MELSEN’S PROCESS 159 
no change of color will be produced in this way; but if 
there should be, it will be but temporary, and of no con- 
sequence. The dark coloring matter being a precipitate 
which is merely mechanically suspended, and not dissolved 
in the liquid, is thrown up with the other impurities when 
heat is applied, and it is removed with the scum. 
A much more serious disadvantage is the extreme de- 
gree of care that is necessary—much more than would 
ordinarily be exercised —in apportioning the chemical 
agents used to the exact effect designed to be produced. 
Three times—once before each filtration —the juice must 
be treated with lime or tannin; these must be in due pro- 
portion to each other, or to the variable amount of im- 
purities in the juice with which they combine. It is true 
that the bad consequences of a failure to exercise proper 
care in the use of defecating agents is not peculiar to this 
process, but belongs to all others in which such substances 
are used. Yet, here, the lapse of an extended interval 
between each application imposes a tax upon the memory 
of the operator whose attention is divided between this and 
other matters, and the liability to commit errors through 
forgetfulness is in this case much greater than in those in 
which the required additions are made in immediate sue- 
cession. 
The practical difficulties attendant upon the successive 
filtrations of the cold juice are the chief impediments 
known to the general adoption of this method, and we are 
compelled to abandon it with regret, since in other respects 
its results are very satisfactory. 
MELSEN’S METHOD, 
which has acquired considerable celebrity in Europe as 
applied in the beet-sugar manufacture, and also in Louis- 
