66 SUGAR 



operation, would be fatal. Hence the introduction of 

 the vacuum pan, where the thick juice can be boiled 

 violently at a perfectly safe temperature. x It is, if 

 we look at its original form of fifty years ago, a slightly 

 flattened sphere of copper provided inside at the lower 

 part with a coil of steam pipe, and also with a steam 

 jacket. An air pump creates a partial vacuum, and a 

 condenser, through which the steam from the boiling 

 juice passes on its way to the air pump, by rapidly 

 condensing the vapour greatly helps to increase the 

 vacuum. The juice is always boiling more or less 

 violently, even when thick, and, therefore, throwing 

 off its vapour freely. This pan in its complete form 

 appeared about the year 1830, and about thirty years 

 afterwards began to be used in the tropics as a useful 

 adjunct to the preliminary evaporation of the thin 

 juice. The vacuum pan, in fact, finished the operation. 

 But it did more than this, it enabled the factory to 

 produce a more distinctly crystalline form of sugar 

 than the old muscovado kind, which comes from the 

 confused crystalline mass formed by the spontaneous 

 crystallization of the thickened juice when, on cooling, 

 it crystallizes of its own accord. But the use of the 

 vacuum pan did not become extensive for many years. 

 Mauritius and the French West Indian Islands were 

 the' first to use it on any considerable scale ; then came 

 Demerara, Berbice and Trinidad. Now it is used 

 everywhere, except in primitive countries. 



The vacuum pan puts the finishing touches to the 

 thickened juice, but a great deal of evaporating has 

 to be done before the juice arrives at that state. Another 



1 A solution of sugar must be heated above 212 F., the 

 boiling point of water, before it boils ; but in a partial vacuum 

 it boils violently at 160 F., and at even a lower temperature in 

 a more perfect vacuum. 



