36 



THE PRODUCTION OF MAPLE SIRUP AND SUGAR. 



point on the scale where the instrument comes to rest is considered 

 the density. It will be noted that the surface of the liquid is curved 

 up at the points of contact with the metal cylinder, and also with the 

 hydrometer. The correct reading of the instrument is on a line with 

 the surface of the liquid as shown in the cut and not at the upper 

 edge of the curved portion. The temperature at which Baume hy- 

 drometers are standardized is 60 F., unless it is otherwise marked 

 on the stem of the hydrometer, so for correct readings the sirup 

 should be cooled to that temperature. A sirup of standard density 

 has a Baume reading of 35.6, but if measuring the density of the 

 boiling liquid by drawing some out into a cylinder the density will 

 be somewhere about 32 to 34 and on cooling 35.6 to 36. This is 

 readily understood when one considers that the zero of the hydrom- 

 eter is at the upper end and the 50 at the lower end. On heating a 

 liquid, there is an expansion and the liquid is lighter, so the hydrom- 

 eter sinks farther down than on cooling, when there is a contraction 

 of the liquid. The accuracy of these glass hydrometers is very much 

 affected by using them in hot liquids, hence it is not good practice 

 to use the accurate instruments in the hot sirup. 



The following table shows the solid content and the water content 

 for different degrees Baume. These figures are only approximate. 

 A gallon of the finished sirup should be weighed to give accurate 

 results. 



Dry substance and water corresponding to each degree Baume. 



Taken at 60 F. 



It is not to be understood that a degree Baume corresponds to 1.7 

 per cent of sugar, for the hydrometer measures other dissolved solids 

 also. 



In order to determine relatively the number of degrees Baume of 

 the cooled sirup when the reading is made with the hydrometer at 



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