THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[May 20, 1871. 
£31 
or to force out certain other matters with the juice 
which are prejudicial to it. This uniformity of pressure, 
in consequence of the variability in the size of the canes 
and the knots and rind being harder than the other 
parts, is practically impossible under the present method, 
and thus a quantity of green wax, chlorophyll and other 
objectionable matters is expressed from the knots and 
the rind which should have escaped pressure altogether. 
The presence of the fragments of cane and of the small 
pieces of cellular tissue in the j uice greatly increases its 
tendency to fermentation and impedes the process of 
■defecation. Notwithstanding many improvements in¬ 
troduced into the construction of modern sugar mills, 
the amount of juice obtained by the best of them only 
averages about 70 per cent, of the weight of the cane. 
As the theoretical quantity of juice in the cane is 90 
per cent., there is about 20 per cent, of juice still left in 
■the cane after undergoing the process of crushing. 
If the results of pressure, as applied to beetroot and to 
cane be considered, the proportion of unexpressed juice 
in the beetroot, amounting to 9 per cent., compares 
favourably w T ith the 20 per cent, left in the cane. But 
the placing of the beetroot pulp into bags, and the 
proper building up of the piles of bags in the hydraulic 
press, are operations which take up much time and re¬ 
quire considerable skill to perform well. The expense 
of washing and mending the bags also forms a serious 
item in the cost. To obviate these disadvantages several 
methods have been invented. 
The first of these in chronological order was designed 
By M. Schutzenbach for the extraction of the juice by 
the means of centrifugal force. The beetroot pulp i 3 
placed in a cylindrical sieve or perforated drum, which 
is made to revolve on a vertical spindle at the rate of 
1000 or 1200 revolutions a minute, and is enclosed in an 
outer cylindrical casing. The action of centrifugal force, 
corresponding to the velocity of the rotation, effects a 
rapid displacement of the juice, while the solid portion 
<of the pulp is retained in the cylinder. A quantity of 
-water, amounting to about 30 or 40 per cent, of the 
weight of the pulp, is injected into the turbine, in finely- 
divided streams, during the operation, for the purpose of 
assisting the displacement of the juice. By this method, 
under careful management and supervision, the yield of 
juice from the beet has reached 88 per cent., while, as 
compared with the hydraulic press system, the manual 
labour is greatly reduced, and the expense of the pulp 
hags is avoided altogether. The centrifugal system has, 
however, not gained ground on the Continent, principally 
from its success depending too much upon the skill and 
•care in the working of the turbine; the slightest variation 
in the quality or quantity of the pulp with which it is 
charged requiring a scientific readjustment of the quan¬ 
tity of water injected and of the speed of the revolu¬ 
tions. 
Another method, invented by the same "gentleman, 
consisted in the pulp undergoing a process of maceration. 
This was effected by causing water to pass succes¬ 
sively through a series of ten or twelve tanks charged 
with pulp, which -were placed so that the juice might 
drain off from one tank into the next until the last was 
reached. The process is very economical in the amount 
of labour required, and is capable of a good yield under 
careful management. 
But this invention is superseded by that of Herr 
Julius Robert, of Seelowitz, in Austria, one of the most 
eminent beetroot sugar manufacturers on the Continent, 
which is a process of diffusion, dispensing entirely with 
Ihe application of direct mechanical force, and based 
upon Graham s celebrated discovery of the osmotic pro¬ 
perties of organic cells. By it the saccharine matter is ex¬ 
tracted from the closed cells without bursting them open. 
The name of diffusion was given by Graham to a process 
which takes place when two liquids containing different 
bodies in solution are separated only by an organic 
.membrane; the liquids mutually exchange their soluble 
matters and gradually equalize their degree of concen¬ 
tration. There is, however, a great difference in the 
speed with which this exchange and equalization take 
place ; crystallizable bodies, such as sugar and salts, 
passing through the organic partition at a quicker rate 
than non-crystallizable, such as albumen and other ni¬ 
trogenous compounds. By this property, therefore, the 
unbroken cells of beetroot or cane immersed in water or 
weak saccharine solutions are capable of yielding part of 
their sugar and salts to the surrounding liquid. A slice 
of beetroot or sugar cane, containing 10 per cent, of 
sugar in its juice, immersed in an equal weight of water, 
will gradually part with its saccharine contents until the 
juice in the cells and the water outside each contain 
5 per cent, of sugar. If a fresh slice, containing 10 per 
cent., be placed in this 5 per cent, solution of sugar, the 
resulting equalization will produce a solution of 7 ^ per 
cent. On the other hand, the partially-exhausted slice, 
containing o per cent, of sugar, will part with 2 j per 
cent, of it to a fresh supply of water. Thus, by a series 
of operations, bringing the pure water into contact first 
with nearly exhausted slices, and then passing the weak 
saccharine solutions over slices which have parted with 
a smaller proportion of their sugar, the solution pro¬ 
duced may be brought very nearly to the density of the 
natural juice of the plant; while the slices coming in 
contact successively with weaker and weaker saccharine 
solutions, and finally with pure water, give up near ly all 
their sugar and become completely exhausted. Another 
advantage resulting from this process is, that in conse¬ 
quence of the difference of speed between the diffusion 
of sugar and that of the nitrogenous compounds in a 
given time, which, if sufficient for the proper proportion 
of sugar and soluble salts to pass into the surrounding 
liquid, only a small portion of the nitrogenous com¬ 
pounds will be given up ; while the insoluble impurities 
are prevented entirely from leaving the cells of the plant 
and passing into the diffusion juice. Thus the juice pro¬ 
duced by the diffusion process is always purer and less 
liable to spontaneous decomposition or fermentation 
than that expressed by mechanical force. This process 
has been applied to beetroot and to sugar-cane with an 
equally complete and decided success. 
In practically carrying out this system, the beetroots 
are first washed, and then cut by machinery into slices 
of about 5 in. or f- in. in width and thickness, and of a 
length according to the size of the roots. They are then 
ready for placing in the diffusion battery. This consists 
of nine or ten cylindrical vessels, containing slices in 
different stages of exhaustion and juice of different de¬ 
grees of density. As each portion of the operation is 
completed, the solution is conveyed to the vessel contain¬ 
ing the slices with the next highest i>roportion of sugar. 
Thus in each vessel in turn the slices having the least 
sugar are brought into contact with fresh water, and are 
discharged from it with only about ^ per cent, of sugar; 
while at the other end of the process the rich solution 
which has passed successively through the other vessels 
is passed into that containing the fresh slices, and is dis¬ 
charged thence into the clarifying-pan. The exhausted 
slices are equally valuable as a food for cattle with tho 
pulp from the hydraulic press, but they hold a large sur¬ 
plus of water, which is a drawback when it is necessary 
to convey them from one place to another. This has been 
to some extent obviated by submitting them to the action 
of a hydraulic press, which removes the water without to 
any great extent expelling the elements of food. 
With the sugar-cane the process is very similar, and 
it has been successfully carried out by a company in 
Madras. The juice so procured is very pure ; it has a 
bright yellow colour, and gives off but little scum in 
the clarifier. When the cane is perfectly ripe and in 
good condition, the diffusion juice requires no filtration 
through animal charcoal, and may be passed at once into 
the evaporators and vacuum pans, producing good high- 
class raw sugar. The diffusion juice, however, contains 
