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- REPORT OF THE CHEMIST. 233 
it became a matter of the gravest importance to find a method of 
preventing this inversion without in any manner interfering with 
the other processes. On the suggestion of Professor Swenson a 
portion of freshly precipitated carbonate of lime was placed with 
the chips in each cell. In the case of soured cane this took up the 
acid which otherwise produced inversion. - In case no harmful acids 
were present this chalk was entirely inactive. Soured canes are not 
desirable to work under any circumstances, and should be rejected 
by the chemist and not allowed to enter the factory. So, also, delays 
on account of imperfect machinery are disastrous to profitable man- 
ufacturing and must be avoided. But for those who desire to ex- 
periment with deteriorated canes and untried cutting machines, the 
addition of the calcium carbonate provides against disastrous results 
which would otherwise be inevitable. 
CLARIFYING OR DEFECATING THE JUICE. 
‘ Immediately after it is drawn from the diffusion battery the juice 
is taken from the measuring tanks into the defecating tanks or pans. 
These are large, deep vessels, provided with copper steam coils in the 
bottom for the purpose of heating the juice. Sufficient milk of lime 
is added here to nearly or quite cnitedles the acids in the juice, the 
test being made with litmus paper. The juice is brought to the boil- 
ing point, and as much of the scum is removed as can be taken quickly. 
_ The scum is returned to the diffusion cells, and the juice is sent by a 
pump to the top of the building, where it is boiled and thoroughly 
skimmed. These skimmings are also returned to the diffusion cells. 
This method of disposing of the skimmings was suggested by Mr. 
Parkinson. It is better than the old’plan of throwing them away to 
decompose and create a strench aboutthe factory. Probably a better 
method would be to pass these skimmings through some sort of filter, 
or, perhaps better still, to filter the juice and avoid all skimming. 
After this last skimming the juice is ready to be boiled down to a 
thin sirup, in 
THE DOUBLE-EFFECT EVAPORATORS. 
These consist of two large closed pans provided within with steam 
_ pipes of copper, whereby the liquid is heated. They are also con- 
nected with each other and with pumps in such a way as to reduce 
the pressure in the first to about three-fifths and in the second to 
about one-fifth the normal atmospheric pressure. 
The juice boils rapidly inthe first at somewhat below the temper- 
ature of boiling water, and in the second at a still lower temperature. 
The exhaust steam from the engines is used for heating the first pan, 
and the vapor from the boiling juice in the first pan is hot enough to 
do all the boiling in the second, and is taken into the copper pipes cf 
the second for this purpose. In this way the evaporation is efiectec 
without so great expenditure of fuel as is necessary in open pans or 
in single-effect vacuum pans, and the deleterious influences of long- 
continued high temperature on the crystallizing powers of the sugar 
are avoided. 
From the double effects the sirup is stored in tanks ready to be 
taken into the strike-pan, where the sugar is crystallized. 
THE FIRST CHANCE TO PAUSE. 
At this point the juice has just reached a condition in which it will 
keep. From the moment the cane is cut in the fields until now every 
