Superphosphate of Lime. 
147 
bones prepared separately with the two acids, and afterwards 
mixed together, might be more productive than bones prepared 
with either acid alone. 
The proportion of sulphuric acid most desirable to employ is 
a very important point, inasmuch as it has been shown that sul- 
phuric acid alone, or mixed with water, possesses very little fer- 
tilizing powers. This probably is owing to the circumstance of 
the soil generally containing a sufficiency of this element, and to 
the fact that phosphoric acid is so extremely essential, particularly 
in the early stages of the growth of the plant, that it will not 
prosper without it, whatever we may otherwise employ as manure. 
A neighbouring agriculturist during the last year tried to raise 
a crop of turnips with a good dressing of salt and soot, which 
contain no phosphoric acid though plenty of ammonia and other 
fertilizing ingredients, but the result was a total failure. In a 
garden experiment, I may here observe, I found sulphuric acid 
and water succeed as well as bones in raising turnips, but the 
soil no doubt contained phosphoric acid, as well as alkalis, on 
which the acid could act favourably. 
Before we authoritatively pronounce on the quantity of acid 
necessary to be mixed with the bones, it will be better to inquire 
into the nature and properties of the substances we propose 
mixing together. 
Sulphuric acid, or oil of vitriol, as it is more frequently termed, 
consists of the union of two parts by weight of sulphur with three 
of oxygen gas, and its strength depends on its purity and freedom 
from water, for which it has a remarkable affinity, so much so 
that if exposed to the air it will quickly absorb water from the 
atmosphere. Its relative weakness, therefore, is owing to the 
quantity of water mixed with it. In speaking of sulphuric acid, 
I must be understood to mean the acid in its concentrated state, 
possessing a specific gravity of from 18'45 to 18"50. And it 
should be borne in mind, in purchasing the acid, that 50 lbs. of 
the above is at least equal to 60 lbs. of the specific gravity of 
17 14, and therefore if the weaker acid is used, its quantity must 
be increased in proportion to the diminution of its strength. 
On applying the vitriolized bone to the tongue, we find that it 
tastes both sour and sweet. The sourness arises probably from 
the phosphoric acid, and the sweetness from the gelatine sugar 
which is formed by the action of the acid on the gelatine, con- 
verting a substance very difficult of decomposition into one readily- 
soluble, and which can be easily absorbed by plants. When 
concentrated acid is mixed with a quarter of its weight of water, 
the temperature of the mixture is raised to 300°, and boils away 
at a great rate. The action of this heat on the animal part of 
the bones renders it of a dark colour ; but if a small quantity of 
L 2 
