MAPLE SIRUP PRODUCERS MANUAL 



73 



20 40 60 

 SUCROSE CONCENTRATION (PERCENT) 



Chart 15. — Curve showing the relation between the con- 

 centration of a sugar solution (sap) and the elevation of 

 its boiling point above the boiling point of water. 



elevation in boiling point. However, as the solu- 

 tion neai's the concentration of standard-den- 

 sity sirup, a change of only 2.5 percent in sugar 

 concentration (from 64.5° to 67° Brix) raises the 

 boiling point 1°. Hence, the boiling point method 

 of measuring sugar concentrations is ideally 

 suited to sirupmaking. 



Any Fahrenheit thermometer calibrated in 

 degree or half-degree intervals and with a 

 range that includes 225° F. can be used. For 

 greatest usefulness and accuracy, the distances 

 between degree lines should be as open as 

 possible and should be calibrated in one-fourth 

 degrees. 



Elevation of the boiling point as used hei'e 

 means the increase in temperature (° F.) of the 

 boiling point of the sugar solution above the 

 temperature of boiling pure water. It has noth- 

 ing to do with the specific temperatui'e 212° F. 

 except when the barometric pressure is 760 

 millimeters of merciu'v. Under actual condi- 



tions of sirupmaking, the barometric pressure 

 is seldom at 760 millimeters; therefore, it is best 

 not to associate the fixed value of 212° F. with 

 the boiling point of water. 



The recommended procedure is to establish 

 the temperature of boiling water on the day 

 and at the place sirup is being made. To do this, 

 merely heat water to boiling, insert the bulb of 

 a liquid stem thermometer or the stem of a dial 

 thermometer, and note the temperature while 

 the water is actually boiling. This is the true 

 temperature of boiling water for the barometric 

 pressure at that time and place. In practice, the 

 boiling sap in the sap pan can be used to 

 establish the temperature of boiling water 

 since, as was shown in chart 15, at low-solids 

 concentrations (up to 10° BrLx) there is little 

 elevation of the boiling point. The boiling tem- 

 perature of standard-density sirup is then 

 found by adding 7° to the temperature of the 

 boiling sap. 



It is of the greatest importance to redeter- 

 mine the temperature of boiling water (sap) at 

 least once and preferably several times each 

 day, especially if the barometer is changing. A 

 change in the weather usually indicates a 

 change in barometric pressure. The result of 

 failure to making frequent checks on the boiling 

 point of water is illustrated in the following 

 examples: 



On March 1, at Gouverneur, N.Y., the boiling 

 point of water was determined to be 210° F., 

 which established the boiling point of standard- 

 density sirup as 217°. On March 2, the producer 

 neglected to redetermine the boiling point of 

 water, assuming it to be unchanged, and con- 

 tinued to use 217" as the boiling point of sirup. 

 Actually, the barometric pressure had fallen, 

 which lowered the boiling point of water to 208° 

 and of standard-density sirup to 215°. The sir- 

 upmaker, by using the temperature of 217°, 

 was boiling his sirup 2° too high, and the sirup 

 contained 69.8 percent of solids instead of 65.8 

 percent (table 12). This high-density sirup re- 

 sulted in the production of fewer gallons of 

 sirup; and, in addition, the sirup crystallized in 

 storage, since it was above 67° Brix. 



If, on the other hand, the reverse had oc- 

 curred, the sirupmaker would have made sirup 

 with a boiling point 2° F. too low. This sirup 

 would contain only 59.7 percent of solids as 



