CRYSTALLIZATION 67 



kind of vacuum apparatus has been invented as best 

 suited to that earlier stage. The French call it the 

 Triple-effet, and that is now its name. It is a very 

 ingenious and successful contrivance, and came from 

 France, at that time the leading country in the produc- 

 tion of beetroot sugar. The inventor, Rillieux, had 

 to pass many long years, as inventors generally do, 

 before he could procure a good trial of his new idea. 

 In the old days of open pans and the heat of a naked 

 fire the French manufacturers had to burn 400 kilo- 

 grammes of coal for every ton of roots worked. When 

 steam was substituted for fire heat, and the steam 

 engine was allowed to enter the factory to drive an 

 air pump for the vacuum pan, they managed to do the 

 work with 250 instead of 400 kilogrammes of coal to 

 the ton of roots. Rillieux proposed to make a further 

 great reduction in the cost of fuel by evaporating the 

 greater portion of the water in the thin juice in a double 

 or triple arrangement of pans, where the steam from 

 the boiling juice in the first should heat the second, and 

 so on. This began to be accomplished about the year 

 1852. By 1882 it was brought to a fair degree of per- 

 fection, and the amount of fuel per ton of roots was 

 reduced to 80 kilogrammes. 



The apparatus may be roughly described as consisting 

 of three vertical cylindrical vessels with dome-shaped 

 heads, ending in a wide neck which turns over and 

 downwards carrying the vapour to its next destination. 

 The lower part of each vessel is divided into three 

 parts, a small space at the bottom, then a much larger 

 space enclosed by two horizontal iron plates forming 

 the " steam drum," fitted with vertical copper pipes 

 permitting the juice, which enters at the small space 

 below it, to pass through the steam drum into the 

 large open space above it. The juice is allowed to rise 



