. On Citric Acid. . 109 



It is worthy of notice, that these tests may be employed, not 

 only in purchasing lime-juice, but also in ascertanimg the quan- 

 tify of real acid in acid liquors of different degrees of concentra- 

 tioii a matter of considerable consequence to those prmters who 

 ^desirous of being accurate in the proportion of acrd which 

 thev design to use in any particular style ol work. 



As sonfe of the calico-printers in the North of England have 

 found it advantageous to buy lemon-juice tor themselves, as men- 

 tioned at page 85, and use it, after it is concentrated by evapo- 

 at^n, wifhoutfu'ther purification, I would here take the op- 

 portunity of suggesting: that when the ju,ce has been part.ahy 

 "ncJnt?ated by being exposed for some time to a very moderate 

 heat it would be useful to remove it to a situation where the 

 evaporation will be suspended, and where it can remain un- 

 disturbed for a day or two, to give time for the thickened muci- 

 W* entirely to subside. It will then be advisable to draw the 

 fluid off from the precipitated impurities, by a syphon, or other 

 means, and to pass it through a filter before it be submitted to 

 any further process of concentration. i. . •. •„ * 



If it be treated in this manner,! am of opmion that itwdlnot 

 only be sufficiently concentrated, but that it w-ill also be suffi- 

 ciently pure for almost every purpose to which the calico-printer 

 can possibly have occasion to apply it. 



However, should the printer be desirous of purifying his juice 

 bv the chalk process, as described at page 12, 1 see no reason 

 why he may not evaporate the fluid by some such method as is 

 directed above, and use it in any stage of its concenti-ation that 

 may be most suitable, without being at the expense of reducing 



it to the solid form. . i ^ 1 1 r *i,^ 



To render this more easy, I have constructed a tab e of the 

 quantities of purified acid in a given portion of liquor of aifferent 

 strengths, J indicated by their specific gravity; and another 

 table of a similar nature for the unhmshed acid, or brown cry- 

 stalst which I presume will be used with more propriety than 

 the fo mer, whenever it is necessary to ascertain the quantity of 

 acid in the liquor of the first boiling. Both these tables will be 

 found in the subsequent pages marked No. IV. and V. 



• Foiircroy, who has esamlaed this precipitate, savs that "it is "ot^ simple 

 veJZe^JahKO, for that when dried it is not so uble m boiling water; tha 

 rft^reVtedrS^^^ it yields azotic gas, and is converted into m.hc and 



It treateu i)y i • . ■' j [ ^g ^^^^^ analogs with pluten. 



°"+"lt w k'nrcclli'hltt'he specific gravity of the solution .f brown cr,- 

 J. !s JeLer KL that of the pure' crystals. This I apprehend anses from the 

 brown cr^-stals generally retaining a portion of sulphuric ac.d. 



No. I. 



