SUGAR-CANE SIRUP MANUFACTURE 27 
The thermometer most suitable for the purpose is one protected 
by a substantial copper case and graduated from approximately 50° 
to 250° F. The bulb of such a thermometer should be very close 
to the bottom of the protecting copper case but not quite touching it. 
This design is necessary in order that the thermometer bulb may be 
entirely covered by the shallow layer of boiling sirup (three-fourths 
inch deep). ‘Thermometers with long stems and magnified wide- 
mercury columns that may be easily read at a reasonable distance 
are very convenient. Such thermometers may be kept continuously 
in the sirup, and serve accurately to indicate the point of final evap- 
oration, when the sirup should be allowed to run out of the evapo- 
rator. Even though the thermometer be used only to check the siru 
maker’s guess as to the proper density, it will prove very teeta 
Sirup which tests 38.5° to 39° Baumé (70.8° to 71.8° Brix) at atmos- 
pheric temperature, using a hydrometer, boils at 224° F’. (106.7° C.), 
sea level, at the time when it should be allowed to flow from the 
evaporator. In testing a sirup for its density in this manner it is 
well to determine the accuracy of the thermometer by placing it in 
boiling water and noting the boiling point. Using an accurate ther- 
mometer, water should boil at 212° H. (100° C.) at sea level, 211° F. 
(99.4° C.) at an altitude of 500 feet, and at 210° F. (98.9° C.) at an 
altitude of 1,000 feet. For every 500 feet above sea level, roughly 
speaking, the boiling point is lowered 1° F., so that when using an 
accurate thermometer at a point 500 feet above sea level finished 
sirup would boil at 223° F. (106.1° C.), and at 1,000 feet above sea 
level it would boil at 222° F. (105.5° C.). The sirup is finished at a 
temperature 12° to 13° F. higher than the boiling point of water. 
From the evaporator the finished sirup flows into a sirup trough 
or tank in the room partitioned off for canning or barreling the sirup 
(fig. 2). Complete directions for canning are given on pages 58 
to 60. 
Some sirup makers, when marketing in bulk, barrel the sirup hot 
as it comes from the evaporator. This is considered bad practice, 
because sirup at high temperature often causes the barrels to leak, 
and hot sirup in barrels cools so slowly that the color and flavor are 
frequently impaired. Moreover, sirup that contains an excessive 
quantity of suspended material should remain in the tank overnight, 
and sometimes even longer, until this material has settled to the 
bottom. Clear sirup may then be drawn off from the top and barreled 
and the layer of sediment, if it contains much sirup, may be returned 
to the juice for skimming in order to avoid loss of sirup. 
Some sirup makers experience more difficulty than others from 
having an excessive amount of sediment in their sirup, this depending 
as much on the type of soil on which the cane was grown, the variety 
of cane, and extraction obtained as upon the skill of the operator. 
Sedimentation is in general the most feasible procedure for removing 
this material from sirup, before either barreling or canning. Sirup 
that has settled overnight, however, should be reheated for canning 
to the proper canning temperature (p. 59). 
Filtration of sirup when boiling hot, using cloth strainers, through 
which the sirup will pass within a reasonable time, does not remove 
much of the sediment. Moreover, when it has cooled to atmospheric 
temperature, the sirup at final density can not be filtered efficiently 
by any known means. In deciding whether or not to allow the 
finished sirup to sediment, it should be remembered that sedimenta- 
