THE CONCENTRATION OF THE SYRUP TO MASSECUITE. 



This relation is the basis of an instrument known as a brasmoscope or 

 brixometer. 



The brasmoscope consists merely of an accurate thermometer (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 

 barometer pressure gauge, the ordinary aneroid gauges not being of sufficient 

 accuracy. 



The form of barometer gauge usually found is 

 a syphon barometer, Fig. 195] 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 atmo- 

 sphere 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 the 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 instrument is not too convenient, as 

 the gauge has always to be set at the zero mark and 

 as a full of pressure of, say, 1 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 devised the pressure gauge described below, 

 Fig. 196. 



A is a shallow receptacle of thick glass partly 

 filled with mercury ; on the upper side at B is a 



tubulure to be connected to the vapour space of the pan by stout rubber 

 tubing ; at C is the neck of the receptacle into which fits tightly the barometer 

 tubing D, graduated in tenths of an inch ; the receptacle A being filled with 

 mercury the graduated barometer tubing is then inserted in the neck of the 

 flask and mercury is sucked up above the level of the stop cock at E which is 

 then closed ; the mercury in A is then adjusted until its level is coincident 

 with the zero mark on D ; if then connection be made to the vapour space 

 of a vacuum apparatus by way of B, the height of the column of mercury 

 will directly measure the pressure in the pan. 



_8 



-14 



20 

 22 

 _24 

 _26 

 -28 

 _30 



FIG. 195. 



361 



