192 HOW TO TEST CANE JUICE. 
a foot in height (a large lamp chimney will answer the 
purpose), tie a piece of coarse canvas over one of its open 
ends, and pour in dry, fresh, well washed animal charcoal 
(such as is used in the filter of the evaporator), until it is 
about half full, pack it down closely, and then pour in a 
convenient portion of the clarified juice from the test jar, 
collect it as it passes through the filter, rejecting the first 
that passes through, or about one-fourth of the whole volume 
of the liquid, because it is below the average strength. 
When the filtration is complete, return the remainder of 
the liquor to the filter, and filter a second time. If cane 
sugar only is present, the specific gravity bottle or hydrom- 
eter will give its per cent. in the filtered juice. Any excess 
of lead is retained by the boneblack, and separated en- 
tirely from the liquid. 
It remains to ascertain the relative proportions of the 
grape and cane sugars in the solution. Of the different 
methods that may-be employed for this purpose, but one 
can be recommended to those unprovided with chemical 
apparatus or unskilled in their use. This method consists 
simply in evaporating, in a shallow vessel, a weighed por- 
tion of the filtered juice, above mentioned, to the consistence 
of a thick syrup—the evaporation, at least during its last 
stages, being accomplished by means of the water-bath, or 
by exposing the evaporating dish to the heat of the steam 
escaping from a vessel of boiling water. The syrup should 
then be placed in a situation where it will be exposed to a 
uniform temperature of about 70°-80° F. If it has not 
crystallized after the lapse of a week, add to it a few drops 
enough to burn off all the organic matter. Weigh the protoxide of lead 
which remains, and its weight subtracted from the weight of the dried 
contents of the capsule already known, will give that of the organic 
matter with which it was combined. This method is sufficiently accurate 
for ordinary purposes. 
