264 



quoted at so much per pipe these standard quantities are assumed. In 

 reality these quotations refer to an arbitrary quantity of 432 pounds of 

 citric acid. In the production of concentrated lime juice in the West 

 Indies it has been the practice to carry the concentration to a higher 

 degree than this, so that concentrated lime juice usually contains upwards 

 of 96 ounces per gallon ; a good rule in practice is to endeavour to pro- 

 duce concentrated juice which will have a uniform specific gravity of 

 about 1'300. In dealing with lime and lemon juices a particular 

 form of hydrometer, known as a oitrometer is frequently made use of, 

 though its use is less common than formerly. Knowledge of the or- 

 igin of its scale and the meaning of its indications appears to have 

 been lost ; from experiments which I made some years ago I came to 

 the conclusion that the instrument is so constructed that when placed 

 in hot (boiling) lemon juice it will indicate the same degree as a Twad- 

 del's hydrometer will show when floating in the same juice in the cold. 

 It is thus a useful instrument in the hands of the man in charge of 

 the concentrating pans, for he can from time to time test the juice 

 rapidly, in a hot condition, and arrest the boiling when the citrometer 

 indicates the same degree which on a Twaddel's instrument will corres- 

 pond to the specific gravity 1'300 ; this of course is 60^^. Hence the 

 rule for concentrating becomes : — Carry on the concentration until the 

 citrometer, when immersed in the juice at the boiling temperature, shows 

 a density of 60°. The product thus obtained is a dark, nearly black, 

 thick liquid. 



It is often urged that there is very considerable loss of citric acid 

 when juice is treated in this manner. My own experiments lead me 

 to suppose that when juice of good quality is treated, the loss is about 

 7 to 8 per cent, of the original acid; wh«n juice of poor quality is dealt 

 with, this loss may reach 10 or 12 per cent, probably owing to the 

 greater length of time required to concentrate the poorer juice to the 

 required density. If concentration is carried beyond the point indi- 

 cated the loss rapidly increases. The concentration here recommended 

 is that which I believe to afford the maximum concentration with the 

 minimum loss of acid. 



The concentrated juice should be thoroughly cooled before being 

 placed in casks or the casks will leak : indeed leakage from the casks 

 is one of th« most serious troubles which the maker of concentrated 

 juice has to contend with. Casks containing 54 gallons are usually 

 employed. 



The suggestion that the concentration of the juice should be con- 

 ducted in steam heated evaporators naturally occurs : it is open to ques- 

 tion whether these would offer such advantages as would compensate 

 for the increased complication and expense of the plant : the loss of 

 acid from over heating might be reduced somewhat. Only when the 

 manufacture is conducted on a very large scale will the question of the 

 use of steam evaporators arise, and here it might be desirable to con- 

 duct the first part of the evaporation over an open fire, while finishing 

 the evaporation of the thick juice in steam heated pans. 



The process as now conducted is a simple one, its defects are that it 

 necessitates the employment of a considerable quantity of fuel, it in- 

 volves the less of about 8 per cent, of acid, the product is dark in 

 colour, is liable to leak from the casks and requires expensive packages. 



