SUGAR BOILING AND CRYSTALLIZATION-IN-MOTION 389 



ELEVATION OF THE BOILING POINT OF SUGAR SOLUTIONS (CLAASSEN). 



FIG. 236 



The actual determination of the elevation is made with an instrument 



devised in 1898 by Curin. 2 This instrument was developed by Claassen, 

 who added to it scales whereby from observation of the 

 vacuum and temperature the degree Brix referred to a sugar 

 standard can at once be found. 



The brasmoscope consists merely of an accurate ther- 

 mometer (the bulb of which is immersed in the boiling mass 

 in the pan and placed so as not to be affected by local causes 

 such as the proximity of a steam coil) and an accurate baro- 

 meter pressure gauge, the ordinary aneroid gauges not being 

 of sufficient accuracy. 



The form of barometer gauge usually found is a syphon 

 barometer, Fig. 236 ; this consists of a U-tube closed at the 

 end A and open at the end B ; the tube is filled with mercury, 

 and when held in a vertical position the difference of level 

 between the mercury in the two 

 limbs will give the pressure of the 

 atmosphere in inches of mercury. 

 This U-tube is fixed on a board 



carrying a scale and is adjusted so that the level 



of mercury in the long limb is at zero mark 



when under atmospheric pressure. If the open 



end be now attached to a vessel in which there 



is a reduced pressure, the mercury in the long 



limb will fall until the difference in level is that 



due to the pressure in the vessel connected to 



the short limb. The scale is so graduated as to 



give directly inches of vacuum in the vessel to 



which the short limb is attached. This instru- 

 ment is not too convenient, as the gauge has 



always to be set at the zero mark and as a fall 



of pressure of, say, I inch in the vessel where the 



pressure is being measured only causes the level 



of the mercury in the long limb to fall half an 



inch, the level of the mercury in the short limb 



at the same time rising half an inch. The writer has therefore devised the 



pressure gauge described below, Fig. 237. N 



FIG. 237 



