On Citric Acid. ao 



and reserved for another purpose*. The precipitate was then 

 carefully washed with hot water from the worm-tub of the la- 

 boratory still, and this was drawn ofF'the next morning. It was 

 afterwards washed several times with cold water ; in all seven 

 times, the first vvasliing only !)eing with hot water. The water 

 which was drawn off at the third washing was considerably co- 

 loured. While the citrate of lime was precipitating completely, 

 after the last washing, and I allowed it due time to subside, in 

 order to separate as much as possible of the water which rested 

 on its surface, I drew oif into another vessel the contents of five 

 pipes more of lime-juice, v.'hich in the whole measured 450 gal- 

 lons. This quantity required 149 pounds of whiting for its com- 

 plete saturation f. 



The precipitate now obtained was treated and washed with 

 the same attention and care as tlie former, to separate the whole 

 of the malate and acetate;}; of lime, the extractive matter, and 

 the mucilage. Both the precipitates were then removed to a 

 leaden cistern, and 500 lbs. of soft water were poured on them, 

 which enabled us very thoroughly to mix the whole. 240 lbs. 

 of oil of vitriol of the specific gravity of 1-845 were now diluted 

 with 256 lbs. or 32 gallons, wine measure, of soft water, and this 

 diluted sulphuric acid was immediatclv, whilst hot from the mu- 

 tual action of the two fluids on each other, gradually poured in 

 successive portions into tlie leaden cistorn upon the above-men- 

 tioned mixture of citrate of lime and water. While this was 

 doing, two of the v/orkmen never ceased stirring up the whole 

 with large wooden spatulas, the more effectually to prevent any 

 part of the citrate from escaping the action of the sulphuric 

 acid. 



Notwithstanding this, I perceived that the precipitate conglo- 

 merated very much on everv addition of the sulphuric acid ; a 

 circumstance which was occasioned, as I afterwards discovered, 

 by using this acid in too concentrated a state. There is be- 

 sides another evil attending this ; for as sulphuric acid, fully 

 concentrated, will convert the citric into acetic acid, there will 

 always be a danger of lessening the ([uantity of the produce, vvhen 



• It was designed to separate tlie water by free7in^ or evaporation, and ihen 

 treat the remaining^ malic acid and mucilage with nitric acid, with the view of 

 obtaining; ox.ilic acid. 



+ Lime-juice is j!;enerally stronprer than that of lemons ; and when it is of the 

 full standard strength, it will take half a pound of chalk to every gallon of the 

 juice. , 



t It may be worth remarking, that ordinary juice not only takes less lime, 

 but that sometimes even a considerable portion of what is used does not remain 

 in the vat, for it is drawn ofT with the malic and acetic acids ; the malate and 

 ibc acetate of lime being both soluble salts. Hence the necessity of always eT.- 

 p'oying a chemical test to determine the quantity of sulphuric acid required for 

 ibe subsequent operarion. 



D 4 the 



