Preparation of the Citric Acid. no, 



already feen, form an obftacle to Us eryftallization, it might 

 not be pofiible to complete its purification either by concen- 

 tration alone, or by the aid of a little fpirit of wine ? Experi- 

 ments of this kind ought to be undertaken in a warm coun- 

 try, and on a fomevvhat large fcale, if it be required to obtain 

 more certain refults than thole which I was able to obtain in 

 Caftille. 



As the citric acid, when cryftallized, poflefies a very active 

 acidity, it appeared to me of importance to compare lemonade 

 made with thefe cryftals with that made by ufing the frefh 

 juice. I therefore firit took the juice of a lemon, and endea- 

 voured, by repeated trial, to dilcover what quantity of it in 

 weight it would require to make a large glafs of lemonade 

 well feafoned with fugar. The quantity requifite was about 

 right or nine drams. 



We have already feen that an ounce of juice employed for 

 experiments contained about 34 grains of citric acid, with a 

 fmall portion of malic acid, I therefore made a glafs of le- 

 monade, of the like fize, with the fame dofe of fugar and 

 54 grains of citric acid. The lemonade was of fuch a nature 

 that thofe called in to compare them could find no differ* 

 ence, except that there was fomething more agreeable in the 

 latter than in the former. At firft they could not tell in 

 what this difference confided ; but each of thole prefent 

 having tafted them feveral times, it was at length agreed that 

 the firil lemonade has a flight harmneis not obferved in the 

 lemonade made from the citric acid. 



This difference was afcribed, and very properly, to the 

 fmall quantity of aftringent principle in the lemon juice. 

 The addition, indeed, of fome drops of iron in freth lemon 

 juice, fat u rated afterwards by potafh, made it affume that 

 vinous colour which is obferved in old lemon juice. 



It is to the aftringent part of the lemons, without doubt, 

 that we mull afcribe that contraction of the abdomen which 

 people very often experience after drinking lemonade, Hence 

 it follows, that in difeafes where this contraction is to be- 

 apprehended, lemonade made with citric acid ought to be 

 preferred. 



I (hall conclude this memoir with the means of preventing 

 an accident which mav take place in the procefs followed 

 in regard to the citric acid. 



If more fulphuric acid than is neceffary to faturate the 

 bafe of the citrate has been employed, when this acid has 

 concentrated itfelf by evaporation, it will react on the citric 

 acid, and proceed fo far as to feparate fome carbonaceous 

 principles ; the mixture, becoming blacker and blacker, will 



H 4 refufe 



