On Citric Acid. 103 



lemon on a lump of sugar. The sugar, by imbibing the volatile 

 oil of the lemon, renders it soluble*. 



Other domestic and oeconomical purposes might be enume- 

 rated to which citric acid is applicable, especially now that it 

 can be kept in its crystallized state, in every family, and that it 

 is in such form liable neither to total decay nor even the slightest 

 alteration. 



An aceto-citric acid has been much employed in various pro- 

 cesses of dyeing by Mr. Guhliche. He calls it vegetable acid 

 spirit, and prepares it in the following manner: 



He takes any quantity of lemons (those of which the rind is 

 decayed will do), he removes the peel and the skin that adheres 

 to it, and slices them into a vessel, which ought not to be made 

 of wood. He then sprinkles them with a quantity of good vine- 

 gar; squeezes out the juice through a flannel, by means of a 

 press, and filtrates the expressed liquor through paper. It may 

 be used in this state ; but as it is apt to grow mouldy, he directs 

 it to be purified and concentrated as follows : 



The liquor is to be exposed to the sun, until it forms a sedi- 

 ment, and grows clear. It is then to be filtrated, and distilled in 

 a sand-bath. The receiver is to be changed when the Hquor 

 that drops becomes acid, and the distillation continued till oily 

 streaks are perceptible in the neck of the retort. The acid now 

 found in the receiver is to be kept for use. 



The largest quantity of citric acid is consumed by the calico- 

 printer, who uses it in several processes of his art, especially to 

 discharge iroi>, and to preserve white grounds on certain parts 

 of any pattern, by means of the property it has of resisting the 

 operation of sundry dyes, as is more fully explained in the Essay 

 on Calico-printing. 



The person who first prepared this acid in large quantities in 

 England, and principally for the use of the calico-printers, was 

 Mr. Coxwell, late of Fleet-street, who sold it at a high price, in 

 the form of neat white crystals. With this the printers were 

 supplied for many years ; but when the demand became greater 

 than he could well answer, he began to finnish them with the 

 brown crystals, that is, with the acid in the first stage of cry- 

 stallization, and consequently at a much more reasonable price. 



This urged the printers pretty generally to turn their attention 

 to the preparation of the citric acid ; and now most of the houses 



* By this means it is easy to preserve the volatile oil of any number of lemons. 

 The oleosaccharum thus obtained, may he mixed in a mortar with a sufficient 

 quantity of sugar; and when this has been dried by a very gentle heat, it may 

 be kept in well stopped bottles, unimpaired, for any length of time. This is 

 preferable to the volatile oil of lemons, obtained by distillation, for the fire ge- 

 nerally imparts an unpleasant or empyreumatic flavour to this and most other 

 etfecntial oils. 



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