CANE SUGAK. 



consumption sugars without danger of inversion." This reasoning was, however, 

 incorrect, for the invertive action is profoundly modified by the large amount 

 of neutral salt present in the experiment and which does not occur in the 

 boiling-house ; also the acids used in the boiling-house sulphurous and 

 phosphoric have in any case a much less pronounced action than sulphuric. 

 Actually, however, juices with an acidity due to phosphoric acid equal to a 

 maximum of 20 c.c. decinormal acid per 100 c.c. of juice are worked in the 

 manufacture of consumption sugars. 



Indicators. By an indicator is meant a body which by a change of 

 colour indicates the end point of some chemical reaction, and in the sugar 

 house it is used to indicate the acidity or alkalinity of the juice. The two 

 indicators most extensively employed are litmus and phenolphthalein ; the 

 former is red in acid and blue in alkaline solution ; the latter, colourless and 

 crimson. A difference in the indication of these bodies with lime and in the 

 presence of sulphites has already been noted, and the question, which is the 

 most reliable indicator to use, is one which is constantly recurring. This is 

 really largely a question of the glucose content of the juice; phenolphthalein 

 does not give an alkaline reaction until there is present considerably more lime 

 than is required to give an alkaline reaction with litmus; if juices such as are 

 common in Demerara, containing from 1*5 per cent, to 2 per cent, of glucose 

 were limed till they gave an alkaline reaction with phenolphthalein, serious 

 trouble, due to the action of the lime on the glucose, would result ; juices 

 with less glucose will be able to take a larger amount of lime and obtain a 

 greater precipitation of non-sugar without injury. 



In saturating alkaline juices with sulphurous acid it must be remembered 

 that litmus reacts alkaline to acid sulphites and hence phenolphthalein is the 

 more suitable indicator. 



Phenolphthalein is exclusively used in the beet sugar industry, but con- 

 ditions are dissimilar and Pellet in particular has frequently insisted that 

 litmus is the most general cane sugar indicator. 



An indicator of some little use is a reagent consisting of equal parts of 

 methyl orange and rosolic acid in alcoholic solution ; this reagent becomes a 

 peculiar port- wine red in the presence of bisulphites, but in general the colour 

 of cane products is so pronounced as to mask the appearance of this colour. 

 The colouring matter of cane juice itself forms an indicator of no inconsiderable 

 value, and is discussed above. 



Speaking generally, the appearance of the juice viewed in a tall glass 

 makes a valuable criterion, a clear hock-coloured juice with a rapidly 

 settling precipitate being the appearance to be looked for; the condition of the 

 press cake is also a guide, soft sloppy cakes being often the result of too little 

 lime. 



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