THE CONCENTRATION OF THE SYRUP TO MASSECUITE. 



destruction of the vacuum, causing a rise in temperature, would effect the 

 solution of small crystals, which would be recovered on subsequent cooling in 

 motion. 



The importance of a well distributed feed of the syrup is recognized in the 

 Delavierre patent. In this arrangement a pipe is fixed around the saucer of 

 the pan ; this pipe communicates with the interior of the pan by a number 

 of valves, the aperture of which is about one- sixteenth of an inch ; the syrup 

 is pumped into a receiver connected with the pipe on which are these valves ; 

 the syrup is injected into the pan through these valves in a number of fine jets 

 whereby an extremely uniform distribution is obtained ; with this device it is 

 easy to obtain with but little attention a continuous feed of syrup into the pan. 



Supersatliration. A. saturated solution of sugar or of any soluble 

 body is one that can neither dissolve more sugar nor yet precipitate the 

 dissolved body as long as the temperature and other conditions are maintained 

 constant ; in any case, if the conditions are altered either by removing water 

 or by lowering the temperature, the separation of the sugar is not instantaneous 

 and an unstable supersaturated condition results. If S be the solubility of 

 sugar in water in saturated solution, and S t be the solubility in a super- 

 saturated solution, Claassen terms the ratio ~ the coefficient of supersaturation, 

 and on this idea he has based a system of methodical pan boiling. 



Before the granulation of the syrup in the pan can be obtained, a super- 

 saturated solution must be formed, and the higher the coefficient of supersatura- 

 tion at the granulation, the larger will be the number of crystals deposited, 

 and consequently the smaller will be the size of the crystals on the completion 

 of the strike ; referring to beet sugar conditions, Claassen states that a 

 coefficient of supersaturation of at least 1*2 is necessary, and that the average 

 is 1'5 to 1'6; if a lower coefficient than 1*2 is used there is risk of redissolving 

 the crystals on the addition of the next charge of syrup. During the process 

 of growing the grain it is necessary that a uniform supersaturation be main- 

 tained throughout the entire mass, as otherwise the crystals will grow unevenly, 

 and if a too high supersaturation obtain in any part of the pan a fresh crop of 

 crystals (false grain) may form. The evaporation is greatest in those parts 

 next the coils, and least in those parts next the inlet of cold syrup ; hence, to 

 obtain uniformity, the circulation of the mass and the distribution of the syrup 

 must be controlled. Devices affecting these points have already been discussed, 

 and it is well that the syrup should enter the pan at the least at a temperature 

 not lower than that there prevailing. As a guide at this period, Claassen states 

 that with a continuous feed of syrup a coefficient of supersaturation of I'l 

 should be maintained, and that with an intermittent feed the supply of syrup 

 should be cut off when the coefficient falls to 1, and opened when it rises to- 

 1-2 ; finally, at the end of the strike the coefficient should be raised to 1-3. 



351 



