THE DETERMINATION OF CANE SUGAR 527 



against decinormal alkali ; 10 c.c. of the latter are equivalent to 56 c.c. 

 of the acid, which, when exactly made up, neutralizes volume for volume 

 a solution containing 0-05 grm. lime per 1,000 c.c. ; the indicator emploved 

 is phenolphthalein, which is placed in the stock of standard acid. The tube, 

 Fig. 342, is filled to the zero mark, and the standard acid added ; as long as 

 lime is in excess, the juice remains red, becoming finally colourless when the 

 Hme is neutralized. Each ten divisions in the tube correspond too-i grm. 

 -^me per 1,000 c.c. For juice of the second saturation a weaker acid, only 

 <^.ne-fifth the strength of the above, is used. 



The determination of the total lime in the juice is performed by the usual 

 methods ; 100 c.c. juice are heated to boiling, treated with ammonia in 

 excess, and filtered, if necessary ; the lime is precipitated by ammonium 

 oxalate from the hot solution, boiled for two hours, filtered, washed, dried, 

 and weighed as carbonate or sulphate. 



The alkalinity of a juice is in part due to caustic soda and potash set 

 free by the action of lime on the salts of the former present in the juice. 

 When it is wished to determine the alkalinity due to lime and to soda and 

 potash, Pellet's method may be used : i. Determine the total alkalinity 

 by titration with sulphuric acid, using litmus as an indicator and making 

 the titration at the boiling point. 2. To a volume of the juice add an equal 

 bulk of alcohol, which will precipitate the lime as an insoluble saccharate ; 

 filter, and in an integral part of the filtrate determine the alkalinitv ; the 

 latter is due to free caustic potash and soda, but is expressed as lime for 

 purposes of convenience : by determining the total lime, the combined 

 lime can be likewise obtained. 



Sulphiied Juices. — In the control of sulphitation processes, the sulphurous 

 acid free and combined is often determined as such. The means adopted 

 is the titration of the material with a standard solution of iodine in potassium 

 iodide. Starch is used as indicator, an intense blue colour appearing with 

 the presence of free iodine. This analysis does not give acidity, but shows 

 free and combined sulphurous acid. One-hundredth normal iodine contains 

 1*27 gram iodine per 1,000 c.c, and one c.c. is equivalent to 0-32 mgrm. 

 of sulphur dioxide. 



The Analysis of Limestone and Lime. — It is not general for sugar factories 

 to prepare their own lime, but in the carbonation process it is necessar}-, and 

 where a supph' of limestone is abundant, as in Mauritius and Barbados, 

 it is cheaper to burn lime than to import. The choice of limestone is im- 

 portant, and it is advisable also to keep a check on the composition of the 

 purchased lime. 



Moisture. — Dry 1-2 grms. to constant weight. 



Sand, Insoluble and Organic Matter. — Dissolve about i grm. in h3'dro- 

 chloric acid, filter through a tared filter paper, wash and dry at 100^ C, 

 weigh, giving the weight of sand, etc., ignite and weigh obtaining the sand, 

 the difference of the two weights giving the organic matter. 



Soluble Silica. — Evaporate to complete dr^Tiess the filtrate from the 

 determination of the sand, etc. ; moisten the residue and again evaporate 

 to dryness, keeping the residue at a temperature of 120° C. for an hour 

 after the residue is apparenth^ dry ; take up with hot water, filter and wash 

 till free of chlorides ; dry, ignite, and weigh the residue as Si02. 



