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of lime : now, however I believe suitable forms have been found closer 

 at hand. To get over the difficulty of obtaining chalk possessing the 

 necessary fine powdery character and the requisite purity, the use of 

 alaked lime suggests itself, this latter substance occurs in the form of a 

 fine powder, easily mixed with water and can be obtained in a state of 

 great purity ; in default of other pure sources of supply, coral may be 

 used, this will yield lime containing a negligable amount of impurity. 

 Analyses af several kinds of coral showed Carbonate of lime 95 37 to 

 98'07 per cent. Phosphate of lime '32 to '84 per cent.. Organic matter 

 1-93 to 3-79 per cent. 



Should slaked lime be used, care must be taken not to neutralise the 

 juice completely or impurities will be precipitated with the citrate, and 

 these impurities will interfere with the subsequent manipulation and 

 the production of citric acid : where slaked lime has to be employed it 

 would appear desirable to complete the neutralisation with chalk, using 

 the lime only for the neutralisation of the greater part of the acid. 



In producing citrate of lime, the lime or lemon juice is placed in a 

 suitable mixing vessel, large enough to prevent loss from overflow 

 from the foaming effervescence which takes place when chalk is added. 

 A sufficient quantity of chalk is made into a cream with water and the 

 mixture poured cautiously into the juice with constant stirring, pro- 

 ceeding cautiously as the acid is neutralised. There is some difficulty 

 in ascertaining when the exact point of neutralisation is arrived at, for 

 in the presence of certain impurities, notably phosphate of iron, the juice 

 remains acid although an excess of chalk may have been added. To 

 ascertain how much chalk is to be used it is best to proceed as follows, 

 — when the greater part of the chalk has been added, the mixture is 

 well stirred and the effervescence is allowed to subside, a small quantity 

 is then taken out and tested by the addition of a little of the mixture 

 of chalk and water ; if this produces an effervescense more chalk must 

 be added to the main quantity, proceeding cautiously and testing at in- 

 tervals, until no effervescence is produced. A further test is now 

 made, — a little of the mixture is withdrawn and heated, as soon as bub- 

 bles of gas cease to be given off, a few drops of acid, fresh lime juice 

 will answer, are added, this will produce a slight effervesence if chalk 

 has been added in right amount, and a brisk effervesence if too much 

 has been used. In the latter case, more juice must be added to the 

 mixture and the process of testing repeated. 



Having added the correct quantity of chalk it is desirable to heat 

 the mixture for a few minutes nearly to boiling point, actual boiling is 

 not necessary, this causes the citrate of lime to become crystalline and 

 to subside rapidly in a condition in which it is easily manipulated. 



In the earlier attempts to prepare this substance the heating at this 

 stage was omitted, the juice was neutralised and the citrate of lime was 

 separated from the cold liquor and dried. In consequence of this me- 

 thod of working the finished citrate contained many impurities, it dried 

 in the form of hard lumps or of a powder fnll of hard knots so that 

 grinding had to be suggested, it was difficult to powder and when 

 thrown into water it was wetted with difficulty so that the manufacturer 

 had difficulty in acting upon it with sulphuric acid when converting it 

 into citric acid. Owing to the presence of impurities the citrate often 



