248 



is one important advantage that the carob has over other beans, namelv, 

 that it does not require threshing. In feeding horses it is usual to 

 break the pod into two or three pieces and to put it in the nose bag or 

 manger mix with bran. 



CITRIC ACID. 



Raw Material. 



Citric Acid is prepared from the fruit juice of three species of 

 Citrus — the lemon, bergamot, and lime ; the first of these is the prin- 

 cipal source of citric acid. Concentrated lemon juice is chiefly im- 

 ported from Sicily; a very little comes from Naples or Sorrento. Con- 

 centrated bergamot juice is prepared in Calabria and exported from 

 Messina. Concentrated lime juice is imported in small quantity from 

 Montserrat and Dominica. The lemon juice from Sicily is prepared 

 by pressing the inferior fruit, from which the rind has previously been 

 removed, for the manufacture of essence. The so-called "single" juice 

 is then boiled down till its ap. gr. equals 60° on the citrometer (sp. 

 gr. L 24) ; it then forms a dark brown, rather syrupy liquid. 



The total quantity of concentrated Sicilian and Italian juice im- 

 ported to England in 1887, was equivalent to rather more than 3,400 

 pipes of 108 gallons ; the amount used for the manufacture of citric 

 acid was probably equivalent to 3,200 pipes, of lime juice, about 2,000 

 puncheons of 110 gallons were imported in an unconcentrated condi- 

 tion, and used for the preparation of beverages. About 200 pipes of 

 concentrated lime juice were imported, and employed for the manufac- 

 ture of citric acid. 



Lemon juice has its greatest acidity early in the season (November). 

 The juice of the fine fruit, exported as lemons, has sp. gr. 1.03-1.04 ; 

 it contains free acid equal to 11-13 oz. of citric acid per gallon. The 

 inferior fruit pressed in Sicily yields a juice containing at the begin- 

 ning of the season about 9 oz. of free acid per gallon, and at the end of 

 the season a great deal less. 



There are other differences between the juice of fine lemon 

 pressed in England, and the Sicilian juice employed for the manufac- 

 ture of citric acid. The former contains very little combined organic 

 acid, only about 2.5 p.c. of the total organic acid (free phis combined) 

 present. In unconcentrated Sicilian juice the combined acid is about 7-9 

 p. c. of the total. Again, the English pressed juice contains hardly 

 any organic acid save citric only about 1 p. c. of the total organic acid 

 being unprecipitable as calcium citrate. In Sicilian juice about 8 p. c. 

 of the total organic acid is unprecipitable as calcium salt. 



The concentrated lemon juice from Sicily is reckoned of standard 

 quality when its sp. gr. is 1.24, and its acidity is equal to 64 oz. per 

 gallon of nominal citric acid. In dealing with trade analysis it must, 

 however, be borne in mind that the " crystallised citric acid" of a trade 

 certificate is not the crystallised acid of commerce, but an acid contain- 

 ing only half the actual amount of water, an acid in fact having the 

 atomic weight 201 instead of 210 



(0 6 H 8 7 H, O.) 

 no reason can be given for this practice, which should certainly be 

 abolished. In the present article all quantities of citric acid will be ex- 

 pressed in terms of the common crystallised acid. 



