form a body which would be more soluble 
than with a greater number of molecules of lime 
(GaO) only. He believed it would prove to be more 
valuable as a manure than even basic slag bad been. 
Dr. B 'RNARD Dyer said that it was interesting 
to think that the author of the piper before them, 
Dr Voelker, Mr Lloyd, Mr. Ruffle, and himself 
were all old' pupils of the same grand old master, 
and he could not help thinking that most ot what 
was best in the knowledge af all of them had been 
derived from him. For really the quotations tl^at 
Mr, Hughes had made from the early paper by 
Dr.' Voelcker went to the heart of this matter. 
The great value of a superphosphate lay in its 
diffusibility, and the utmost value to be derived 
from this quality could only be realised in those 
soils which had a satisfactory proportion of car- 
bonate ot lime. He had tried to persuade farmers 
to use more discrimination as to the kind of phos- 
phatic manure they employed, and bad laid it 
down as a rule for guidance that, if they had a 
soil that would effervesce when hydrochloric acid 
was poured on it, an acid or dissolved phosphatic 
manure was tbe most valuable one they could use ; 
but that, when no such effervescence took place, 
they should have resource to some other form, 
such as bonemeal, guano, or basic slag. There 
was another material which was m.nufactured 
to a large extent some years ago, and was referred 
to by Dr. Voelcker, mamely, precipitated phosphate. 
Large quantities of it were made on the Rhine by 
precipitating a solution of phosphoric acid with 
lime, and it was suitable for use on soils which 
were deficient in lime. What Mr. Hughes made 
was precipitated phosphate. He felt inclined to quarrel 
with his term " basic. " He really made a preci- 
pitated phosphate, and he probably made it more 
cheaply by this "dry" process than it could be 
Bjade by the "wet" methocl of precipitation. But 
the manufacture of precipitated phosphate by the 
" wet " process had almost entirely disappeared 
since the efficacy of basic slag had been recognised, 
and basic slag hud quite taken its place. That 
fact was presumably due to questions of cost. The 
question now was whether it was more eco omical 
to dissolve phosphate by the process of '''r. Huahes, 
and then use lime te neutralise it. He took it 
that the uuit price of the phosphoric acid in this 
material would be higher than in some other forma 
of manure ; and they had yet to learn whether it 
was 80 much more useful as to waraut that higher 
price. Following tbe teaching of Dr. Voelcker, he 
had recomended farmers having soils poor in lime 
to buy superphosphate and bone-meal, and make 
a compost of it and also neutralise it. It occuri-ed 
to him that it might possibly be more economical 
to use finely ground phosphate itself instead of 
lime. One would thus be retaining in an available 
form all the phosphate already dissolved, and the 
free phosphoric acid which existed in the phosphate 
would react on the frosh quantity nnd make some of 
thit available, as well as bein^ itself converted into 
the non-acid form. What Mr. Llyod had said with 
regard to farmers being reluctant to use lime was 
quite true. He did not think, however, it was due 
to obstinacy, but rather to poverty ; for to lime 
soil in some districts was very expensive, and ia 
the present time the farmer had to look at every 
source of expense. He had no doubt that Mr. Hughes' 
mixture would be a very useful and valuable 
manure ; his only doubt was as to its economy. 
He had shown it to be more soluble than slag 
phosphate in such weak solutions of citric acid aa 
he had taken ; but he feared th.it, if he took acids 
of such strength as were used on the continent, 
those great differences would disHppe ^r. As to the 
doubt which Dr. Voelcker had thrown on the valid- 
ity of Mr, Hughes' patent, he would not like to 
express an opinion. Patent law was very compli- 
cated, and there was no knowing what the result 
of litigation on such a subject might be. He should 
think the case would go right up to the House of 
Lords and that a great many experts would be 
found on each side of the question. 
Mr. A G. Blox.\m presumed that the 27 7 soluble 
in Mr. Hughes' table represented that percentage 
of tricalcium phosphate rendered soluble. Mr. 
Hughes treaed the same sample of superpboa- 
phate with lime, and found 91 per cent, soluble 
in citric acid. Did he mean to say that the calcium 
sulphate and all dissolved up ? If so, the comparison 
appeared to the speaker to be valueless. Then, with 
regard to that same determination, the sample 
mixed with lime was washed with water and citric 
acid, the soluble mattter weighed, and the residue 
ignited and weighed; the whole then added up to 
100. Was that so? 
Mr. Hughes replied that it was so. 
Mr. D. A. Lotus said it might interest the meet- 
ing to hear the views of one who had not bad the 
advantage of being in the late Dr. Voelcker'a 
laboratory. Some years ago, however, he had 
been in the laboratory at Rotharasted and he 
remembered the position taken up by Dr. Augustus 
Voelcker, Sir John Lowes, and Sir Henry Gilbert 
in connection with basic slag. They all per- 
sistently set their faces against it, considered it 
absolutely valueless, and even refused for some 
time to experiment with it. It was thought to 
contain deleterious ingredients, and the phosphoric 
acid to be in an unsuitable condition, and that it 
could be valuable as a plant food seemed to them 
an impossibility. Ho remembered discussing the sub- 
ject with Dr. John Voelcker some years ago, who, 
too, considered it quite worthless. In course of time, 
however, all these gentlemen came to recognise basic 
slag as an important manurial agent. That f"ob 
showed the position that some of our dear old 
agricnlturial friends were liable to take up when 
anything novel was presented to them, althoufjh 
