52 MAPLE-SAP SIRUP. 



lization is reduced by the presence of certain mineral salts and or- 

 ganic bodies and also by the invert sugar content. According to 

 Herzfeld, a saturated solution of pure sucrose at 15 C. contains 66.33 

 per cent of sugar and at 64 C., 74.98 per cent. Prinsen Geerligs states 

 that at 18 C. a saturated solution contains 67.1 per cent and at 

 27 C., 68.8 per cent of sucrose. The average maple sirup with 34.19 

 per cent of water contains 62.64 per cent of sucrose, and calculated to 

 a 32 per cent water basis this figure would be 64.73 per cent, a su- 

 crose content which would probably not be accompanied by crys- 

 tallization at ordinary spring or summer temperatures, but would 

 permit it at the lower temperature which is likely to exist at the 

 time the sirup is made and stored. The table shows that one sam- 

 ple with a 34 per cent water content had crystallized and the super- 

 natant liquid of some of the other fully crystallized sirups had a 

 water content of from 33 to 34 per cent, which would indicate that 

 68 per cent of dry substance was too high and that 65 per cent rep- 

 resented a more desirable composition. 



The makers of maple sirup have various methods of determining 

 the thickness or density of the sirup, some of which are scientific 

 and some are not. A special hydrometer and thermometer are some- 

 times employed and again the appearance of the boiling sirup, the 

 way in which the last drops fall from a spoon or cup, the quality and 

 strength of the sirup film, and the weight of a gallon are used as a 

 test of density. 



With a maximum content of 35 per cent water, the specific gravity 

 is 1.31989 at 17.5 C. or 35.6 Baume, and 1 gallon (231 cubic inches) 

 weighs 11 pounds. With a maximum content of 32 per cent water, 

 the specific gravity of such a sirup is 1.33836 at 17.5 C. or 37.1 

 Baume, and 1 gallon weighs 11.15 pounds or 11 pounds 2J ounces. 

 When determining the density of a sirup by actual weight the makers 

 fill the gallon can and weigh, allowing half a pound for the weight of 

 the can. Care should be taken to insure that the can holds an exact 

 gallon, that the weight of the empty can is obtained, and that the 

 sirup is cold or has a temperature of about 63 F. Only under these 

 conditions will the exact weight of a gallon of sirup be obtained. 

 When using the temperature of boiling as a means of determining 

 the water content or density, there are numerous points to be con- 

 sidered. The Vermont experiment station has found that a maple 

 sirup boiling at 219 F. a weighs 11 pounds to the gallon or contains 

 35 per cent of water, and one boiling at 221 F. weighs 11.2 pounds 

 and contains 32 per cent of water. These boiling temperatures are 

 for places at or near sea level. Every 500 feet of elevation lowers 

 the boiling point 1 F. approximately. To determine the density 



This figure is for a middle run sirup; with the first runs of sap a sirup of 65 per 

 cent of dry substance may boil at from 217 to 218 C. 



