946 



SUGAR 



and a steam-jacket The vapour arising from the boiling solution of sugar is con- 

 densed by an injection of cold -water, the arrangement of which, and the maintenance 

 of a vacuum, closely resemble the condenser, injection, and air-pump of an ordinary 

 condensing steam-engine. 



Fig. 1934 shows the structure of a single vacuum-pan. The horizontal diameter 

 of the copper spheroid cc, is from 7 to 10 feet; the depth of the under hemisphere A, 

 is at least 2 feet from the level of the flange ; and the height of the dome-cover is 

 from 3 to 5 feet. The two hemispheres (of which the inferior one is double, or has 

 a steam-jacket), are put together by bolts and screws, to preserve the joints tight 

 against atmospheric pressure. 



The steam enters through the valve F, traversing the copper coil D, and filling the 

 steam-jacket, the condensed water issuing from a small pipe below, c represents the 

 dome of the vacuum-pan, the vapour from which, passing in the direction of N, 

 allows any particles of sugar carried over by the violence of the ebullition to be 

 deposited in the receiver, M. 



1034 



The vapour is condensed by jets of cold water issuing from a perforated pipe, and 

 the water, uncondensed vapour, and air, are removed by the action of a powerful air- 

 pump. L is the measure cistern, from which the successive charges are admitted 

 into the pan; i and K represent respectively a thermometer and a barometer : the 

 former being required to indicate the temperature of the boiling syrup, and the latter 

 the diminished atmospheric pressure within the pan. p is the discharge cock ; and n 

 the proof-stick, is an apparatus inserted air-tight into the cover of the vacuum-p;i!!. 

 and which dips down into the syrup, serving to take out a sample of it, without allowing 

 air to enter. It is shown in detail, in fig. 1939, which represents a cylindrical rod, 

 capable of being screwed air-tight into the pan in an oblique direction downwards. 

 The upper or exterior end is open ; the under, which dips into the syrup is closed, 

 and has 'on one side a slit a (figs. 1936, 1939), or notch, about in. wide. In this 

 external tube, there is another shorter tube b, capable of moving round it, through an 

 arc of 180. An opening upon the under end e, corresponds with the slit in the 

 outer tube, so that both may be made to coincide,^. 1934, A. A plug d, is put in 

 the interior tube, but so as not to shut it entirely. Upon the upper end there is a 

 projection or pin, which catches in a slit of the inner tube, by which this may bo 

 turned round at pleasure. In the lower end of the plug there is a hole e, which can 

 be placed in communication with the lateral openings in both tubes. Hence it is 



