On Citric Acid. 49 



he adopted merely the same method which he had employed to 

 purify and crystallize the tartaric acid. It consists in separating 

 the real acid by means of carbonate of lime, and then decom- 

 posing the citrate of lime by the intermedium of diluted sul- 

 phuric acid; a process which' has since been followed throughout 

 Europe ; for we have no other means of putting this acid into a 

 crystalline form. Having myself had some experience in this 

 process by frequently superintending its progress, and more than 

 once to the extent of several hogsheads' of juice in one opera- 

 tion, I shall now, with some confidence in their correctness, pro- 

 ceed to give what appear to me to be the best directions for ob- 

 taining ji successfid result. 



The juice, which is imported in pipes and hogsheads, should 

 be drawn off into a large open vessel] and a square vat made of 

 hr is very proper for the purpose. In this vessel the juice is to 

 be saturated with lime, by the gradual addition (lest the effer- 

 vescence by the disengagement of carbonic acid should occasion 

 an overflow) of clean soft ehalk, or whiting. Care must be taken 

 to note down the quantity of carbonate of lime employed, which 

 should be added till it occasions no further effervescence, and 

 until the liquor shows no signs of acidity on test paper. When 

 there is room, the better way would be to put the intended quan- 

 tity of whiting, or nearly the whole of it, all into the vat at first: 

 to wet It well with water, and then to pump in the acid by de- 

 grees upon it ; for in this way the effervescence h less, and the 

 operation more manageable. If the cask containing the juice 

 be rolled near to the vat, a small hand pump (of copper should 

 be preferred) may be put in at the bung-hole; and while one 

 man is slowly pumping it into the vat, another should not cease 

 to agitate the whiting ; and whenever there is any danger of the 

 mixture rising too high in the vessel, the operators will have 

 only to rest a moment, and all will be safe. B> this mode the 

 saturation will be complete, and it will be done in the least pos- 

 sible time. In this process all the real acid of the lemon juice 

 is absorbed by the calcareous earth ; and when the combination 

 is completely formed, the citrate of lime, which is an insoluble 

 salt, precipitates to the bottom of the vessel. When the whole 

 of this has fallen, the supernatant liquor, which is nearly tasteless, 

 will be found to contain nothing besides the mucilage, except a 

 portion of the essential oil of the rind of the fruit, some extrac- 

 tive and saccharine matter, and a little malic acid *. This su- 



• Were it deened neee'^sary for any part or the whole of tlie mnlic acid to be 

 «aved, It can readily be distinguished from the citric by the foUowine- properties: 

 I lie tr.alicacid does not Lrystillj/.e; it precipitates silver, morcvirv, and lead 

 from their solutions in nitnc acid, while citnc .icid hai ao such efFcct; and it 

 Jorm5 a snluldenh when combined with lime 



Vol. 4G. No. 207. July 1815. ' D pernatant 



