98 



^The World's Commercial Products 



through one can see the whole syrupy contents, and the expert sugar-boiler can tell by their 

 appearance when the critical moment has arrived and the sugar is ready to crystallise. To 

 ascertain this with even greater precision, by means of an ingenious invention, the " proof 

 stick," small samples of the boiling Contents may be taken out from time to time without in 

 any way breaking the vacuum. The sample of syrup withdrawn is allowed to form a thin 

 sheet on a piece of glass, and from the appearance of this as it cools the condition of the contents 

 is judged. When ready to crystallise or "grain," the temperature is lowered suddenly, and 

 small sugar crystals are formed. These become more numerous, and when judged to be suffi- 

 ciently- numerous more syrup is added and the temperature raised again. Various modifica- 

 tions in treatment now follow according to whether a large or a small grained sugar is being 

 made. In any case very careful attention is required to obtain the pan full of crystals with 

 a minimum of liquor. When the ideal has been reached, a door at the bottom of the 

 pan is opened, the contents flow out, and we have only to separate the crystals from the 

 molasses. 



Separation of Sugar from Molasses. There are various methods by which this can be done, 

 but they have all given way to the common process of using centrifugal separators. 

 These consist essentially of cylindrical metal vessels which can be made to revolve 

 at a very high speed. The walls of the separators are pierced by a number of holes, 

 and on the inside there is a lining of very fine metal gauze, of sufficiently small 

 mesh to prevent sugar crystals passing through. The separators, which are open at 

 the top, are partly filled with the mixture of sugar crystals and molasses, and set rapidly 

 rotating. The centrifugal force causes all the contents to fly to the outside and remain, as it 



were, pressed against the 

 wire gauze. The crystals are 

 held there, but the liquid 

 molasses passes through, is 

 caught in a receiver, and 

 conducted away. One may 

 stand and watch the whole 

 operation, which is over in a 

 very few moments instead 

 of the weeks required by the 

 earlier methods. As soon as 

 the motion ceases, the crys- 

 tals collect at the bottom of 

 the separator, which can be 

 opened to allow them to drop 

 out, and they are ready to 

 be packed and exported 

 immediately. 



To get rid of the last 

 remaining molasses the crys- 

 tals can be washed whilst 

 the separator is revolving, 

 this not being necessary in 

 white beetroot red beetroot preparing a " moist " sugar. 



The left-hand member of each pair has been grown without, and the right-hand 

 member with, manure 



